So, I have a serial device that I can talk to, but not from.

I can connect at various bauds and send commands, which are executed, but I don't get any information back, not even echo.

What stupidly obvious thing have I forgotten / got wrong?

This device used to work, as did the serial->usb. Plus known good adaptors have same issue.


@M0YNG Perhaps check with a scope that the microcontroller of that device is actually sending and the level shifter circuit is working. Or perhaps you can do some sort of loopback tests at various locations inside the circuit to encircle the defect. and be sure there is no stupid misconfiguration :)

· · SubwayTooter · 2 · 0 · 0

@M0YNG ok, perhaps high-impedance headphones will do the job as the waveform of the signal is not important but just whether there is something moving at the tx pin. rs232 should be in the audible spectrum at lower baud rates. with a bit of luck even a multimeter (AC-setting) might work

@dk7lst @M0YNG A logic probe (especially one with audio output) will tell you at least if the RS-232 pins are wiggling. I'm wondering about a fried transmit driver.

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