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The Radio Thin Client Module (RTCM) is commercially available hardware for interfacing radios to an AllStarLink computer.
= Introduction =


The Micro-Node RTCM and VOTER interfaces are typically used with AllStar in voting/simulcast applications. They MAY be used for ANY repeater interface application, through the chan_voter channel driver. The VOTER is the original through-hole board designed by Jim Dixon for this application. It is open-source, and the relevant Gerber files and BoM to build it are available. The [http://www.micro-node.com/thin-m1.shtml Micro-Node Radio Thin Client Module (RTCM)] is the commercial version of the VOTER. It uses surface mount parts (SMT), but is functionally equivalent to the original VOTER. In general, the two terms (RTCM/VOTER) are used interchangeably, as they operate the same, and use the same firmware (mostly, see below).
The Radio Thin Client Module (RTCM) is [http://www.micro-node.com/thin-m1.shtml commercially available] hardware for interfacing radios to an AllStarLink computer.


This page will highlight some of the operational concerns, quirks, bugs, and other items of interest that relate to these interfaces. Much of the information has been gleaned off the AllStar mail list, comes from personal experience, or comes from notes in the firmware source code.
<gallery mode=nolines>
File:Rtcm2-750.jpg
File:Rtcm1-750.jpg
File:Rtcm3-750.jpg
</gallery>


=Testing=
The Micro-Node RTCM (and [[VOTER-Hardware | VOTER]]) interfaces are typically used with AllStar in voting/simulcast applications. They '''MAY''' be used for '''ANY''' repeater interface application, through the <code>chan_voter</code> channel driver, as they are primarily a Radio over IP (ROIP) adapter.  
RTCM's come preconfigured to login to [http://voter-demo-allstarlink.org voter-demo-allstarlink.org] for out of the box testing.


=Factory Reset=
The [[VOTER]] is the original [[VOTER-Hardware | through-hole board]] designed by Jim Dixon (SK) for this application. It is open-source, and the relevant Gerber files and BoM to build it are [https://github.com/AllStarLink/Voter/blob/master/VOTER-pcb/voter-cad-rev-a.zip available].  
A factory reset can be performed by setting SW 1 down and then applying power to the RTCM. Wait for the green LED to stop blinking, power off and set SW 1 back up.  


The [http://www.micro-node.com/thin-m1.shtml Micro-Node Radio Thin Client Module (RTCM)] is the commercial version of the VOTER. It uses surface mount parts (SMT), but is functionally equivalent to the original [[VOTER-Hardware | VOTER]]. In general, the two terms (RTCM/VOTER) are used interchangeably, as they operate the same, and use the same firmware (mostly, see below).


==Chuck Squelch==
If you want to enable "Chuck Squelch", open the HardwareProfile.h and un-comment #define CHUCK.


= Firmware =


You may also want to go down to Line 291 in Voter.c (right click on the window, go to Properties --> "C" File Types --> Line Numbers) and tack on CHUCK after 1.60 (the current version number) so that when you load this firmware, the version will be shown as 1.51CHUCK, and you'll know that Chuck Squelch is compiled in. We should probably make that more automagic in the future...
See the [[RTCM_Firmware_upgrading | firmware upgrade]] page for information on upgrading the firmware.




==DSP/BEW==
= Board Layout =
If you want to compile the DSPBEW version, open the DSPBEW project file instead.


