Raspberry pi 4 (4GB model)
4.5 inch touch screen (attached via GPIO, video coming from a small HDMI to micro HDMI jumper)
Macchina M2 (interface board and stock m2 cpu board)
Now, pin 16 coming from an OBD2 port is 12v, the macchina can handle it. The macchina also has a 5v output.
My Pi 4 requires 5v to run, and from what I have been reading, the pins for power and ground (4 and 6, respectively. Please correct me if I am wrong.) are connected to the same rail as the USB-C port it uses for power.
It stands to reason that I can power the Pi 4 via the 5v output on the macchina, which itself is powered by by the 12v power coming from the OBD2 port. I know it can work like this, and the 5v coming out of the Macchina is stable (well, as long as the car battery itself is), and has failsafes.
If I am wrong in the above conclusion, please correct me...
That being said, I also have a touchscreen sitting on the GPIO drawing power, but also taking up the pins I would use to pass the 5v power from the obd2 port to the macchina m2. Now, if I say tap the 5v pin and power the pie from the 5v output and leave it that way, I should be able to power up the device with no issues, correct? Essentially both the macchina m2 and Pi 4 with the screen will go in the same case (work in progress), so I will likely tap the underside of the one of the boards or make a reaallllly short header to go between the Pi 4 GPIO and the touchscreen's connection to the gpio, so that the Maccina, when it's plugged in to a car, will power the pi and screen, but still leave the stock power usb-c connection functional for power when I have it sitting on the bench and am developing/testing with it.
Lol. I know it sounds convoluted, but is my thinking above correct? I cannot find anything that says it will not work, and the numbers seem to match. Just don't want to fry the thing my first time hooking it up. It really shouldn't though, if those GPIO pins are on the same path as the usb-c power.... humor me.
Thanks for your help in advance.