SPI issue on nRF52

[Tosa]

I'm using nRF52+SDK11.0.0+S132 with an application based on the ble_hrs example.

In main(), if I call a blocking nrf_drv_spi_transfer() to configure some SPI sensors before calling ble_advertising_start(), then my code spins in spi_xfer()'s while (!nrf_spi_event_check(p_spi, NRF_SPI_EVENT_READY)) {}. If I swap the two calls, the SPI function does not spin. What is the issue?

[Tosa]

It turns out that I was assigning P0.21 for SCK, which caused reset on the nRF52 DK (I'm using the DK for code development before porting to custom hardware). So the following pins are fixed when using the nRF52 DK: // PCA10040 fixed pins: 32kHz 0, 1; UART: 5, 6, 7, 8; NFC 9, 10; BTN: 13, 14, 15, 16; LED: 17, 18, 19, 20; RESET: 21