== Connectors and Switches ==


=DSP/BEW Firmware Version=
DSP BEW Firmware is mutually exclusive with the diagnostic menu. There is not enough space for both, if you load the DSP/BEW firmware, you will '''NOT''' have a diag menu.
BEW stands for Baseband Examination Window.
Typically, the discriminator of an FM communications receiver produces results containing audio spectrum from the "sub-audible" range (typically < 100 Hz) to well above frequencies able to be produced by modulating audio. These higher frequencies can be utilized to determine signal quality, since they can only contain noise (or no noise, if a sufficiently strong signal is present).
For receivers (such as the Motorola Quantar, etc) that do not provide sufficient spectral content at these "noise" frequencies (for various reasons), The "DSP/BEW (Digital Signal Processor / Baseband Examination Window)" feature of the RTCM firmware may be utilized.
These receivers are perfectly capable of providing valid "noise" signal with no modulation on the input of the receiver, but with strong modulation (high frequency audio and high deviation), it severely interferes with proper analysis of signal strength.
This feature provides a means by which a "Window" of baseband (normal audio range) signal is examined by a DSP and a determination of whether or not sufficient audio is present to cause interference of proper signal strength is made. During the VERY brief periods of time when it is determined that sufficient audio is present to cause interference, the signal strength value is "held" (the last valid value previous to the time of interference) until such time that the interfering audio is no longer present. 
The DSP/BEW feature is selectable, and '''should not''' be used for a receiver that does not need it.
A note on the Motorola SLR5700 per VE7FET. DSP/BEW definitely makes a difference on what AllMon reports for the signal strength of received signals. It is less reactive when DSP/BEW = 1 than with it set to 0. We'll have to see what the real world trials show. It might be better to leave it off.
=Chuck Squelch=
"Chuck Squelch" are a couple firmware changes made by Chuck Henderson, WB9UUS.
Pre-compiled firmware versions including this option are available on [https://github.com/AllStarLink/voter/tree/master/board-firmware GitHub]. See above on how it is enabled/compiled, if you are rolling your own firmware modifications.
One of the changes fixes an issue with weak signals producing RSSI readings all over the place. It is caused by a 16 bit value that was overflowing (it is the RSSI change in the firmware). It results in rock-solid RSSI values being reported, even on barely or non-readable signals. '''This change will likely be rolled in to a permanent fix in a future firmware release.'''
The other firmware change changes how the squelch responds (looks at the noise in the last two audio samples) and makes the "Micor squelch" action work better.
You may also want to consider the following changes in [[Voter.conf|/etc/asterisk/voter.conf]]:
<pre>
;Comment out:
;thresholds =
;and set:
linger = 0
</pre>
=Squelch Issues=
*If anyone is off frequency a little bit, that will make the voice talk off worse. Double check that the repeater and the users are all on frequency.
*Don't use narrow bandwidth on the repeater receiver.
*Make sure that the discriminator audio is not rolled off even a little bit at the high end. There should not be resistors in series or capacitors to ground between the discriminator chip output pin and the voter board input, for best results.
==Motorola Quantar==
Some things to consider:
*Install JP1 on the Quantar's RTCM. The squelch should calibrate at around 4 blinks rather than the 12 blinks or so without JP1.
*Be sure you've done the diode and squelch calibration with the actual attached radio (no antenna).
*The Quantar firmware should be 20.14.48 as later versions have better noise output.
*Try the "Chuck Squelch" RTCM version.
*Each RTCM should have 3 to 5 turns past threshold to prevent the squelch form being too loose. Somewhere around the 350 level seems about right. Chuck Squelch seems to need fewer turns but YMMV.
*Don't "and" CTCSS with squelch. That may override the RTCM's squelch detection. Compare with CTCSS on and off to see effect if any.
Also check the [[Quantar_RTCM|Quantar RTCM]] page for detailed interfacing and configuration information.
=RTCM/VOTER LED's=
RX LED on the RTCM/VOTER will flash (same rate as ACT LED) if you have External CTCSS enabled, and the received signal has the wrong (or no) valid PL.
=Network Information=
==RTCM/VOTER Bandwidth==
Assuming ulaw... The RTCM will require approximately 80kbps of bandwidth for continual usage.
==Network Quality==
Your IP Network quality is important. You may wish to add a rule in your routers to prioritize traffic on UDP port 667 so that RTCM audio is given priority over other
traffic. Also see the [[#Debug Options]] below for notes on how to tag your packets with ToS.
==RX/TX Buffers are NOT Both Millisecond Values==
You might assume an RX buffer (in voter.conf) of 120ms would be equivalent of a TX buffer (in the RTCM) of 120ms. That is not the case.
The TX buffer is a number of 125 '''microsecond''' intervals, where the RX buffer is in milliseconds.
If you follow the buffer setting instructions, you should be fine, in most cases.
=Audio=
The RTCM/VOTER is totally flexible regarding emphasis. Although the way it is set is completely obscure. It tries to automatically do the right thing for you, which is great most of the time. But when it’s not, it's hard to know what is going on.
If you are changing the COR Type settings, or nodeemp in voter.conf, make sure you save/reboot the RTCM/VOTER every time you make a change... changes are '''not''' effective until the RTCM/VOTER reboots!
==Voting==
Before we get in to the different ways audio is routed, there is an important consideration you need to make if you are using the RTCM/VOTER for voting.
The way the voting process works, it needs '''discriminator audio''' to determine the signal to noise level from each satellite receiver. As such, you will need to be feeding discriminator audio in to the RX audio pin, so that the hardware/software can vote properly. That means you also need to let the hardware/software do the squelch action.
If you need RX CTCSS, you'll need to feed logic from an external CTCSS decoder in to the CTCSS input pin.
Also, don't disable COR in the RTCM/VOTER... it will cause it to disable the squelch and it will report an RSSI of 255 (full quieting) for all received signals.
==Receiver De-emphasis==
On the RX side the COR Type setting in the RTCM/VOTER determines whether the de-emphasis filter is used for RX audio. 0=Normal means the RTCM/VOTER squelch circuit is in use and it is expecting discriminator audio on the RX pin (to be able to do the squelch action), and therefore it '''will''' provide de-emphasis (audio is routed THROUGH the de-emphasis RC filter circuit) to the receiver audio. COR Type 1=IGNORE COR uses the CTCSS input pin for COR or CTCSS ''logic'' and it then expects de-emphasized receive (line) audio on the RX pin, and therefore will '''not''' provide de-emphasis to the received audio (the RC filter is switched '''out''' and audio passes straight through).
Most of the time, you do NOT need to override the automatic filter selection. However, if you do, and you are sure you have a good reason to, you CAN switch the de-emphasis filter '''out''' of the circuit so that audio passes straight through to the encoder. You would do this by setting the nodeemp=1 option in voter.conf. When you set nodeemp=1, the ''VOTER Protocol'' tells the RTCM/VOTER to switch the filter '''out''', so audio is passed straight through.
==Transmitter Pre-emhpasis==
On the TX side, the RTCM/VOTER expects the repeater to accept ''mic audio''. In other words, the '''repeater''' is providing the pre-emphasis, not the RTCM/VOTER (you are '''not''' directly modulating the TX). This can be overridden by setting CTCSS tone in voter.conf. If a CTCSS tone is defined, the RTCM '''will''' provide pre-emphasis to the audio, and expects that you will be connecting to your repeater's flat audio input (direct modulation).
If you don’t want TX CTCSS tone but '''do''' need pre-emphasis, set an arbitrary (any) CTCSS tone in voter.conf, and set the level to 0. This will force the RTCM/VOTER to pre-emphasize the audio it generates on the TX pin, but it won't actually mix in a CTCSS tone.
==Level Setting==
Setting the audio levels for the RTCM/VOTER is pretty straight forward. Just follow these steps:
*Ensure you have a connection to your host Asterisk server/chan_voter instance
*Send a 1kHz@3kHz on-channel, full-quieting signal in to the repeater's RX
*Set the RX up so it reads 3kHz deviation on the RTCM's built in console meter
*Now set the TX level '''pot''' to get 3kHz out of the transmitter (No PL)
Now change the modulation from 1kHz tone to 800Hz followed by 1.8kHz and verify that the deviation level doesn't change as the tone frequency changes. '''Changing levels indicates a pre/de-emphasis issue.''' You will want to read the above sections on how audio is handled, and figure out where your issue is.
If using PL you have to account for that deviation, unless you filter it out with your IFR (test set).
That's it!
Optionally, if you are using the built-in "offline repeat" functions, fail the connection to the host Asterisk server, and make sure your repeat audio performs the same as above.
==== Resolution issues when setting levels using built VOTER boards ====
Sometimes, depending on what radio is being used getting a good enough resolution with R61 when setting levels is a problem. You move a small amount on the pot and it jumps several hundred KHz of deviation. Inserting a 4:1 voltage divider between the VOTER board and transmitter helps with this. Something such as a 1K and 330 ohm resistor will work. This allows for much finer adjustment on the transmit audio (R61).
==Crappy Transmit Audio==
Does your repeated audio sounded really bassy, muffled, and not very understandable?
There was a situation where, compared to a typical simplex radio-to-radio transmission, the audio through the repeater (RTCM and Asterisk) was unacceptable. What was discovered was that the RTCM has an internal pre-emphasis function that was disabled. The user had intentionally disabled "txctcss" and "txctcsslevel" in voter.conf because he didn't
want the RTCM transmitting CTCSS (the Quantar was doing that already). He ultimately found a post on the mail list explaining the settings above that said enabling txctcss = some valid tone (114.8 in his case) and setting txctcsslevel = 0 would turn on the pre-emphasis function in the RTCM without transmitting CTCSS tones.
He did, and it worked like a charm! Audio now had more treble and was less bassy/muffled. So, future RTCM users, be sure not to comment out txctcss and txctcsslevel in voter.conf!
Just enable and set the level to 0. You'll thank me later.
== Pulse Noise on Transmit Audio ==
It has been noticed sometimes on built VOTER boards that it has low level DAC noise which sometimes is apparent as a pulsing noise on the audio output. Adding a 4:1 voltage divider inline between the transmitter and VOTER board helps reduce or eliminate this as described above in Level setting.
=GPS=
The RTCM/VOTER will work with most GPS available. It requires either NMEA or Trimble TSIP binary data. It only receives data '''from''' the GPS (GPS TX), it does not send anything '''to''' the GPS.
The firmware is specifically written to talk to Trimble Thunderbolt receivers using Trimble's TSIP binary data interface, however, other Trimbles GPS receivers that talk TSIP are generally compatible.
==RTCM GPS Connections==
There are some quirks specific to the RTCM that are not well documented.
The GPS connections for the RTCM are on the DB15 connector. Note that the labels for GTX and GRX are misleading. GTX is the data '''FROM''' the GPS '''TO''' the RTCM (GPS TX/RTCM RX). GRX is data from the RTCM to the GPS, but that is currently not used, so it does not need to be connected.
PPS is obvious, that is your PPS signal from your GPS.
Also note, inside the RTCM, there are jumpers to set for TTL or RS-232 data, depending on the type of GPS you are connecting. Set them accordingly. The RS-232 setting loops the data through a MAX3232 converter on the board.
You will still need to set the data and PPS polarity, and baud rate in the configuration menus to get everything to work.
==NMEA Sentences==
If you are using an NMEA GPS (as opposed to a Trimble using the TSIP binary interface), the RTCM/VOTER is looking for the following NMEA sentences:
<pre>
$GPGGA
$GPGSV
$GPRMC
</pre>
==GPS Lock==
The GPS led will go solid regardless of the connection LED. That '''has''' to happen or it won't connect to the Asterisk server.
It is not unusual for it to take up to 20 mins to get a GPS lock LED (ie. using a Trimble Thunderbolt) after any reboot.
==GPS De-sense==
If you are having odd loss of lock issues, consider you may have interference to your GPS antenna from strong RF nearby. A note from Jesse Lloyd:
<pre>
I also had crazy problems with poor signal on my GPS when I set it up sitting in a window, and once installed at site I had the GPS antenna maybe 6 ft from the VHF antenna, and after some troubleshooting found it was getting swamped with RF and loosing lock.
I found the debug setting of 32 useful in the RTCM, you can see a hex output of the GPS status. 
</pre>
==GPS Issues==
===Trimble Thunderbolt===
You may find your Trimble Thunderbolt is showing the incorrect date at the moment. It could be showing the year as 1997. This is due to the date in the Thunderbolt being reported incorrectly.
'''This can cause some of your voting receivers to not connect, if they are used with other GPS in your system.''' If you have '''ALL''' Thunderbolts, or '''NO''' Thunderbolts, you are probably fine. If you have '''ALL''' Thunderbolts, the date/time is probably wrong, but they will ALL be wrong, so they will connect.
GPS Time is a continuous counting time scale beginning at the January 5, 1980 to January 6, 1980 midnight. It is split into two parts: a time of week measured in seconds from midnight Sat/Sun and a week number. The time of week is transmitted in an unambiguous manner by the satellites, but only the bottom 10 bits of the week number are transmitted. This means that a receiver will see a week number count that goes up steadily until it reaches 1023 after which it will “roll over” back to zero, before steadily going up again. Such a week rollover will occur approx. every 20 years. The last week rollover occurred in 1999 and the next one will be in 2019.
The Thunderbolt manual states:
<pre>
<pre>
The ThunderBolt adjusts for this week rollover by adding 1024 to any week number reported by GPS which is less than week number 936 which began on December 14, 1997. With this technique, the ThunderBolt will provide an accurate translation of GPS week number and TOW to time and date until July 30, 2017.
J1    - ICSP Programming Header
P1    - Radio
P2    - Console/GPS
SW1  - Reset (Momentary)
SW2-1 - Init EEPROM
SW2-2 - Calibrate Squelch
SW2-3 - Calibrate Diode
SW2-4 - RX Level LEDs
</pre>
</pre>




