Fix calibration

Removed internal calibration since the code was too expensive in flash
size, calibration is now possible only from an external script.

Fixed the code for the PWM output to be without internal constants so
that the external calibration doesn't need to know anything special
about the internal calculations beyond the y=ax+b assumption.

Added a calibrate.py script to calibrate the vout, both ADC and PWM.

stm8/Makefile

@@ -1,4 +1,4 @@
-SRC=main.c display.c uart.c eeprom.c outputs.c config.c calibrate.c fixedpoint.c parse.c adc.c
+SRC=main.c display.c uart.c eeprom.c outputs.c config.c fixedpoint.c parse.c adc.c
 CFLAGS= -lstm8 -mstm8 --opt-code-size --std-c99
 OBJ=$(SRC:.c=.rel)
 DEP=$(SRC:%.c=.%.c.d)
@@ -33,9 +33,6 @@ test_adc_accuracy: test_adc_accuracy.c config.c adc.c fixedpoint.c
 test_parse: test_parse.c parse.c
 	gcc -g -Wall -o $@ $< -DTEST=1
 
-test_calibration: test_calibration.c calibrate.c
-	gcc -g -Wall -o $@ $< -DTEST=1
-
 clean:
 	-rm -f *.rel *.ihx *.lk *.map *.rst *.lst *.asm *.sym .*.d