Jump to main content

# 1.9 FLEXCOM SPI Self Loopback DMA

This example application shows how to use the FLEXCOM SPI peripheral with DMA to transmit and receive a block of data.

## Description

This example demonstrates transmit and receive operation over FLEXCOM 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 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, therefore 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.

## Downloading and Building the Application

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 be downloaded using content manager by following these instructions.

Path of the application within the repository is apps/flexcom/flexcom_spi_self_loopback_dma/firmware.

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

Project Name | Description
--- | ---
sam_9x75_curiosity.X | MPLABX project for SAM9X75 Curiosity Development Board
sam_9x75_curiosity_pro.X | MPLABX project for SAM9X75 Curiosity Pro Development Board

## Setting Up AT91Bootstrap Loader

To load the application binary onto the target device, the user needs 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.

## Setting Up the Hardware

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

Project Name | Description
--- | ---
sam_9x75_curiosity.X | SAM9X75 Curiosity Development Board
sam_9x75_curiosity_pro.X | SAM9X75 Curiosity Pro Development Board

### Setting Up SAM9X75 Curiosity Development Board

- Use jumper wire to connect MOSI of mikroBUS connector to MISO of mikroBUS connector:
  - FLEXCOM5 MOSI signal is mapped to PA16 that is routed to Pin 6 of mikroBUS connector
  - FLEXCOM5 MISO signal is mapped to PA15 that is routed to Pin 5 of mikroBUS connector
- Connect the UART DEBUG J35 on board to the computer using a UART-FTDI cable (to enable debug com port)
- Connect the USB port J2 on board to the computer using a micro USB cable (to power the board)

### Setting Up SAM9X75 Curiosity Pro Development Board

- Use jumper wire to connect MOSI of mikroBUS connector to MISO of mikroBUS connector:
  - FLEXCOM3 MOSI signal is mapped to PC22 that is routed to Pin 6 of mikroBUS connector
  - FLEXCOM3 MISO signal is mapped to PC23 that is routed to Pin 5 of mikroBUS connector
- Connect the UART DEBUG J63 on board to the computer using a UART-FTDI cable (to enable debug com port)
- Connect the port J1 on board to the computer using a Type-C USB cable (to power the board)

## Running the Application

1. Build and run 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

Refer to the following table for LED name:

Board | LED Name
--- | ---
SAM9X75 Curiosity Development Board | RGB_LED (Green)
SAM9X75 Curiosity Pro Development Board | RGB_LED (Green)

Rev: E