Help Needed with Bootloader to External memory!

nmeyer · Joined: 09 Jul 2004 Posts: 70

I have been trying unscucessfully to modify the ccs bootloader to use it to switch over between internal and external flash memory on the 18F8722. I have another post that has some of my code
http://www.ccsinfo.com/forum/viewtopic.php?t=37313
and i have been trying several things to get it to work and i am running out of ideas. I am not sure at this time if this will even work. Does anyone have experience using external memory on any chip? Also, using the bootloader to load this memory? What i have makes sense, but it just will not bootload. Any suggestions will be greatly appreciated.

FvM · Joined: 27 Aug 2008 Posts: 2337 Location: Germany

You have been posting rather complex code in the previous thread. It may be the case, that no one is motivated to work his way through. Furthermore, without having the chip and an external memory connected to it, he's unable to check the code in real life. Bad prerequisites for getting effective help I fear.

Generally, when implementing some special code of this kind and failing at first (or second) attempt, I would not expect to get a ready made answer from the forum. Not without some more visible effort of my own. You unlike others have the code and the hardware at your fingertips. You gonna consider some means to check your applications operation in detail by tracing it with a debugger. Possibly, an assembly level debugger as MPLAB with ICD-2 may be helpful.

P.S.: I took a brief look at the at29c1024 driver and didn't see, that it involves necessary programming action of flash memory at all. Did you verify if and in which part of the code the flash programming is performed? I'm missing e.g. the characteristic unlock codes. Maybe I simply overlocked it, but it could also be, that the driver is somewhat incomplete... At least it's unwise to repeat a check for succesful programming endlessly with no timeout.

nmeyer · Joined: 09 Jul 2004 Posts: 70

Thanks for you comments. I know the code in the previous post is long, but i could not fully display the issue by make some short program and posting it. I have been working this same issue since November on proto boards and then with my real hardware. I have no issues with hardware, that all checks out. I can not tell you how many iterations of code i have been through in the last two months. As I stated earlier I have exhausted all ideas i can think of and my coworkers also have no new ideas. I am not asking for the solution from anyone, i just hope that some one might give a suggestion that will make me take a look at this in a different way. I'll keep plugging away and hopefully i will have a break through. Thanks

FvM · Joined: 27 Aug 2008 Posts: 2337 Location: Germany

I think, the PIC18F8622 support status is as follows (please correct me, if I'm wrong):

- #org statements for external program memory (above address 0x20000) are presently no accepted by CCS C

- the at29c1024.c example doesn't contain any flash programming code. It's not more than a template, where the // TO DO comments have been forgotten.

While the latter issue can be solved by coding your own flash routines, I don't see an easy way to allocate program code to the external flash due to the first one.

Best regards,
Frank