01-07-2018, 11:58 AM
(This post was last modified: 01-07-2018, 12:02 PM by GaryLa.
Edit Reason: added question
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(01-07-2018, 06:57 AM)xalius Wrote: Yes sure, as long as the pin also has GPIOx_ name in the schematic, you can disable the special function via the devicetree and use them as GPIO. You also have to disable the device node of the block using the pins in some cases, like UART2 here...
Thanks for the response. I know that is generally true, but in the case of GPIO3_B0 (SPI_CSN0_M2) -- this pin is connected to the chip select of U1 on the Rock64.
Even if you repurpose it, it will still drive the chip select -- it's the same wire. Therefore, when used as a GPIO and driven low, U1 will start driving SPI's MISO line. This will collide with anything that is using SPI at the moment.
Also, the graphic that shows the 40-pin header (ROCK64_Pi-2 _and_Pi_P5+_Bus.pdf) states the the SDMMC0_xxxx pins can be used as GPIO as long as no MicroSD is used.
How do these pins operate during boot? If they are intended to be used as GPIO by an application, the boot process may inadvertently cause a daughterboard to react because the application hasn't booted yet.
Any guidance would be appreciated.