As such, the Trimble Thunderbolt has a firmware issue with the GPS Week rollover that manifested itself on July 30, 2017, causing the date to become incorrect. The Thunderbolt thinks the week changed from 935 to 936 (actual week 1959-1024=935), so it stopped adding 1024 to the week.
=== J1 - ICSP Programming Header (6 pin MTA-100) ===
 
 
We have added a brute-force fix starting in RTCM/VOTER firmware >=1.51. This fix adds 619315200 seconds (1024 weeks) to the time reported by the GPS. It fixes the Thunderbolts, we have not done extensive testing to see how it affects other TSIP receivers.
 
 
===Garmin===
====Garmin 18x LVC Wiring Issues====
If you have issues with your GPS 18x LVC not talking to the RTCM/VOTER, it may not be hooked up to the RTCM correctly.
 
 
The Garmin pin labeling is backwards to what you may think. See below. You probably need to swap pins 6 and 14.


<pre>
<pre>
RTCM                  GPS 18x LVC     
1 - MCLR
6 GRX <-- Rx Data 6 Green 
2 - +3.3Vdc
7 GPPS <-- Pulse Output 1 Yellow 
3 - GND
8 GND  Ground 3 Black 
4 - PGD (Program Data)
8 GND   Ground 5 Black 
5 - PGC (Program Clock)
13 +5V -->Vin 2 Red 
6 – NU
14 GTX --> TX Data 4 White
</pre>
</pre>




Log into the RTCM and do 98 and you should see something like this:
=== P1 - Radio Connector Pinout (DB9 Male) ===


<pre>
<pre>
Current Time: Sun  Apr 20, 2014  04:37:02.820
1 - + VIn (7-24 Volts DC).
Last Rx Pkt System time: 04/20/2014 03:55:35.580, diff: 2487260 msec
2 - Transmit Audio Out
Last Rx Pkt Timestamp time: 04/20/2014 03:55:32.064, diff: 3515 msec
3 - Receive (discriminator) Audio In
Last Rx Pkt index: 160, inbounds: 1
4 - External CTCSS Input (optional)
5 - Gnd
6 - Gnd
7 - /PTT Out (open-collector, active-low)
8 - Gnd
9 – Gnd
</pre>
</pre>




====Garmin and the RTCM====
=== P2 - Console/GPS Connector Pinout (DB15 Female) ===
Beware when buying newer Garmin GPS's to use with the Micro-Node RTCM.
 
