FW: TNC-Pi


Tommy Kane
 

Is there a problem with the system, replies not showing up.

 

Tommy

MM0KNE

 

From: Tommy Kane [mailto:coolcamper55@...]
Sent: 02 April 2014 14:28
To: 'Raspberry_Pi_4-Ham_RADIO@...'
Subject: RE: [Raspberry_Pi_4-Ham_RADIO] TNC-Pi

 

Update to status.

 

Checked out the connectivity to U4) all fine and 3.3v on the appropriate pin. Unable to hear a tone using earphones, loaded Visual Analyser and spent quite a time trying to understand that. Help pages were rather vague, found a forum that talked about it so read most of the pertinent info and tried again.

When attaching a probe to pin3 in the 4 pin header  area or to pin 6 on the IC, I notice a change in the display of VA. Unfortunately it dies after 3 seconds so difficult to evaluate. Not sure if its the IC dying or something in VA. I am finding VA setup is as user friendly as a cornered rat.

I also need to understand how I can change the OP of the IC incase its too low.

Any experts on VA who can help with the 3 second issue would be appreciated.

 

Tommy

MM0KNE

 

From: Raspberry_Pi_4-Ham_RADIO@... [mailto:Raspberry_Pi_4-Ham_RADIO@...] On Behalf Of John Hansen
Sent: 31 March 2014 21:53
To: raspberry_pi_4-ham_radio
Subject: Re: [Raspberry_Pi_4-Ham_RADIO] TNC-Pi

 

 

You should see the yellow LED flash every now and then; that is normal.  The fact that the yellow LED doesn't come on solidly when packet data is received means that for some reason the audio is not getting to the modem chip (or the modem chip is not working or the connection between the modem chip and the PIC is not there).  I would use an earphone (or even better an oscilloscope if you've got one) to look for audio on pin 6 of U4.  If you don't hear anything there, it will simplify your debugging job because it probably means either the cabling of the radio to the TNC isn't right or the level is too low. 

John Hansen
Coastal ChipWorks

 

On Mon, Mar 31, 2014 at 3:31 PM, <coolcamper55@...> wrote:

 

Folks, Bit of help required here.

I have recently received the TNC-Pi and built it but having a bit of a struggle to get it working.

I installed all the Wheezy files and AX25 as per the instructions from K4gbb' site (that is when I could get in, seems to have been dropping lately), I also downloaded xastir and set it up killing the kissattach prior to setting it up.

In the ax25 set up it offers the Calibrate function where it sends a string of 1's and 0's until the buffer is empty.

I monitor that on another HT but all I get is white noise, no distinct tone.

I also attached a speaker to the TNC-Pi board and again no distinct tone just the white noise.

When I first sitch the Pi on, both red and yellow lights come on then red goes followed by yellow. As far as I know this is standard. Every now and then the DCD or Yellow light will blink but when there is a full blown APRS transmission there is no visible signs on the TNC-Pi that it has heard anything. I am using a Quasheng TG-UV2 HT and the cable specs are as per those in the Byonics site but not really sure if its the TNC-Pi or the TNC -HT cables.

Any assistance in helping me track down or narrow down the field of enquiry would be much appreciated.

 

Tommy

MM0KNE

 


Tommy Kane
 

Further update, have buzzed out all connections from Modem IC and PIC IC  plus most of the board and all shown fine. I tried again with the Visual ANalyser software and have come to the conclusion that all I am getting from the probe points is mains hum.

I get a very low throbbing but definitely not a clear audible tone.


Seriously running out of ideas, maybe time to dust off the tiny Track4

Tommy

MM0KNE


John G8BPQ
 

Tommy,

 

If you like I’ll take a look at it. I’m going to be away for most of April but could check it out when I get back.

 

73,

John G8BPQ

 


From: Raspberry_Pi_4-Ham_RADIO@... [mailto:Raspberry_Pi_4-Ham_RADIO@...] On Behalf Of coolcamper55@...
Sent: 04 April 2014 08:42
To: Raspberry_Pi_4-Ham_RADIO@...
Subject: Re: FW: [Raspberry_Pi_4-Ham_RADIO] TNC-Pi

 

 

Further update, have buzzed out all connections from Modem IC and PIC IC  plus most of the board and all shown fine. I tried again with the Visual ANalyser software and have come to the conclusion that all I am getting from the probe points is mains hum.

I get a very low throbbing but definitely not a clear audible tone.

 

Seriously running out of ideas, maybe time to dust off the tiny Track4

Tommy

MM0KNE


Ian <jedscoot@...>
 

Tommy,

I had a " dead " TNC-PI with no tx audio. My fault was a bad solder joint on the 26 pin connector.

Just a stab in the dark !!!

