CTL_STATUS_t ctl_spi_get(CTL_SPI_DEVICE_t *self);
ctl_spi_get reads a single frame from the SPI device self which must have been previously selected onto the bus by ctl_spi_select_device. The idle value set in the device's protocol is written to the SPI bus when exchanging data with the device.
The value returned is the frame read from the SPI bus; negative values are standard status codes.