Here is my setup:
I have a raspberry pi zero w —> digirig —> Yaesu FTM-400
It all works perfectly, except when the power is removed from the raspberry pi, the PTT will enable and stay enabled on the FTM-400. To resolve the problem, it requires repowering the raspberry pi or disconnecting the audio cable from the digirig.
This does not happen with the Kenwood TM-V71A.
Not a huge issue.
That happened to me with a windows laptop, on a local repeater, where a digital communication meeting was about to begin so there were many listeners. It does not always happen, but when it does, you remember. Now it is just second nature for me to unconnect only from the audio side and not the USB side. I think K0TX is working on it.
Thanks for the info. I will start probing around with the scope and see what I can find. If I discover anything, I will share my results.