brainfuck compiler for AVRs

BFC - well, the title is pretty self explanatory. It compiles bf instructions.

How to compile

Make sure you have avr-libc and make, avrdude. Have your brainfuck code in src/src.bf (terminal arguments not added yet). Then do:

$ cd src
$ make clean all

It compiles src.bf into out.bin, which objcopy turns into the out.hex file. Change programmer settings (AVRDUDE_TARGET and PROGRAMMER) in src/Makefile and do

$ make flash

If you'd like to see what the brainfuck commands were turned to in assembly, do

$ make bfdisasm

And take a look inside the bfdisasm file. It will look something like this:

[
	68:	0c 91       	ld	r16, X
	6a:	00 30       	cpi	r16, 0x00	; 0
	6c:	11 f4       	brne	.+4      	;  0x72
	6e:	0c 94 5e 00 	jmp	0xbc	;  0xbc

-
	72:	0c 91       	ld	r16, X
	74:	0a 95       	dec	r16
	76:	0c 93       	st	X, r16

etc.

How this works ?

Well.. In bf you have a tape of bytes. In this case, the tape is the built in SRAM of AVR. The program navigates over RAM using > and <. The + and - just do INC and DEC.

For simplicity, all jumps and loads were done directly (mostly).

Change in plans. In the boot time, the starting address for the 'tape' is loaded in the X register. After what, all calls are done indirectly. So for example + will just do

ld r16, X
inc r16
st x, r16

While the > and < just do a load with post/pre increment/decrement.

ld r2, X+

or

ld r2, -X

In the /avr directory, there is the source code of prologue and output communication stuff.

What works is implemented ?

Not fully tested, but everything except , (input command)

Prologue

Basic set-up of UART0 in 9600 baud. All the usable RAM gets zeroed.

The other part

Sends the character, waits for UART to finish.

TODO

Well, maybe implement input from UART, and some optimizations.

In this version the optimization level is low (like, reallly low). But maybe in future versions (if any) it will be fixed.