How many max SPI slave sensor I can connect with Nrf52840 via SPIM

[Chitrang Talaviya]

Hello Folks,

I am using PCA 10056 Eval board. I am using SPIM0 to connect 5 slave sensors. The Chip select is done by the UART Tx pin. So If I send 0x01 over UARt then the sensor- 1 will be selected.

UART Tx byte -- Sensor 0x01 -- 1 0x02 -- 2 etc

Sensors are LSM6DSL

I have five sensors connected via SPIM0 to nordic nrf52840. I am only able to get the reading from 1 or 2 sensors only which is connected closely to nordic. Is there any max limit with the current SPIM hardware and software limitations in terms of max slaves?

ALso, How to change the CS duration and RX delay timing of the SPIM hardware using the SDK 14?

Thank you

[Dave_couling]

Ok, well there is no official UART Tx pin. GPIOs can be assigned as you see fit. I wouldn't use the UART driver to set your CS pins. This will create issues with your UART and SPI Driver code. When you initialize your SPI module you need to specify a CS pin. If you wish to talk to multiple devices the best way is to uninit and re-init the SPI module with whatever CS pin you wish to talk to. The SPI driver code in nrf_drv_spi.c will handle the CS pin selection.