LP-AM243: SDK的例程mcspi_loopback_dma_am243x-lp_r5fss0-0_nortos_ti-arm-clang是SPI Master的，修改成SPI Slave用的过程中有问题。

做slave时，需要注意下面的guideline。

• The MIBSPI protocol does not account for a built-in handshaking mechanism and neither does this driver. Therefore, when operating in SLAVE mode, the application must provide such a mechanism to ensure that the MIBSPI slave is ready for the MIBSPI master. The MIBSPI slave must call MIBSPI_transfer() before the master starts transmitting. Some example application mechanisms could include:
  • Timed delays on the MIBSPI master to guarantee the MIBSPI slave is ready for a MIBSPI transaction.
  • A form of GPIO flow control from the slave to the MIBSPI master to notify the master when ready.

https://software-dl.ti.com/mcu-plus-sdk/esd/AM273X/08_01_01_06/exports/docs/api_guide_am273x/DRIVERS_MIBSPI_PAGE.html

我使用的时候已经注意到了这一点，在SPI Master开始传输之前，SPI从设备先调用了 MCSPI_transfer()，然后等待SPI Master传输数据，但是SPI从一直没收到SPI Master过来的数据，所以程序始终是在等待信号量的状态，但是我连上逻辑分析仪可以看到SPI Master是发出数据了的。

请问SPI slave模式下，发送可以吗？还是只是不能接收？

发送和接收都不可以