No need to “steal”, you can just “use" it.:) Yes, one MCU’s outputs can certainly be another MCU’s input. No resistor or pull up or down is needed, the output is driven high or low. Any MCU’s input is going to be high impedance and will have no perceptible effect on the driving device.
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if all the second device needs is T/R switching then, yes, just tap off that signal. if you need more information (SSB/CW, band, other) then I2C might be the way to go.
On Oct 25, 2019, at 12:50 PM, Rob French (KC4UPR) <email@example.com> wrote:
Question--I'd like to use the T/R signal from the Raduino on pin 16 (or pin 1, depending on which diagram), which drives Q15 to switch the T/R relay, to synchronize with another microcontroller. Can I simply tap (with a suitable 1K resistor, probably) from the Raduino T/R pin over to the other microcontroller? It will be an INPUT pin (I haven't checked yet to see whether it should be pullup or pulldown), so my understanding is the impedance should be very high from the Raduino's perspective. But, obviously I don't want to mess up my T/R switching!
Alternatively, I could use an I2C signal from the Raduino to the other device. Perhaps that's a better idea? (It will be receiving I2C inputs regardless.) The other device is doing both transmit and receive audio DSP, so I want to make sure it gets switched around as required.