Sorry if this is a weird setup to troubleshoot, but I'm mystified about what's going on here in my project involving multiple RPis.
I have two RPi 4 systems running identical client programs. The python code checks several pins for their HIGH or LOW states, collect them in a string and send them to a server program running on a laptop. The intent is to use the 3.3V pin on one Pi to set the listening pins on the other Pi to HIGH.
When I have the Pis connected to monitors via the HDMI ports, the program works fine. Pi #1's 3.3V pin will set Pi #2's GPIO pin to HIGH, and vice versa.
When I disconnect the HDMI cable to Pi #1, it will no longer set any of the GPIO pins of Pi #2 to HIGH. It happens as soon as the monitor is disconnected.
What I've observed:
-Pi #1's 3.3V will still set Pi #1's GPIO pins to HIGH, regardless of the monitor being connected or not.
-I used a multimeter to confirm that I am still getting a 3.3V from the headless Pi.
-If I apply a separate 3.3V battery source to Pi #2's GPIO pins, they will be set to HIGH.
-I had thought this headless issue was due to running pygame in the code that I was using for a testing interface (I already had a headless flag to disable any windows being drawn when not testing), but I've commented out all of that code, to no avail.
-I connected an LED in line with the connector from #1's 3.3V to the #2 GPIO pin, and it illuminates, so the voltage is being sent.
Is there some hardware safety feature somewhere I'm unaware of that's stopping this process when headless? Or is this a python problem?
Model (for both): Raspberry Pi 4 Model B Rev 1.2
I have two RPi 4 systems running identical client programs. The python code checks several pins for their HIGH or LOW states, collect them in a string and send them to a server program running on a laptop. The intent is to use the 3.3V pin on one Pi to set the listening pins on the other Pi to HIGH.
When I have the Pis connected to monitors via the HDMI ports, the program works fine. Pi #1's 3.3V pin will set Pi #2's GPIO pin to HIGH, and vice versa.
When I disconnect the HDMI cable to Pi #1, it will no longer set any of the GPIO pins of Pi #2 to HIGH. It happens as soon as the monitor is disconnected.
What I've observed:
-Pi #1's 3.3V will still set Pi #1's GPIO pins to HIGH, regardless of the monitor being connected or not.
-I used a multimeter to confirm that I am still getting a 3.3V from the headless Pi.
-If I apply a separate 3.3V battery source to Pi #2's GPIO pins, they will be set to HIGH.
-I had thought this headless issue was due to running pygame in the code that I was using for a testing interface (I already had a headless flag to disable any windows being drawn when not testing), but I've commented out all of that code, to no avail.
-I connected an LED in line with the connector from #1's 3.3V to the #2 GPIO pin, and it illuminates, so the voltage is being sent.
Is there some hardware safety feature somewhere I'm unaware of that's stopping this process when headless? Or is this a python problem?
Model (for both): Raspberry Pi 4 Model B Rev 1.2
Statistics: Posted by GogglesGreek — Mon Jun 10, 2024 6:40 pm — Replies 1 — Views 96