I've been suprised by the dearth of examples for programming Microchip PIC® processors in SDCC, given there's been continuous effort in improving it's support since about 2001 or so. As such, I am placing the things I've managed to create or find, here.

I originally started with the PIC16f628a, which is a nice and versatile 14-bit embedded processor with a lot of built-in goodies. If you haven't already, I strongly suggest you check out my PIC16f628a page first.

Recently I've started experimenting with the PIC18f2550 processor, which is very different for a number of reasons:

• At least eight configuration registers. Eight! I spent a lot of time banging my head on the wall looking for a combination of options that didn't just sit there like a lemon.
• USB support. Something I haven't explored yet. Please don't ask me how it works yet, I have no clue!
• An internal oscillator that runs at a variety of configurable frequencies from 8Mhz on down.
• A cthulian dual-oscillator phase-locked-loop setup necessary for USB support, which partly explains the explosion in number and complexity of configuration registers.
• A more-powerful 16-bit instruction set, more code memory, and more RAM.
• A built-in A/D converter with multiplexed inputs.
• More pins in general. 28!
• A more complex bootloader scheme. So far I'm quite happy to let SDCC handle that for me.
• Tons more things I have yet to realize.

But it still shares the following abilities:

• It works reliably with my JDM-style programmer, even under Linux®. I've been unable to find any consistent source for the programmer but it's available all over the place and looks exactly like this. The JDM is an open design anyway -- buy it or build your own, the PIC doesn't care. :) Of course you'll have a hard time finding all the fiddly zeners and transistors so personally I think you're better off buying the whole programmer -- it's got a nice ZIF socket, and comes with useful Windows softare too. Note you need a real serial port, the crap they put in laptops doesn't get enough voltage and the counterfeits you get in USB don't have the right control pins.
• Operation with a minimal number of external components. (You can even turn off the reset switch, but I don't reccomend it.)
• SDCC can compile C files for it!

Example Circuit

Datasheet(pdf)

Example Source

• 0001-intclk.c -- A simple standalone program that pulses B4 and B5 very rapidly, just for an example of a minimal working configuration. Also the hex file for it.

To turn a .c file into a .asm file:

sdcc -S -V -mpic16 -p18f2550 -D__18f2550 --use-non-free \
	file.c -o file.asm

To turn a .asm file into a .o file:

gpasm -c file.asm

To link multiple .o files into one .hex file:

gplink -m -s /usr/share/gputils/lkr/18f2550.lkr \
	-o output.hex /usr/share/sdcc/non-free/lib/pic16/libdev18f2550.lib \
	file1.o file2.o file3.o

To burn a .hex file to your PIC:

picprog --device=pic18f2550 --erase --burn \
	--pic-serial-port=/dev/ttyS0 --input-hexfile output.hex

picprog outputs many warnings about configuration registers for this processor, but this seems to be normal.

• This page is extremely new. I don't have a lot here yet.