Digirig lite 1.1 won't PTT

I have a digirig lite rev 1.1 which doesn’t want to drive the PTT. Running on a Raspberry Pi. I can use cm108 to test the gpio line and I see the line go high and low coming out of the CM108 chip. But I don’t see anything on the connector to the cable. I am suspecting a blown transistor but I’m not sure. I can’t seem to find the 1.1 version of the schematics. I see the 1.2 version but it looks a lot different than the 1.1 rev.

Can anyone offer some guidance or point me to the schematic?



I have the 1.0 version of Lite and I notice that it does not reliably trigger PTT on certain radios. If I swap in my home-brew version of the DigiRig lite, it does work as does a Masters Communication DRA-50 (which also uses GPIO PTT). In my case, I think the resistor driving the transistor that controls PTT was too high in the original version. I used a 10K resistor on my home brew card and it works fine. It seems to be radio-dependent, though. DR Lite 1.0 works great on a Kenwood TM-D710G or BTech HT (Linux or Mac or Windows PC), but not on an Anytone AT-D578.

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Rev 1.0 had too high of the resistor value in series to the PTT line. This was done to eliminate the resistor needed in some HT cables that share mic and PTT line (e.g. Yaesu HT cable below), but caused issues with some other models:

You can try shorting the resistor out to see if this solves the issue you are experiencing:


In later revisions the resistor was lowered to 100 ohms for only current limiting purposes.

Here’s the schematic for rev 1.0
digirig-light.pdf (117.7 KB)

On my Icom there was just no PTT. But on a Yeasu FT-65 or a Tidradio TD-H3 it was actually crashing direwolf. I’m not sure if there was an issue with the CM108 crashing or what. I’ll go ahead and swap that resistor for a 100Ohm one. Thanks for the picture and the schematics. Should help a lot.

By the way, I really like the form factor for the 1.1 rev. It is pretty convenient for home-brew projects. I’m trying to make a Pi TNC and put it in a small box, so the small form factor and lack of cables is actually a plus.



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That seems to have fixed my issues. It is now working on my IC-2100 after I swapped the resistor for a 100Ohm one. Thanks for your help.


Awesome! Thanks for reporting your success.

73 Constrainted