SPI Master pin set and clear

Question

I am trying to run the SPI code on an NRF52382 based custom board. I am using the NRF 52 DK, Keil uVision 5.0 , SDK 15.2. 
 
 I cannot set and clear the SPI relevant pins on my custom board as gpios. The pins I am using are: 
 SPI_SS_PIN = P0.6 SPI_MISO_PIN = P0.8 SPI_MOSI_PIN = P0.9 SPI_SCK_PIN = P0.7 
 and the schematic showing these pins is: 
 
 I was successfully able to toggle all four pins above, (as well as the RESET P0.21) as GPIOs after I did following: 
 1. went to sdk_config.h and changed NRF_LOG_BACKEND_UART_TX_PIN to pin 5 instead of 6 
 2. went to OPTIONS FOR TARGET -> C/C++ -> Preprocessor Symbols -> Define and added " CONFIG_NFCT_PINS_AS_GPIOS" after nrf52382.... and removed the line " CONFIG_GPIO_AS_PINRESET" 
 
 But as soon as I run the SPI example code in SDK15 I am unable to toggle these pins and use them as gpios. Especially the SPI_SS_PIN which is pin 6, as soon as I run the SPI code this pin fixes to high value and will not clear/go low. 
 My thinking is there something wrong with the way the SPI example configures the spi relevant pins? 
 https://devzone.nordicsemi.com/f/nordic-q-a/18546/gpio-not-set-or-clear-with-spi-code this guy seemed to have had the same problem running SPI and with the CS pin... 
 Thank you!

hmolesworth · Accepted Answer

Any of the pins you mention should work, there is no preferred pin. If you have a fatal error it is probably from app_error_fault_handler() which can be the default handler in app_error_weak.c or a handler of the same name you have supplied. In either case put a breakpoint on the first code line of that handler and enable Stack Trace in the IDE debugger so you can see where the error came from. You can do that in any of the usual IDEs (IAR, SES, Keil ..) and see the sucessive code lines which caused the error; Then place a breakpoint on any of the suspect lines and restart-execute again to see what data was causing the error. 
 I see you have analogue inputs; if the SAADC is enabled I suggest commenting out that code in case one of those pins is also set as an adc function. With no pins showing up in a search (try search " 6") it is possible that there is some board hardware issue. A return to the bare-bones example with only the pin 6 changed might be the next step if any of the above doesn't help ..

SPI Master pin set and clear

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