[since "ASF" is now "Atmel Software Framework" - not just AVR]
D21 ASF Manual: http://www.atmel.com/Images/Atme...
The one and only mention of master_slave_select_enable is in Table 14-3 - and all that tells you is that it's a bool, and the description is just "Enable Master Slave Select"
There is no explanation nor illustration of how to actually use that option!
None of the examples uses it.
If I take the SAMD21 Xplained-Pro SPI_QUICK_START_MASTER_CALLBACK example and add the following:
config_spi_master.pinmux_pad1 = EXT1_SPI_SERCOM_PINMUX_PAD1; config_spi_master.master_slave_select_enable = true;
the result is a mess - see the attached scope traces (showing SCK and SS).
The version with master_slave_select_enable set actually takes longer - and gets split up into individual bytes!
Anyone got this actually working :?: