Quick Arduino question before I blow my radio

Hi!

I’m trying to control the PTT on my radio with an Arduino. It works, but when the Arduino is unplugged it defaults to PTT on, and I don’t want to damage my radio and break laws for transmitting an empty carrier.

The PTT line is connected to pin 2. It reads 5 volts(Pullup in the radio). The radio GND is connected to the Arduino GND. To enable PTT, I have to pull pin 2 low. The problem is the Arduino defaults to it being low when off.

My solution is as follows: Tie the PTT line to VCC. Tie the GND line of the radio to pin 2. When pin 2 reads low, PTT should be off(5v to PTT, 0v to GND). When pin 2 reads high, PTT should be on(5v to PTT, 5v to GND, but because it’s all relative that should be the same as PTT to GND)

It’s important for me to note that VCC is not tied to the radio in any way, as far as I can tell. The only way would have to be through the PC USB VCC line to the audio line back to the radio somehow.

submitted by /u/laptopdude90
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