 
The RTCM expects a 5V PPS signal.
 
 
Newer Garmin's (GPS 18X, 18X LVC, etc.) MAY NOT output 5V, and can cause issues. '''Check the Garmin datasheet'''.
 
 
The VOTER is designed to accept both 3.3V or 5V signals, and ''should'' work fine.
 
* Some of the Garmin GPS's come with 4800 baud set as default. If you are getting a "Warning: GPS Data time period elapsed" error on your RTCM, change both the GPS and RTCM to use 9600 baud. To do this, interface the GPS to a DB9 connector as per page 8 of the [http://wiki.allstarlink.org/w/images/4/41/GPS_18x_Tech_Specs.pdf manual] (remembering to ONLY use 5V as the power source *facepalm*). Once done, download, extract and open [http://www8.garmin.com/support/download_details.jsp?id=4053 SNSRXCFG_330.exe] and run.
# Select your GPS (in most cases GPS 18x PC/LVC). Press F10 to switch to NMEA mode (Config > Switch to NMEA Mode)
# Select Config > Setup and choose the COM port your GPS is connected too. Leave baud rate as auto for now, OK.
# Select Comm > Connect to connect to the GPS.
# Go to Config > Get Configuration from GPS to download it's current configuration
# Click File > Save to save the current configuration
# In Config > Sensor Configuration change the Baud Rate to 9600. You can also check to make sure 1PPS is enabled here too. Click OK.
# Hitting F7 when in the main window of the software also brings up the GPS sentences to output if that is of interest.
# File > Save to a different file than step 5.
# Press F9 or Config > Send Configuration to GPS. This will then send all the changes you made to the GPS unit (including baud rate so a reconnect may be needed)
 
 
===uBlox GPS===
You can use uBlox GPS modules with the VOTER/RTCM. The ones readily available usually have a 5 pin header on them (5V, GND, TXD, RXD, PPS), as well as an integrated patch antenna, and a SMA connector for an external antenna.
 
 
Data is TTL, so make sure to set the jumpers inside the RTCM for TTL data. Baud rate is 9600 by default, and uses NMEA. Set those accordingly in the configuration menu.
 
 
The RTCM and VOTER require different settings for data and PPS polarity. The VOTER wants '''inverted''' for both, and the RTCM wants '''non-inverted''' for both.
 
 
Make sure to save (99) and reboot (r) your VOTER/RTCM after making changes for them to be effective.
 
 
==No GPS/Mixed Mode==
You do not need a timing source to use an RTCM if you don’t want to vote. That’s called Mix Mode.
 
 
Having the PPS Polarity set to 2 tells the RTCM you do not have a GPS. That forces the RTCM to become a mix (non-voting) client. Turn it on, save it, and restart. A simple voter.conf would look like this:
 
<pre>
[general]
port = 667
password = BLAH
 
[1000]
Site1 = pswrd1,master,transmit
Site2 = pswrd2,transmit
</pre>
 


==Mixed Client Error==
"I am getting this error in Asterisk":
<pre>
<pre>
WARNING[2368]: chan_voter.c:4511 voter_reader: Voter client master timing source mobile1 attempting to authenticate as mix client!!
1 - NC
2 - Console Transmit Data
3 - Console Receive Data
4 - NC
5 - Gnd
6 - GPS Receive Data
7 - PTT Out
8 - Gnd
9 - NC
10 - Console Request To Send (RTS)
11 - Console Clear To Send (CTS)
12 - NC
13 - GPS Power Output (5Vdc @ 800ma MAX)
14 - GPS Transmit Data
15 – External Reset
</pre>
</pre>




A mixed client error means the voter.conf file is expecting an RTCM to try and connect with a GPS IP packet (ie. has '''master''' in it in voter.conf), but the RTCM isn't
=== SW1 - Reset ===
sending a GPS IP packet. So its a mismatch between voter.conf and Option 10 in the RTCM.
 
 
If you want to use a mix client (non-voted), make sure that receiver's configuration line in voter.conf '''does not''' have the '''master''' option set.
 


==Mix Clients with Voted Client Issues==
Depress SW1 momentarily to reset the RTCM.


Situation...
"I have a private node with 6 voted receivers using RTCMs. I'd like to add a 7th RTCM to this node that is always mixed in rather than voted. I'm able to make this RTCM work as a 7th voted receiver with no problem. Everything I've read seems to indicate that if I change GPS PPS polarity to "none" this will achieve my desired results, however I am unable to get audio out of my transmit RTCM from this 7th site. It does change color to cyan in Allmon indicating it is non voted input but I do not get any indication or audio when that units COR goes active."


"Setting voter debug level 3 in Asterisk and I'm seeing the following message repeatedly scrolling by in a blur when the mix client detects COR (COR is active). Sequence numbers are continually incrementing by 1. I'm running software version 1.47 on all my clients:"
=== SW2 - DIP Switch ===


<pre>
<pre>
mix client (Mulaw) my_client index:0 their seq:629 our seq:629
SW2-1 - Init EEPROM
mix client my_client outa bounds, resetting!!
SW2-2 - Calibrate Squelch
SW2-3 - Calibrate Diode
SW2-4 - RX Level LEDs
</pre>
</pre>


If you have a similar situation to the above... check your buflen in voter.conf. Make sure it is at >=160 and see if that fixes it.


SW2-1 "Initialize configuration parameters in EEPROM" (factory reset). If ON when firmware starts, the operating parameters in the EEPROM will be set to default values. The system activity LED (LD1, green) will stay off for aproximately 4 seconds, then stay on steady to indicate that the initialization process is complete. Afterwards, the switch may be TURNED OFF and the system will continue running normally. Note, if SW2-3 is ON during this procedure, the “Diode Calibration” process will also occur.


==GPS Debug==
To turn on GPS Debugging, set the Debug Option Level in the RTCM/VOTER to 32.


SW2-2 On to calibrate squelch. With the receiver connected and its antenna removed, switch on SW2-2. In the next few seconds the "Receive Signal Indicator" (LD3, Green) will flash on and off, then (hopefully) on steady. This indicates that the squelch calibration has occurred successfully. If unsuccessful, the LED will flash either fast to indicate that the discriminator noise level is too high, or slowly to indicate that the discriminator noise level is too low. Note, if SW2-3 is ON during this procedure, the "Diode Calibration" process will also occur.


See [[#Debug Options]] levels for more information on how this works.


SW2-3 On to perform "Diode Calibration". This may only be done in conjunction with a configuration parameter initialization (see SW2-1, above), or a "Squelch Calibration" (see SW2-2, above).


==Trimble Debug Status Decoding==
The VOTER/RTCM when in TSIP mode (Trimble), assumes it is a Trimble Thunderbolt and is looking for two packets:
*0x8F-AB - Primary Timing Packet
*0x8F-AC - Supplemental Timing Packet


SW2-4 On to temporarily re-purpose LD4 and LD5 to allow for visual indication of RX input level. With SW2-4 on, LD5 will indicate (by brightness) if the RX level is too low, and LD4 will indicate (by brightness) if the RX level is too high. So the idea is to tune R36 so that there is minimal brightness on both LD4 and LD5 (like a null, more or less). Alternatively, [[VOTER-Menus#97_RX_Level_Display | Menu 97]] on the console gives a more graphical method of setting the Rx input level.


Grab a copy of the Thunderbolt User Guide: http://leapsecond.com/pages/tbolt/Thunderbolt-2012-02.pdf


 
== LED Designations ==
Pages 78-83 are the important ones.
 
 
Packet 0x8F-AB is what grabs the timing information, and packet 0x8F-AC is what it looks at for everything else (including debug).
 
 
The debug string that the VOTER/RTCM reports:


<pre>
<pre>
printf("GPS-DEBUG: TSIP: ok %d, 9 - 14: %02x %02x %02x %02x %02x %02x\n",
LD1 - Heartbeat
happy,gps_buf[9],gps_buf[10],gps_buf[11],gps_buf[12],gps_buf[13],gps_buf[14]);
LD2 - PTT
LD3 - COS On solid is valid Rx signal, flashing is without CTCSS
LD4 - GPS On solid is GPS received and locked, flashing is GPS received, lock in progress
LD5 - HOST
</pre>
</pre>




So, the 1 after ok is the "happy gps" flag. The other 5 bytes are supposed to be bytes 9-14 from the packet... sort of. They are bytes 9-14 of the buffer, but they are actually bytes 8-13 of the binary message.
The COS (RX) LED on the RTCM will flash (same rate as Heartbeat LED) if you have External CTCSS enabled, and the received signal has the wrong (or no) valid PL.
 
 
Looking at the message structure, bytes 8-13 are:
*8-9 Critical Alarms
*10-11 Minor Alarms
*12 GPS Decoding Status
*13 Disciplining Activity




Therefore, the messages you are seeing break down as follows:
== Jumpers ==


<pre>
<pre>
GPS-DEBUG: TSIP: ok 1, 9 - 14: 00 00 00 00 00 00 - everything is good in the 'hood, Doing Fixes, Phase Locking
JP1 - Discriminator Level Boost
 
JP2 - 20dB Pad
GPS-DEBUG: TSIP: ok 0, 9 - 14: 00 00 00 18 08 06 - not happy, Not Tracking Satellites, Not Disciplining Oscillator (0x18 --> 0b000000011000), No Usable Sats, Inactive
JP3 - Output Amp Power Source
 
JP4 - GPS TX RS-232/TTL Select
GPS-DEBUG: TSIP: ok 0, 9 - 14: 00 00 00 08 08 05 - not happy, Not Tracking Satellites, No Useable Sats, Compensating OXCO (holdover)
JP5 - GPS RX RS-232/TTL Select
 
JP6 - Not Used
GPS-DEBUG: TSIP: ok 0, 9 - 14: 00 00 00 00 00 05 - not happy, Compensating OXCO (holdover)
JP7 - Bootloader Programming
 
GPS-DEBUG: TSIP: ok 1, 9 - 14: 00 00 00 00 00 08 - happy, Recovery Mode
 
GPS-DEBUG: TSIP: ok 0, 9 - 14: 00 00 00 00 00 04 - not happy, Initializing Loop Filter
</pre>
 
 
The GPS is flagged as NOT HAPPY in TSIP mode if ANY of the following are TRUE:
*If GPS Decoding Status is anything other than "Doing Fixes".
*If Disciplining Activity is not Phase Locking or Recovery Mode.
*Any Critical Alarms.
*Any Minor Alarms.
 
 
=Ubiquity ToS=
See https://help.ubnt.com/hc/en-us/articles/205231750-airMAX-How-is-QoS-and-prioritization-handled-by-airMAX-
 
 
So, if we set ToS/DSCP in the header to C0, then Ubiquity (and other gear watching ToS) ''should'' prioritize the packets. This sets the DSCP to 110 000 aka 48. UBNT shows this as 802.1p Class 6 (Voice <10mS latency). Other sources show this as a Network Control TOS.
 
 
There is an option in voter.conf to turn this on (utos=y). However, this only controls packets being sent from Asterisk '''TO''' the RTCM.
 
 
If you want to tag packets from the RTCM '''TO''' Asterisk, you need to set the RTCM debug option level to 16 (see [[#Debug Options]] for how this works).
 
 
At some point we should probably change the default behaviour of the RTCM firmware to mark the packets and use the debug setting to '''disable''' ToS. That change (if you wanted to compile your own firmware) would be:
 
<pre>
Change line 90 in IP.c
 
From:
#define IP_SERVICE        ((AppConfig.DebugLevel & 16) ? 0xc0 : (IP_SERVICE_ROUTINE | IP_SERVICE_N_DELAY))
 
To:
#define IP_SERVICE        ((AppConfig.DebugLevel & 16) ? (IP_SERVICE_ROUTINE | IP_SERVICE_N_DELAY) : 0xc0)
</pre>
</pre>




This changes the conditional expression from if the debug level is 16 to mark the packets with DSCP 48 to if the debug level is 16, mark the packets routine (DSCP 0).
=== JP1 - Discriminator Level Boost ===


Insert if low discriminator level. If squelch cannot self-calibrate with JP1 removed (too low), try with JP1 inserted.