73,
Ian..
--------------------------------------------

On Fri, 4/4/14, coolcamper55@... <coolcamper55@...> wrote:

Subject: Re: FW: [Raspberry_Pi_4-Ham_RADIO] TNC-Pi
To: Raspberry_Pi_4-Ham_RADIO@...
Date: Friday, 4 April, 2014, 8:41


 









Further update, have buzzed out all
connections from Modem IC and PIC IC  plus most of the
board and all shown fine. I tried again with the Visual
ANalyser software and have come to the conclusion that all I
am getting from the probe points is mains hum.I get a
very low throbbing but definitely not a clear audible
tone.
Seriously running out of
ideas, maybe time to dust off the tiny
Track4TommyMM0KNE










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Tommy Kane
 

Well any stab in dark is worth it, however after refloating the solder on the 26pins no change. I have found that if I probe the TX audio point, it dies after 2-3 seconds (same response on pin6 U4), maybe a capacitor or something breaking down but I am beat for the moment.

 

 

Thanks for the help so far.

 

Tommy

MM0KNE

 

From: Raspberry_Pi_4-Ham_RADIO@... [mailto:Raspberry_Pi_4-Ham_RADIO@...] On Behalf Of Ian
Sent: 04 April 2014 12:05
To: Raspberry_Pi_4-Ham_RADIO@...
Subject: Re: FW: [Raspberry_Pi_4-Ham_RADIO] TNC-Pi

 

 

Tommy,

I had a " dead " TNC-PI with no tx audio. My fault was a bad solder joint on the 26 pin connector.

Just a stab in the dark !!!

73,
Ian..
--------------------------------------------
On Fri, 4/4/14, coolcamper55@... wrote:

Subject: Re: FW: [Raspberry_Pi_4-Ham_RADIO] TNC-Pi
To: Raspberry_Pi_4-Ham_RADIO@...
Date: Friday, 4 April, 2014, 8:41


 









Further update, have buzzed out all
connections from Modem IC and PIC IC  plus most of the
board and all shown fine. I tried again with the Visual
ANalyser software and have come to the conclusion that all I
am getting from the probe points is mains hum.I get a
very low throbbing but definitely not a clear audible
tone.
Seriously running out of
ideas, maybe time to dust off the tiny
Track4TommyMM0KNE










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Tommy Kane
 

John, Very kind offer, what I think I will do is persevere until you have more time and if it's still a problem, let you have a go at it. Again much appreciated

 

Tommy

MM0KNE

From: Raspberry_Pi_4-Ham_RADIO@... [mailto:Raspberry_Pi_4-Ham_RADIO@...] On Behalf Of John Wiseman
Sent: 04 April 2014 09:25
To: Raspberry_Pi_4-Ham_RADIO@...
Subject: RE: FW: [Raspberry_Pi_4-Ham_RADIO] TNC-Pi

 

 

Tommy,

 

If you like I’ll take a look at it. I’m going to be away for most of April but could check it out when I get back.

 

73,

John G8BPQ

 


From: Raspberry_Pi_4-Ham_RADIO@... [mailto:Raspberry_Pi_4-Ham_RADIO@...] On Behalf Of coolcamper55@...
Sent: 04 April 2014 08:42
To: Raspberry_Pi_4-Ham_RADIO@...
Subject: Re: FW: [Raspberry_Pi_4-Ham_RADIO] TNC-Pi

 

 

Further update, have buzzed out all connections from Modem IC and PIC IC  plus most of the board and all shown fine. I tried again with the Visual ANalyser software and have come to the conclusion that all I am getting from the probe points is mains hum.

I get a very low throbbing but definitely not a clear audible tone.

 

Seriously running out of ideas, maybe time to dust off the tiny Track4

Tommy

MM0KNE


John
 

I'm not clear as to whether you are working on receive audio or transmit audio here.  If it's receive audio, I suggested looking on pin 6 of the MCP6023 because after it runs through resistor R3, I find it is somewhat difficult to detect.  On receive, you should see audio at pin 6 (if you don't, take a close look at the connecting cable from your radio and the connections in the area of U4 and focus on this until you find where the audio gets lost).  If you do find audio there, take a look at the pattern of data coming out of pin 13 of the MX614.  You should always see a data pattern there, but when packets are being received, you should see a noticeable change in this pattern.

If you working on transmit audio, the first thing to check is whether bits are actually getting to the PIC from the Pi.  Look for data pulses on pin 8 of the PIC when you are attempting to send data from the Pi.  If you don't see anything there, the problem is either with the Pi configuration or with the data path from the Pi to the TNC (make sure the jumpers are both on!).  If you do see data there, then check the Red LED to make sure it lights up when transmitting.  If you see data on pin 8, but don't get a a red LED, then contact me and I'll send you a replacement PIC (though there is possibility of a bad modem chip as well... this is unlikely if receive is working).

John W2FS


On Fri, Apr 4, 2014 at 4:25 AM, John Wiseman <john.wiseman@...> wrote:
 

Tommy,

 

If you like I’ll take a look at it. I’m going to be away for most of April but could check it out when I get back.

 

73,

John G8BPQ

 


From: Raspberry_Pi_4-Ham_RADIO@... [mailto:Raspberry_Pi_4-Ham_RADIO@...] On Behalf Of coolcamper55@...
Sent: 04 April 2014 08:42
To: Raspberry_Pi_4-Ham_RADIO@...


