Here’s an example radio’s (FT-7900) pin connection via the mini DIN 6 connector on the rear of
the radio:
Pin number
Signal name
Wire color
Mini DIN 6 connector
3
RX audio
White
9600 from radio
4
Signal ground
Yellow
GND
6
TX audio
Green
Audio to radio
7
PTT
Blue
PTT
Adjusting signal levels (hardware)
Here is a picture of the test points on the PCB that can be used to look at the RX and TX signal
levels on an oscilloscope. The signal on JP7 is the RX signal audio on the ADC input pin of the
STM32 chip. JP6 has the TX signal audio on the pin going to the radio.