=RTCM Simulcasting=
The RTCM/VOTER boards do support simulcasting, however, there are a bunch of quirks that one needs to be aware of.


'''Note:''' this jumper affects the squelch calibration circuit only. Not to be confused with JP2, which is the pad for the receive audio.


==Radio Hardware==
For best results, you should use all identical RF equipment between your voting RX sites and simulcast TX sites. If you don't, you can end up with strange audio artifacts when different receivers are used, and other strange audio issues when different transmitters are used. The most important thing when setting your levels is that ALL the RX and TX levels match from radio to radio. The best way this is achieved is using a "master" radio and reference from that - all radios might be identical models, but may not have identical audio characteristics so check those levels! Also check CTCSS and audio levels separately to make sure they all match.


=== JP2 - 20dB Pad ===


==9.6MHz Oscillator==
Insert to attenuate discriminator input level by 20db. This pad affects the '''receive audio level'''. See the [[#Receive Level Input Calibration | Receive Level Input Calibration]] section.
If you want reliable simulcast with an acceptable level of overlap warble, you MUST inject a GPS-disciplined or OXCO 9.6MHz signal to the clock of the RTCM's, in lieu of their stock internal crystal.  




Otherwise, the inherent internal clock jitter of the RTCM's will cause CTCSS warble, etc. in areas where your transmitters overlap. The 1 PPS feed that you normally feed the RTCM's is acceptable for voting, but naturally, a typical crystal-driven clock will slightly drift in between the pulses every second due to inherent jitter, etc., and that ain't to good for situations like simulcast which demand sample-accurate performance.
=== JP3 - Output Amp Power Source ===


Selects power source for output audio amplifier. 1-2 is to power it from the 5VDC power supply. 2-3 is to power it directly from Vin.


Here are some comments from Joe, KC2IRV, on the subject. He has also created his own wiki, specific to simulcast issues, you can find it at: http://rtcmsimulcast.wikifoundry.com/


:I felt I needed to let those on this mailing list know my findings with simulcasting with the RTCM units since I have received a great deal of help and information from people on this list.
=== JP4 - GPS TX RS-232/TTL Select ===


:For the past week I have had a two (2) site simulcast system up and running on UHF using the RTCM units. I have done a great deal of testing and proving on the bench and it is so far working beautifully.  
Selects GPS Serial transmit level. 1-2 RS232 Level, 2-3 TTL (5V) Level.


:The one issue that was made apparent to me early on was that in order for the RTCM's to be suitable for simulcast, the processor inside it needed to be clocked to a more accurate source. This source is supposed to be the Programmable Clock Generator Module in order to produce a GPS locked 9.6 MHz reference for the processor. Unfortunately this unit is not currently available.


:Knowing this, I started to go down the road of possibly designing my own, but stumbled upon a cheap, plentiful supply of Symmetricom 9.6 MHz sinewave OCXO's. I took a chance and ordered a few to experiment with to see if the RTCM would be able to use this in place of the supplied crystal for a clock. I found they did, with that I decided to modify the RTCM with an SMA connector just above the audio adjustment pots and use this OCXO. I trimmed the frequency on the units to match each other and used them to produce the processor clock.
=== JP5 - GPS RX RS-232/TTL Select ===


:After a week of testing, I have found the results in the overlap areas to be exactly as I would expect them on a public safety/commercial simulcast system. While in an overlap region where both transmitters are within 3dB of one another, to the ear you hear no audio phase wandering. Of course , this has only been a week of testing so I wouldn't call it case closed yet.
Selects GPS Serial receive level. 1-2 RS232 Level, 2-3 TTL (5V) Level.


:I will say that if this system remains this way after testing for 6 months to a year than using a 9.6 MHz OXCO is a viable alternative to achieve the needed precision and accuracy needed for the processor clock to make it suitable for simulcast.


=== JP6 – Not used ===


Comments from Jim Dixon on the issue:


:You have to use '''something''' that will take the precise 10MHz (or whatever it is) from the GPSDO and PLL (phase-locked) convert it to 9.6MHz (square wave at 3.3V for the CPU clock).
=== JP7 - Bootloader Programming ===


:We had to use 9.6MHz mainly because of the DAC in the dsPIC instead of 10MHz. The options for various divide/clock radios in the part are RATHER limited. As I recall, there wasn't even a way of getting the necessary 16kb/s sample rate on the ADC from 10MHZ, either.
This jumper only needs to be removed when programming the bootloader in the dsPIC using the ICSP header.  




=Micro-Node RTCM Clock Issue=
== Potentiometers ==
James, KI0KN, had some strange-ness with some of his RTCM's when used for voting. As soon as he changed menu item 10 on the RTCM to either a (1) or a (0) instead of (2), he '''instantly''' got this on the RTCM console:


<pre>
<pre>
04/05/2016 18:44:13.660  Lost GPS Time synchronization
R22 - Squelch adjustment
04/05/2016 18:44:13.660  Host Connection Lost (Pri) (10.16.1.240)
R36 - Rx Input Level
R10 - Tx Output Level
</pre>
</pre>




And it sits there forever and never re-establishes connection to the host. The issue was finally traced to a bad batch of 9.6MHz crystals that affected a small run of the RTCM's. The issue was eventually resolved by Micro-Node, but we'll document it here just for record keeping.
= Related Pages =
 
 
James comments to the list:
 
:Well, after many of you offered your time and thoughts on my voter problem, Jim, WB6NIL, graciously donated a couple of hours of his time to remotely help me and he uncovered the problem.
 
:All 5 of my RTCMs were purchased within the last 6 months, and I suspect all 5 have the same problem (will verify that today). The problem is that the microprocessor crystal is running too fast! There is 9.6Mhz crystal that drives the MPU, on the particular unit that Jim helped me diagnose, it's running 2.5 khz too fast. 
 
:There is a sanity check in the firmware that makes sure the correct number of samples were taken in the last second (it's supposed to be 8000) and fails if the sample is incorrectly sized (mine is taking 8003 samples).  Jim helped adjust the code to be more tolerant of the sampling error and my whole system instantly worked.
 
:I have since tested it with ALL my GPSs (they all work great!). So I now have everything working, including the voting.
 
