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FreeRTOS 18F452 Port

Posted by Debraj Deb on March 4, 2008

I was trying out the port for 18F452 (MPLAB).

The code building works fine and the entire code fits in the Flash memory. I get the following info in "map" file: -
Program Memory Usage
Start End
--------- ---------
0x000000 0x000005
0x000008 0x000025
0x00003a 0x0043be
17321 out of 33048 program addresses used, program memory utilization is 52%

But my final application is on 18F4520 (successor to 18F452). Hence I changed the device and linker script to 18F4520. But then, I get the following linker error: -
MPLINK 4.15, Linker
Copyright (c) 2007 Microchip Technology Inc.
Error - section '.udata_heap_1.o' can not fit the section. Section '.udata_heap_1.o' length=0x00000404
Errors : 1

I think, the error means that the code for "heap_1.c" is too big to be fitted in the memory. Why is this error? I know that the memory of 18F4520 >= memory of 18F452.

I also noticed that even if I revert the device and linker script back to 18F452 (same as original), the same linker error appears. Why is that?

Best regards.

RE: FreeRTOS 18F452 Port

Posted by PICmeup on March 4, 2008
The freertos heap in heap_1.c is defined as one big array so is to big to fit in a small memory block as defined in the MPLAB linker scripts. Look at the 18f452.lkr file in the pic18_mplab folder to see a mod to create one large bit of RAM called BIG_BLOCK. This is the 18f452.lkr file in the pic18_mplab folder of freertos not the file in the mplab folder.

RE: FreeRTOS 18F452 Port

Posted by Debraj Deb on March 4, 2008
Thanks. This information helps me immensely.

Best regards.

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