Sharing GPIO between I2C and SPI ?

RE: Sharing GPIO between I2C and SPI ?

Jørgen Holmefjord — Wed, 21 Apr 2021 08:25:49 GMT

Yes, you can use these pins, and they are not limited to "Low frequency IO only". I was confused by your last comment where you said you wanted to use SD card (SPI) and LCD (I2C) on the same pins, but if both are running over SPI there should be no problems.

RE: Sharing GPIO between I2C and SPI ?

RixtronixLAB — Tue, 20 Apr 2021 20:54:14 GMT

Hi Jorgen,

My question is ,

Is it possible that I use these GPIO for SPI ?

P0.20 = MOSI

P0.21=MISO

P0.22=SCK

I want to use SD card and LCD on the same SPI port only with different CS pin,

Thanks

RE: Sharing GPIO between I2C and SPI ?

Jørgen Holmefjord — Tue, 20 Apr 2021 14:26:28 GMT

Hi,

Not sure if I understand your question. You cannot change the HW traces on the PCB from software, but you can configure which internal peripheral in the nRF52840 that is connected to receive or output data to the traces.

I do not know if the devices you connect will work correctly if you output both SPI and I2C data to the same pins, without some kind of switch to disconnect the device(s) that uses another protocol. For instance, if you use the same pin for SPI and I2C clock and runs SPI at 8 MHz, this is way outside the maximum clock frequency supported by most I2C devices, and may cause damage or issues with the I2C device.

Best regards,
Jørgen

RE: Sharing GPIO between I2C and SPI ?

RixtronixLAB — Tue, 20 Apr 2021 00:37:20 GMT

For example I use in PCB :

P0.20 = MOSI

P0.21=MISO

P0.22=SCK

they're configureable via software ?

Thanks

RE: Sharing GPIO between I2C and SPI ?

RixtronixLAB — Mon, 19 Apr 2021 22:43:39 GMT

Hi Jorgen,

Thanks for the reply,

Any examples for doing on the PCB, I want to use SPI for SDcard and I2C for LCD

Thanks

RE: Sharing GPIO between I2C and SPI ?

Jørgen Holmefjord — Mon, 19 Apr 2021 09:28:27 GMT

Hi,

Any GPIO can be assigned to any serial peripheral in all the nRF5x series ICs, thanks to the pin crossbar feature. Just disable one peripheral using the pins before assigning the pins to another peripheral. You cannot configure two different peripherals to control the same GPIOs at the same time.

Note that the defines in the board header files are used for different examples, and may not all be intended for use by one example. These pins often chosen from convenience by the software developer, and may not be optimal from a HW perspective or for your application. E.g, make sure that you follow the guidelines with regards to "Standard drive, low frequency I/O only" markings in Pin assignments documentation.

Best regards,
Jørgen