:I haven't contact Micro-Node about it yet. Jim told me that voting should work fine but this clock error would probably not be acceptable for Simulcast (something we have no plans on doing as of now). Since mine are deployed at mountain top sites, I'll probably pursue a crystal that is running at the correct frequency and use "standard" firmware so that if the decision is ever made to play with simulcast, I won't be right back in this same boat.
 
:Thanks to all that helped out, and a HUGE thanks to Jim for taking the time to troubleshoot this.
 
:BTW- This clock error will NOT effect the RTCM in mix client mode, it only affects it in voting or simulcast mode!
 
:In voter.c, the stock line is:
<pre>
if ((samplecnt >= 7999) && (samplecnt <= 8001))
 
it needs to be changed to something like:
 
if ((samplecnt >= 7999) && (samplecnt <= 8003 ))
</pre>
 
:That was just enough to make my first RTCM work. I've had a chance now to check a few more of my RTCMs on the bench this morning and the crystal frequencies are kind of all over.  The next one I had on the bench was 5.2Khz fast. The above code was still not enough to fix it (as would be expected) so it looks like the quality control on whatever manufacturer that crystal is, isn't very good (or a low tolerance crystal is being used). I am going to pursue crystal replacement to get a highly accurate, stable, on-frequency crystal in there as my first choice. Changing the firmware 5 different times doesn't seem like the right answer.
 
:Jim put that sanity check in there for a reason. Working around it '''may''' allow the device to work, but to me, it seems getting the hardware operating the way it was supposed to originally is the better answer. I will follow up with Micro-node and let you all know how it goes.
 
 
After following up with Micro-Node:
:They were all off, some were off a LOT. I talked to Mark @ Micronode. He told me there were 25 units that made it out the door with a crystal from an unapproved source and that was quite likely the reason for the problem. He gladly sent me 5 new crystals to replace (he offered to replace them himself if I sent the units in, but I am comfortable doing it myself to save the time and postage).
 
:I haven't received them in the mail yet to show that the problem is fixed, but I will post here when that happens. He was great to work with and had no issue getting things set straight. If you are having the same issue and your RTCMs were bought about the same time, I'd suggest you contact him and have him help you resolve the issue!
 
 
=Duplex Mode 3=
Does delayed repeat audio bug you? Tired of hearing a bit of yourself after you unkey? Wish you could talk full duplex? Hate the echo chamber effect? Then we have the answer for you.
 
 
Duplex Mode 3 in app_rpt allows for "in-cabinet repeat" (where the radio hardware provides repeat audio) and app_rpt adds the hang time, courtesy tones, linking - all the
things apt_rpt does sans repeat audio. Therefore no repeat audio delay. Cool, eh? This duplex mode has been in app_rpt for a while. Problem has been how to implement it in the RTCM environment.
 
 
Duplex Mode 3 support in the RTCM provides in-cabinet repeat functionality. Repeat audio loops through the RTCM and has almost zero delay because it does not have to traverse the network. The delay is not quite zero but it's plenty short enough to eliminate all of the above mentioned annoyances.
 
 
Of course Duplex Mode 3 support can't be used with voting or simulcast. You also loose Touch Tone muting, Time Out Timer and Repeater Disable functions because the repeat path is not through app_rpt.
 
= Setting Voter Buffers =
Voter ping is useful for end-to-end network evaluation when ICMP ping is turned off and/or the RTCM is behind a firewall and is not ICMP reachable. It can also help with finding the correct RTCM and voter.conf buffer settings.
 
=== Voter Ping Usage ===
The voter ping asterisk CLI syntax is:
*CLI>voter ping nameOfClient [packetCount]
If packetCount is not specified 8 pings will be sent. Use packetCount of 0 to stop an in progress voter ping. Set packetCount to at least 100 when evaluating link quality.
 
The result will be similar to:
...
PING (nameOfClient): Packets tx: 100, rx: 100, oos: 0, Avg.: 26.710 ms
PING (nameOfClient):  Worst: 38 ms, Best: 22 ms, 100.0% Packets successfully received (0.0% loss)
The output above is self evident except for oos which is a count of out of sequence packets. Voter ping requires RTCM firmware 1.23 or newer and chan_voter 2013-08-04 or newer.
 
=== RX Buffer Size ===
Ping all the receiver sites and look for the worst response of the worst client. As a rough rule of thumb the buflen setting in voter.conf should be set to the worst response + 40ms or 120 whichever is greater. Using the above case the buflen should be set to 120 (38+40
 
=== TX Buffer Size ===
Ping all the transmitter sites and look for the worst response of the worst client. The RTCM TX Buffer Length should be set to (worst response + 40ms) * 8 or 480 whichever is greater. Using the above case the RTCM TX Buffer Length should be set to 624 ((38+40)*8).


=== Assumptions ===
Documentation on the VOTER/RTCM is extensive, and as such, has been split across multiple pages. They are usually linked, where appropriate, throughout the content. However, here are all the related pages that are available:
* The minimum TX buffer size is 480 (60ms) and the minimum RX buffer is 120ms. These were derived by testing on a LAN segment with chan_voter 2013-08-04 and RTCM 1.26.
* The ping times are not round trip times but they are in fact round trip times. Therefore the worst response could (should?) be divided by 2. Ie RX buffer = 38/2+40=59 and TX buffer = (38/2 + 40) * 8 = 472. Minimums still apply.
* The internet path to and from the RTCM under test is symmetrical.
* The added 40ms pad is an estimate of buffer ingress and egress.
As always your milage may vary. Some trial and error may be required to find the optimum settings.


=== Setup ===
*[[VOTER | Main VOTER Page]]
The RX buffer is set with buflen=120 in /etc/asterisk/voter.conf. The value is in milliseconds. The TX buffer is set in the RTCM with menu item 7. The value is in 125 microsecond increments. To match the size of the TX to the RX buffer, use the RX buffer * 8 to get the TX buffer size.
*[[VOTER-Hardware | Original VOTER Hardware Documentation]]
[[Category:How to]]
*[[VOTER-Menus | Menu Structure and Definitions]]
[[Category:Node Configuration]]
*[[RTCM_Firmware_upgrading | Firmware Upgrading]]
*[[VOTER-Audio | Audio Interfacing and Configuration]]
*[[VOTER-GPS | GPS Interfacing and Configuration]]
*[[Voter.conf | <code>voter.conf</code> Documentation]]
*[[RTCM_Channel_Driver | <code>chan/voter</code> and Asterisk Console Documentation]]
*[[VOTER-Simulcasting | Simulcasting Configuration]]
*[[VOTER-Buffers | Buffer Tuning]]
*[[Quantar_RTCM | Interfacing to the Motorola Quantar]]

Latest revision as of 18:08, 20 March 2022

Introduction

The Radio Thin Client Module (RTCM) is commercially available hardware for interfacing radios to an AllStarLink computer.

