Problems with using 2 spi slaves (sdcard and one more spice device)

[IlyaM]

Hi,

I wanna use nrf51822 as master which has 2 slaves:  sdcard (fatfs) and adc

I set SPI_INSTANCE 0

and they don't want to work together, I mean I'd like to write some data to sd card and after that call ADC.

sd_write();

callADC();

but if I comment out one of them (sdcard or ADC) it works fine only if I use SPI_INSTANCE 1 of ADC

But I want to use shared clock, most and miso

also I tried to set each CS to HIGH before calling

What I do wrong?

ps: from these topics I found out that nrf51 can't switch chip selects

https://devzone.nordicsemi.com/f/nordic-q-a/23432/interfacing-two-slaves-on-spi-master

https://devzone.nordicsemi.com/f/nordic-q-a/23488/a-nrf52-function-mapping-to-nrf51

And some alternative solutions, but nothing instead of using different pins for spins instance helped

But still, is it possible to use 1 master and 2 more slaves (where one of them is SDC) with shared SPI lines (of course instead of CS) with chip select switch???

[Jørgen Holmefjord]

Hi,

Are you using the SD Card and FatFS libraries from the SDK? Note that the SDK libraries does not have support for sharing the SPI instace between multiple devices, but you could change the library to expose the instance and use the same one for your ADC slave device.

Also note that CS is normally active-low, meaning you should set it low for the device you are interfacing, not high.

Best regards,
Jørgen