So, I got a Raspberry Pi 4 Model B, and I'm trying to make a project using relay boards. Turns out, when I turn on my Pi, one of the pins is already active and the indicator turned on partially. I took a tester and kept on the GPIO pins just to find that they were active without any script activating them. Is my Pi defected or is it a built-in feature to keep the GPIOs on?
Please let me know. Thanks!
All the GPIO are pulled high or low at power-up. GPIO 0-8 are pulled high to 3V3 the rest low to ground.
The pulls are quite weak (about 50k). If you need a different default you need to add external pulls.
See page 102 of datasheet for the default pulls.
See pinout for the mapping of pins to GPIO.
This has NOTHING to do with the Pi or GPIO.
These lousy modules are unsuitable for use with the Pi (they are poor for Arduino).
They can only be turned off by putting 5V on the inputs (or by setting GPIO to INPUT)!
Using with the PI risks damage!
NOTE there are hundreds of similar Questions by others who have problems with these.
See Can you use a 5V Relay Module with the Pi?
PS the module DOES NOT indicate the state of the Pi GPIO. To reliably check see GPIOreadall
