Bootloaded application does not run, how to trace the error?

ferrumvir · Joined: 01 Feb 2006 Posts: 64 Location: England

Hi,

I've written a bootloader which does everything I think it should, however all applications I've attempted to load with it fail to run.

I wrote a lot of details into another thread http://www.ccsinfo.com/forum/viewtopic.php?t=29529 but no one seemed prepared to read through it, fair enough it is rather a long post.!. Sorry for starting a new thread, but hopefully this is a more readable/answerable post.

Can anyone give me any advice on how to trace the error and solve the problem?

Thanks Scott

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

One way to find the problem would be to:

1. Write a very small application program. By small, I mean two lines
of code in main(). Use as little of the CCS library code as possible.
Library code is invoked with #use() statements.
Confirm that the application program runs OK if you use a normal
programmer to burn it into the PIC (ie, don't bootload it).

2. Now download it to the PIC, using the bootloader.

3. Confirm that it fails.

4. Read the PIC's program memory using your programmer and MPLAB.

5. Look at the Program Memory window in MPLAB. Print out the listing.

6. Study the listing. Look for where the error occurs. It may be jumping
to an address where it expects a library routine to be, but in fact there's
nothing there. It may using a RAM location that is also being used
by another part of the program, and thus it's being corrupted.

7. Print the .LST file for the application program (the non-bootloaded
listing, that's made by MPLAB when you compile the application).
Compare that listing with the one that you read from the bootloaded
code. Look for any important differences between the two listings,
with respect to program flow (jumps) and RAM usage.

-------
With regard to people not looking at your post:
Remember who you're asking questions to -- most of us are working
at jobs during the day where we're supposed to get something done.
If I see a post with tons and tons of code in it and I'm supposed to be
drawing a schematic, I just say "I don't have time for this", and I skip
the thread. That's why I always say to people "Keep it short". The
shorter the post (or the code), the better the chance that we will have
the time to look at it. I think other people feel the same way.

ferrumvir · Joined: 01 Feb 2006 Posts: 64 Location: England

Thanks PCM Programmer,

Only needed to get as far as Point 4. Thanks for that, it had not crossed my mind to do that...

Found the bug and it was as small one (but as usual - critical), and now the application works just fine.

The problem I had, should you wish to know, was a check when to erase_program_eeprom