Using bootloaders

[kgng97ccs]

I am using the PIC18LF46K22 MCU, MPLAB IDE v8.92, and CCS C compiler v5.113.

I am new to bootloaders, and I am trying to understand what a bootloader can do in comparison with what I can do in MPLAB IDE v8.92.

Now, I understand that if wish to be able to program the MCU in a finished product without opening the casing to access the programming connector on the PCBA, I can use a bootloader to do the programming through a serial port (a hardware or software UART).

I have tried the option of generating bootloader code using the project wizard in the CCS IDE.

Questions:

1. With MPLAB IDE (v8.92), I can compile a program, set the EEPROM table, and then load the hex file and EEPROM data (or an MCH file) into the MCU memory.

Question:
As there are normally two files that need to be programmed into the MCU – the hex file and MCH file, does a bootloader work in such a way that we have to load one file after the other, or is it that we have to combine both into one single hex file first and then load the combined file?

2. With MPLAB IDE, I can also read the MCU memory and export the hex file, with or without the EEPROM data embedded, and export (save) the EEPROM data into an MCH file.

Question:
Can a bootloader be set to do the same thing, that is, read back the contents of the MCU memory and then export them?

3. With MPLAB IDE, I can set the programmer (PICKit3, for example) to erase all memory before programming a hex file and an MCH file into the MCU, to replace the existing hex file and EEPROM data on the MCU.

Question:
Can a bootloader be set to do the same thing, that is, erase all memory before starting the programming?

I will appreciate any comment or advice. Thank you.

[temtronic]

While I do use the 46k22, I've never used a bootloader with it. I dedicate the ICSP pins for exclusive ICSP use. To access ICSP and RS232, I'd use a DE-9 connector (5 or ICSP, 4 for RS-232).

A bootloader cannot 'erase all memory' then load the application program, otherwise it'd erase itself. That section of memory has to be protected.

Bootloaders have only been 'one way'..send data TO the PIC, not read data out of the PIC and send to the 'host' (PC). You can edit a bootloader to add this function though I suspect it'd be easier to simply edit the main() program to do this 'remote read'.

I don't know what an 'MCH' file is. A PIC with a bootloader has 2 programs. 1) the actual bootloader program, small and protected and then the application program what is normally called 'main()'.

CCS provides working bootloader programs, in the examples and drivers folders.

[Ttelmah]

The only file loaded into a PIC, is the hex file (or the same data as a .bin
file). The compiler does not generate a MCH file and one is not needed.
The only time I have met a MCH file is when using a Model Checking
program as a way of testing the code operation. There are a few other
things that use this file extension (there was an audio format that used
this), but none that I can think of that have anything to do with
programming a PIC....
MCH was used for exporting part of an EEPROM on the Old Pickit
software, but is not supported on the current releases. I think it was
a text format giving the location and data. Now standard Intel Hex
is used instead. The current versions of the MicroChip software no
longer support this format.

If you have an MCH file and want to store this, you would have to write
your own code to do this. It is not a format that would be recognised
by any standard PIC program and most definitely not by a bootloader.

Understand that a bootloader only writes code to the processor memory.
In the PIC, the internal EEPROM is mapped into the standard processor
memory map so this can be written by a bootloader.

However, if you want to modify one to write to an external EEPROM, I
would advise against this. It is always worth keeping the bootloader as
small as possible, and adding such an ability would be bulky. Much better
to add this as an ability to the main code in the processor, where it
can be maintained and updated by the bootloader.

[asmallri]

[asmallri]