Subject: Re: FW: [Raspberry_Pi_4-Ham_RADIO] TNC-Pi

 

 

Further update, have buzzed out all connections from Modem IC and PIC IC  plus most of the board and all shown fine. I tried again with the Visual ANalyser software and have come to the conclusion that all I am getting from the probe points is mains hum.

I get a very low throbbing but definitely not a clear audible tone.

 

Seriously running out of ideas, maybe time to dust off the tiny Track4

Tommy

MM0KNE



Tommy Kane
 

Today I double checked and buzzed out the PCB all connections are showing OK.

I had previously checked out the transmit by starting xastir and when "transmit now" was actioned the radio did indeed transmit however it did not sound like aprs to me but first I started on the RX.  

The radio has the ability to receive local FM broadcast stations so I tuned into one of them. APRS traffic in the area is rather sparse and the fm station gave me the ability to obtain a steady input and to confirm that the receive cable was correct.

With the PI / TNC powered off, I was able to detect the audio on most of the points that the circuit diagram suggested.

This included pins on the Op amp, PIC various resistors and capacitors eg C8.

I also got clear audio going into R3 but as suggested not able to pick it up on the downside.

On the Modem chip the following was found

Clear audio on Pin 6

No audio on Pin 5

Audio heard on Pin 13 but badly distorted.

I powered up the Pi and started to look at the TX side.

Pulse detected on Pin8 of PIC

I then opened Xastir and started the TNC, it came up and I pressed the Transmit Now option. The Radio did transmit and it was heard by another radio. Checked APRS.fi and found that the nearest digi had picked it up and had passed it onto APRS.fi.

 

As I mentioned earlier, APRS is a tad sparse around here and the nearest digi beacons every 30 minutes  and I have managed to receive and decode the output 3 times.

It seems to be working although I am not sure about the distortion across the modem chip, and I still have not heard the 450Hz tone that is supposed to be there all the time.

 

 

As to the fix, might have been a dry joint somewhere, I had to re-sweat a couple of contacts to get a meter reading. I will leave it running for 24 Hrs and see what it looks like.

This TNC plus the Pi are destined for remote deployment in SAR work so need to be sure, we do have backup systems but this is ideal in terms of storage and power options.

You can probably see the APRS.fi data for yourself.

The additional bonus of all this effort is that I am getting a lot of use with the Oscilloscope software.

 

Many thanks for all the advice and offers of assistance, it really is appreciated.

 

Tommy

MM0KNE

 

 

From: Raspberry_Pi_4-Ham_RADIO@... [mailto:Raspberry_Pi_4-Ham_RADIO@...] On Behalf Of John Hansen
Sent: 04 April 2014 15:11
To: Raspberry_Pi_4-Ham_RADIO@...
Subject: Re: FW: [Raspberry_Pi_4-Ham_RADIO] TNC-Pi

 

 

I'm not clear as to whether you are working on receive audio or transmit audio here.  If it's receive audio, I suggested looking on pin 6 of the MCP6023 because after it runs through resistor R3, I find it is somewhat difficult to detect.  On receive, you should see audio at pin 6 (if you don't, take a close look at the connecting cable from your radio and the connections in the area of U4 and focus on this until you find where the audio gets lost).  If you do find audio there, take a look at the pattern of data coming out of pin 13 of the MX614.  You should always see a data pattern there, but when packets are being received, you should see a noticeable change in this pattern.

If you working on transmit audio, the first thing to check is whether bits are actually getting to the PIC from the Pi.  Look for data pulses on pin 8 of the PIC when you are attempting to send data from the Pi.  If you don't see anything there, the problem is either with the Pi configuration or with the data path from the Pi to the TNC (make sure the jumpers are both on!).  If you do see data there, then check the Red LED to make sure it lights up when transmitting.  If you see data on pin 8, but don't get a a red LED, then contact me and I'll send you a replacement PIC (though there is possibility of a bad modem chip as well... this is unlikely if receive is working).

John W2FS

 

On Fri, Apr 4, 2014 at 4:25 AM, John Wiseman <john.wiseman@...> wrote:

 

Tommy,

 

If you like I’ll take a look at it. I’m going to be away for most of April but could check it out when I get back.

 

73,

John G8BPQ

 


From: Raspberry_Pi_4-Ham_RADIO@... [mailto:Raspberry_Pi_4-Ham_RADIO@...] On Behalf Of coolcamper55@...
Sent: 04 April 2014 08:42
To: Raspberry_Pi_4-Ham_RADIO@...


Subject: Re: FW: [Raspberry_Pi_4-Ham_RADIO] TNC-Pi

 

 

Further update, have buzzed out all connections from Modem IC and PIC IC  plus most of the board and all shown fine. I tried again with the Visual ANalyser software and have come to the conclusion that all I am getting from the probe points is mains hum.

I get a very low throbbing but definitely not a clear audible tone.

 

Seriously running out of ideas, maybe time to dust off the tiny Track4

Tommy

MM0KNE