The Micro-Node RTCM (and VOTER) interfaces are typically used with AllStar in voting/simulcast applications. They MAY be used for ANY repeater interface application, through the chan_voter channel driver, as they are primarily a Radio over IP (ROIP) adapter.

The VOTER is the original through-hole board designed by Jim Dixon (SK) for this application. It is open-source, and the relevant Gerber files and BoM to build it are available.

The Micro-Node Radio Thin Client Module (RTCM) is the commercial version of the VOTER. It uses surface mount parts (SMT), but is functionally equivalent to the original VOTER. In general, the two terms (RTCM/VOTER) are used interchangeably, as they operate the same, and use the same firmware (mostly, see below).


Firmware

See the firmware upgrade page for information on upgrading the firmware.


Board Layout

Connectors and Switches

J1    - ICSP Programming Header
P1    - Radio
P2    - Console/GPS
SW1   - Reset (Momentary)
SW2-1 - Init EEPROM
SW2-2 - Calibrate Squelch
SW2-3 - Calibrate Diode
SW2-4 - RX Level LEDs


J1 - ICSP Programming Header (6 pin MTA-100)

1 - MCLR
2 - +3.3Vdc
3 - GND
4 - PGD (Program Data)
5 - PGC (Program Clock)
6 – NU


P1 - Radio Connector Pinout (DB9 Male)

1 - + VIn (7-24 Volts DC).
2 - Transmit Audio Out
3 - Receive (discriminator) Audio In
4 - External CTCSS Input (optional)
5 - Gnd
6 - Gnd
7 - /PTT Out (open-collector, active-low)
8 - Gnd
9 – Gnd


P2 - Console/GPS Connector Pinout (DB15 Female)

1 - NC
2 - Console Transmit Data
3 - Console Receive Data
4 - NC
5 - Gnd
6 - GPS Receive Data
7 - PTT Out
8 - Gnd
9 - NC
10 - Console Request To Send (RTS)
11 - Console Clear To Send (CTS)
12 - NC
13 - GPS Power Output (5Vdc @ 800ma MAX)
14 - GPS Transmit Data
15 – External Reset


SW1 - Reset

Depress SW1 momentarily to reset the RTCM.


SW2 - DIP Switch

SW2-1 - Init EEPROM
SW2-2 - Calibrate Squelch
SW2-3 - Calibrate Diode
SW2-4 - RX Level LEDs


SW2-1 "Initialize configuration parameters in EEPROM" (factory reset). If ON when firmware starts, the operating parameters in the EEPROM will be set to default values. The system activity LED (LD1, green) will stay off for aproximately 4 seconds, then stay on steady to indicate that the initialization process is complete. Afterwards, the switch may be TURNED OFF and the system will continue running normally. Note, if SW2-3 is ON during this procedure, the “Diode Calibration” process will also occur.


SW2-2 On to calibrate squelch. With the receiver connected and its antenna removed, switch on SW2-2. In the next few seconds the "Receive Signal Indicator" (LD3, Green) will flash on and off, then (hopefully) on steady. This indicates that the squelch calibration has occurred successfully. If unsuccessful, the LED will flash either fast to indicate that the discriminator noise level is too high, or slowly to indicate that the discriminator noise level is too low. Note, if SW2-3 is ON during this procedure, the "Diode Calibration" process will also occur.


SW2-3 On to perform "Diode Calibration". This may only be done in conjunction with a configuration parameter initialization (see SW2-1, above), or a "Squelch Calibration" (see SW2-2, above).


SW2-4 On to temporarily re-purpose LD4 and LD5 to allow for visual indication of RX input level. With SW2-4 on, LD5 will indicate (by brightness) if the RX level is too low, and LD4 will indicate (by brightness) if the RX level is too high. So the idea is to tune R36 so that there is minimal brightness on both LD4 and LD5 (like a null, more or less). Alternatively, Menu 97 on the console gives a more graphical method of setting the Rx input level.


LED Designations

LD1 - Heartbeat
LD2 - PTT
LD3 - COS On solid is valid Rx signal, flashing is without CTCSS
LD4 - GPS On solid is GPS received and locked, flashing is GPS received, lock in progress
LD5 - HOST


The COS (RX) LED on the RTCM will flash (same rate as Heartbeat LED) if you have External CTCSS enabled, and the received signal has the wrong (or no) valid PL.


Jumpers

JP1 - Discriminator Level Boost
JP2 - 20dB Pad
JP3 - Output Amp Power Source
JP4 - GPS TX RS-232/TTL Select
JP5 - GPS RX RS-232/TTL Select
JP6 - Not Used
JP7 - Bootloader Programming


JP1 - Discriminator Level Boost

Insert if low discriminator level. If squelch cannot self-calibrate with JP1 removed (too low), try with JP1 inserted.


Note: this jumper affects the squelch calibration circuit only. Not to be confused with JP2, which is the pad for the receive audio.


JP2 - 20dB Pad

Insert to attenuate discriminator input level by 20db. This pad affects the receive audio level. See the Receive Level Input Calibration section.


JP3 - Output Amp Power Source

Selects power source for output audio amplifier. 1-2 is to power it from the 5VDC power supply. 2-3 is to power it directly from Vin.


JP4 - GPS TX RS-232/TTL Select

Selects GPS Serial transmit level. 1-2 RS232 Level, 2-3 TTL (5V) Level.


JP5 - GPS RX RS-232/TTL Select

Selects GPS Serial receive level. 1-2 RS232 Level, 2-3 TTL (5V) Level.


JP6 – Not used

JP7 - Bootloader Programming

This jumper only needs to be removed when programming the bootloader in the dsPIC using the ICSP header.


Potentiometers

R22 - Squelch adjustment
R36 - Rx Input Level
R10 - Tx Output Level


Related Pages

Documentation on the VOTER/RTCM is extensive, and as such, has been split across multiple pages. They are usually linked, where appropriate, throughout the content. However, here are all the related pages that are available:

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