- It is a technique of burning the code into the microcontroller in the absence of an external programmer.
- Entight connection from board to pc via USB.
- One microcontroller(PIC) already programmed with a bootloader.
- For the bootloader to operate properly we need to access boot mode.
- Don’t let go the reset button until the activation of boot mode when the USB cable is attached to the port.
- Note that the required driver installation will fail due to the absence of the drivers by default, therefore we have to install them manually.
- UPDATE UNKNOWN DEVICE DRIVERS
- From the given popup window select browse for drivers
Enter the path to where the corresponding drivers can be found in directory path and after that click install.
- Now we can view the microchip device from the device manager settings under all settings tab.
- Writing code for a bootloader is quite analogous to what we used to perform in cases except for some slight variations.
- The main difference comes where the user program starts from the address 0x800.
- Therefore the address of the reset vector should be at 0x800.
- Normally , reset is in position 0x00 and the interrupt vectors are in 0x08 and 0x18, therefore they have to be remapped.
- You have to set the code offset as 0x800 for the project to be compiled.
- For that that, project properties ->xc8 linker.
- Then from the Options Categories menu, click on Additional options.
- Finally add 800 corresponding to the displayed code offset box.
BURNING NEW PROGRAMS USING BOOTLOADER:
- Initially Boot into bootloader mode by pressing the reset key without leaving it via connecting the USB cable until boot menu shows up.
- Next click on the PDFUSB.exe file from the Pdfusb folder.
- Afterwards select PICUSB 0 as the boot device.
- Finally dump the hex file via button.
- Suppose the loaded code starts from a random memory than 0x800, you will need to put an extra line to your created hex file.
- Observe that the text circled in red is 4262E20, which points to the starting address.
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