As title said, the GPIO behave other then the GPIOs of a raspberry Pi here.I suppose this is caused by the built-in pull-up/-down resisotrs.
I would like to access these GPIOs through carrierboard’s 40-pol pinheader (J30)
Pin “MCLK05” (“gpio422”,pin number 7 of Expansion Header) is one of my choice used as input. through file system interface (/sys/class/gpio/gpio422/export) I can export this pin dynamically, change its direction and read its value without issue. But later I figured out it’s not as easy as a proper configured GPIO of a Raspberry pi to pull-down.
In one of my test, I’m using a external 1K Ohm pull-down resistor for this gpio,and its still too big for its purpose (875 Ohm works).
Later I discovered, with a MCU controlled MOSFET, I can not bring this pin to 3.3V (3.3V is selected through J514),but with the same setup I can toggle a GPIO from a pi.
I’m pretty sure there is no damage of the Xavier Devkit from very beginning. (ESD protected, J514 selected properly, Working voltage for GPIOs never go over 3.3V).So I would like to deactivate the built-in resistor firstly.
There are two possible ways to achive this:
Edit Xavier’s dtb file or edit memory block directely. I prefer the later one. But its still not clear how to calculate the memory address for this gpio, and what kind of value should I set.Counld someone give me some advice?