RE: UART printf stops in spi_event_handler function

Vala — Thu, 29 Sep 2016 09:43:43 GMT

Thanks for your answer Aryan.

RE: UART printf stops in spi_event_handler function

Susheel Nuguru — Tue, 20 Sep 2016 11:22:43 GMT

Printf uses UART and depending on what drivers you are using it can be blocking or non blocking. In SDK6, using simple_uart.c API in retarget.c made printf blocking because then UART did not use any interrupts and waited until it sends/receives a byte.

But at later SDKs UART drivers and libraries became asynchronous using their interrupt handlers.

Since you are using SDK11 so you are using app_uart with fifo. Then the UART irq priority will be defined in the nrf_drv_config.h file

#define UART0_CONFIG_IRQ_PRIORITY APP_IRQ_PRIORITY_LOW

If SPI drivers are using APP_IRQ_PRIORITY_HIGH then you will be able to write to fifo but the actual write to uart will be delayed as data is written synchronously byte by byte through the ISR.