40 pin header

[GaryLa]

Hello,

I assume this is up-to-date: ROCK64_Schematic_v2.0_20170704.pdf

Is it true that the following "dedicated signals" could be re-purposed as regular IO as they only go the 40-pin header?

CLK32KOUT_M1
UART2_TX
UART2_RX


Also, why does SPI_CSN0_M2 appear on this header? It is dedicated as a chip select on SPI flash IC U1 (the GD25Q128CS).

Any use of this pin as either SPI or GPIO will cause U1 to drive the MISO pin (pin 21 on the 40 pin header).

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.

[GaryLa]

Isn't there at least one employee who monitors this forum?

Someone knows the answers to my question -- but, WHO ??

[zehks]

Im sorry for not answering your question and throwing another,

is the 40-pin header (pi2 bus) available to use with a raspberry shield? such a PXFmini

[GaryLa]

Im sorry for not answering your question and throwing another,

is the 40-pin header (pi2 bus) available to use with a raspberry shield? such a PXFmini

That is pretty much the same question I'm asking. The Raspberry Pi has multi-use pins on its header just as the Rock64, but apparently you CAN re-purpose them.

I'm supposing the Rock64's can be too. I don't need the UART or the CLKOUT, but I do need them as GPIO pins. From their schematic, they appear to only go to the header, therefore it should be entirely possible to just reprogram them as GPIOs.

Can you configure pins 4, 14, 15, and 18 to be normal GPIO on the Pi ?
Or are they required to be CLKOUT, TX, RX, and PWM ?

[xalius]

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...

[GaryLa]

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.