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# 1.2.1 SAM D21 Xplained Pro Evaluation Kit: Building and Running the SPI EEPROM Bootloader applications

## 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 repo or download as zip file. This content can also be download using content manager by following these instructions

Path of the application within the repository is apps/spi_eeprom_bootloader/

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

## Bootloader Application

Project Name | Description
--- | ---
bootloader/firmware/sam_d21_xpro.X | MPLABX Project for SAM D21 Xplained Pro Evaluation Kit

## Programmer application

Project Name | Description
--- | ---
app_programmer/firmware/sam_d21_xpro.X | MPLABX Project for SAM D21 Xplained Pro Evaluation Kit

## Setting up SAM D21 Xplained Pro Evaluation Kit

- To run the demo, the following additional hardware are required:

  - One EEPROM 4 click board

  - One mikroBUS Xplained Pro board

- Install the EEPROM 4 click board on to the mikroBUS Xplained Pro board

- Connect mikroBUS Xplained Pro board to the EXT2 header

- Connect the Debug USB port on the board to the computer using a micro USB cable

## Setting up the host script

- Refer to UART Host Script Help for setting up the uart_host.py utility used to send the application binary from host PC

  - There will be no reset command sent from host after programming by default.

  - Reboot command has to be sent separately only after successful programming to trigger bootloader from programmer application

## Running the Application

1. Open the bootloader project bootloader/firmware/sam_d21_xpro.X in the IDE

2. Make sure that the app_programmer/firmware/sam_d21_xpro.X is added as a loadable project to bootloader application

   - As the SPI EEPROM may not have any valid binary required by bootloader for the first time, Adding the app_programmer as loadable allows MPLAB X to create a unified hex file and program both these applications in their respective memory locations based on their linker script configurations

3. Build and program the bootloader application using the IDE

4. Once programming is done bootloader starts execution and directly jumps to application space to run the programmer application

   - LED0 starts blinking every 500ms indicating that the programmer application is running

5. Open the programmer application project app_programmer/firmware/sam_d21_xpro.X in the IDE

6. Update app_programmer/firmware/src/app.c to reduce the LED blink duration from 500ms to 100ms as below

       	APP_TIMER_DelayMs(100);

7. Clean and Build the project to generate the binary (Do not program the binary)

8. Run the uart_host.py from command prompt to program the updated programmer application binary in SPI EEPROM

        python <harmony3_path>/bootloader_apps_serial_memory/tools/uart_host.py -v -i <COM PORT> -d samd2x -a 0x2000 -f <harmony3_path>/bootloader_apps_serial_memory/apps/spi_eeprom_bootloader/app_programmer/firmware/sam_d21_xpro.X/dist/sam_d21_xpro/production/sam_d21_xpro.X.production.bin

9. Following snapshot shows output of successfully programming the programmer application

   - LED0 should still be blinking every 500ms

10. Run the uart_host.py from command prompt to send a Reboot command. This command Updates MetaData and triggers Bootloader to program the updated binary from SPI EEPROM to Internal Flash

        python <harmony3_path>/bootloader_apps_serial_memory/tools/uart_host.py -v -i <COM PORT> -r

11. Once Firmware Update is successful LED0 should start blinking every 100ms indicating updated programmer application running

    - If there was any error you may need to power cycle the device to retry firmware upgrade

12. Update app_programmer/firmware/src/app.c to revert LED blink duration to 500ms from 100ms as below

        APP_TIMER_DelayMs(500);

13. Clean and Build the project to generate the binary (Do not program the binary)

14. Repeat Step 8-9.

    - You should see LED0 still blinking every 100ms

15. Press the Switch SW0 to Update MetaData and trigger Bootloader to program the updated binary from SPI EEPROM to Internal Flash

16. Once Firmware Update is successful LED0 should start blinking every 500ms indicating updated programmer application running

    - If there was any error you may need to power cycle the device to retry firmware upgrade

## Additional Steps (Optional)

- To bootload any other application refer to Application Configurations

  - Note that this application should have programming capabilities to SPI EEPROM

- Once done repeat the applicable steps mentioned in Running The Application