An issue in NRF51822 custom board as spi slave with BLE

RE: An issue in NRF51822 custom board as spi slave with BLE

aalsubhi — Thu, 02 Jul 2020 14:08:44 GMT

Thanks, Turbo for your help. It turned out to be a power issue with My PCB.

RE: An issue in NRF51822 custom board as spi slave with BLE

Turbo J — Sun, 21 Jun 2020 06:36:57 GMT

Irrelevant: SPIS does not rely on pin changing interrupts - it uses the CS signal directly in hardware.

The only effect here would be a delay between end-of-transaction and the actual SPIS interrupt handler being executed.

At this point I recommend cutting the CS wire/trace and putting a series resistor (100R - 1k) in. This lets you measure which chip powers the line with a multimeter. Oscilloscope would be nice, too...

RE: An issue in NRF51822 custom board as spi slave with BLE

aalsubhi — Sat, 20 Jun 2020 22:26:32 GMT

I found this in the SDK v10 documentation about GPIOs which might explain why CS pin never goes low:

Working with a SoftDevice

When a SoftDevice is enabled, it can interrupt the application at any time for a certain amount of time. This can lead to the situation where some pin level changes are missed. If the application must track an input pin that can change its level frequently, PPI should be used with a high-accuracy event together with a TIMER in counter mode to count the detected transitions.

Any idea/example of how to do what is suggested?

RE: An issue in NRF51822 custom board as spi slave with BLE

aalsubhi — Sat, 20 Jun 2020 20:34:29 GMT

Also, I used the SEGGER RTT library to print out the error code for "nrf_drv_spis_init" and it was returning 0 which means the spis initiated successfully.

RE: An issue in NRF51822 custom board as spi slave with BLE

aalsubhi — Sat, 20 Jun 2020 16:54:56 GMT

I'm not using uart at all in my code or including any uart driver/ code. Also, I tested the connectivity of the CS pin by using the continuity test on a multimeter. I placed one prob on NRF51822 CS pin and the other prob on MSP40 (master) pin where is NRF51822 CS is connected. The connection is fine.

RE: An issue in NRF51822 custom board as spi slave with BLE

Turbo J — Sat, 20 Jun 2020 14:59:01 GMT

[quote userid="91350" url="~/f/nordic-q-a/62835/an-issue-in-nrf51822-custom-board-as-spi-slave-with-ble"]hen I connected the NRF51822 custom board, the CS never goes low ( it always high even when the Master drives it low to start the spi communication ). [/quote]

That could only happen if it is either not properly connected or the pin is configured elsewhere as an output (e.g. for UART).

If two outputs fight each other, the resulting voltage is usually somewhere "in the middle" - but if the pin is in high drive mode there might be a chance it overwhelms the MSP IO pin.