Programming HID Bootloader on PIC32

• Create a new project (I called it Bootloader) in the Bootloader folder. Click Next

Please include the following C files in the project. These files should already exist within the Bootloader folder:

1. HardwareProfile.h (a universal header file for various boards)
2. HardwareProfile_NU32.h (hardware configuration specific to NU32; if you have a custom hardware profile, it should be appended to the general HardwareProfile.h)
3. main.c (the primary source file)
4. main.h
5. procdefs.ld (a linker file)
6. usb_config.h (header file for configuring USB communication)
7. usb_descriptors.c (source file for USB communication)

Please proceed by clicking “Next.”

• Click Finish

Creating Bootloader Hex File

Upon completing the setup, MPLAB should display the following interface. The project window showcases all the files you’ve integrated into the project. Specifically, the ‘procdefs.ld’ file can be found within the linker file folder. It’s important to note that this file isn’t the sole linker file, so you should relocate it by dragging it into the ‘Other Files’ folder.

The purpose of the ‘procdefs.ld’ file is to instruct the programmer or bootloader on where to place files. It’s crucial to have a distinct ‘procdefs’ file for the bootloader and the files you intend to load with the bootloader. This separation ensures that new programs are stored in a different location than the bootloader on the PIC. If you mistakenly use the same ‘procdefs’ file as the one used for the bootloader, the bootloader will attempt to overwrite itself, effectively erasing it and failing to install the new program. In such a scenario, you’ll need to re-install the bootloader on the PIC.

To set up MPLAB to locate the header files from the Microchip Applications Library, follow these steps:

1. Navigate to Project>Build Options>Project in MPLAB.
2. Within the “Directories” tab, select “Include Search Path” from the dropdown menu.
3. Add a new path by browsing to the location of the “include” folder (e.g., C:\Microchip Solutions\Microchip\Include).
4. Add another new path by browsing to the folder where your project is located.
5. Click the “OK” button to confirm and save your changes.

As the bootloader relies on the USB source files from the Microchip Framework, we need to incorporate these source files and specific USB header files into the project. I’ve organized these files into sub-folders in the project window as outlined below.

1. Within the project window, right-click on ‘Source Files’ and select ‘Create Subfolder.’ I’ve named this new folder ‘USB Framework.’
2. Right-click on the newly created folder and choose ‘Add Files.’ Incorporate the following files:
– usb_device.c from … -> Microchip Solutions -> Microchip -> USB
– usb_function_hid.c from … -> Microchip Solutions -> Microchip -> USB -> HID Device Driver
3. In the project window, right-click on ‘Header Files’ and select ‘Create Subfolder.’ Name this folder ‘USB Framework.’
4. Right-click on the newly created folder and choose ‘Add Files.’ Integrate the following files from … -> Microchip Solutions -> Microchip -> Include -> USB:
– usb.h
– usb_ch9.h
– usb_common.h
– usb_device.h
– usb_function_hid.h
– usb_hal.h
– usb_hal_pic32.h

Since we’re using a generic HardwareProfile, it’s important to specify the board to MPLAB. Essentially, we are providing MPLAB with a constant that indicates the board to use.

1. Navigate to Project -> Build Options -> Project and click on the MPLAB PIC32 C Compiler Tab.
2. Currently, the preprocessor macros window is empty. We need to create a variable defined for our board. Click ‘Add’ and enter ‘PIC32_NU32’ if you’re working with the Northwestern PIC32 board.
3. Click ‘OK.’
4. Click ‘OK’ again.

To minimize the size of the Bootloader Hex file and ensure it occupies minimal space on the PIC, it’s important to optimize the compiler for the smallest code size. Failure to do so may result in the bootloader not functioning properly.

1. Navigate to Project -> Build Options and click on the MPLAB PIC32 C Compiler Tab as previously.
2. Click on the ‘Optimization’ category.
3. Select the ‘s’ option for the smallest size, as depicted below. If this option is unavailable, choose the smallest code size available.