1.34 SPI Self Loopback DMA

This example demonstrates transmit and receive operation over SPI interface using DMA. Two DMA channels are used - one for transmission and another for reception. The loop back test requires the MOSI output pin to be connected to the MISO input pin so that anything transmitted will also be received. The example first transmits 10 bytes and receives 10 bytes. If the received data is same as transmitted then it transmits 0 bytes and receives 10 bytes. In this case, dummy data will be transmitted to receive 10 characters, hence all the received data should be 0xFF. Next, 10 bytes are transmitted and 5 bytes are received. Here, the received bytes must match the first 5 bytes in the transmit buffer. Finally, 5 bytes are transmitted and 10 bytes are received. In this case, the first 5 bytes in the receive buffer must match the first 5 bytes in the transmit buffer. The remaining 5 bytes in the receive buffer must be 0xFF.

To clone or download this application from Github, go to the main page of this repository and then click Clone button to clone this repository or download as zip file. This content can also be downloaded using content manager by following these instructions.

Path of the application within the repository is apps/spi/master/spi_self_loopback_dma/firmware.

To build the application, refer to the following table and open the project using its IDE.

To load the application binary onto the target device, we need to use at91bootstrap loader. Refer to the at91bootstrap loader documentation for details on how to configure, build and run bootstrap loader project and use it to bootstrap the application binaries.

The following table shows the target hardware for the application projects.

1. Build the application using its IDE
2. LED indicates the success or failure:
   • The LED is turned ON when the received data matches the transmitted data