calibrate.py

#!/usr/bin/python
#
# Thermal calibration utility for Adafruit_Thermal Python library.
# Run this utility before using the printer for the first time, any
# time a different power supply is used, or when using paper from a
# different source.
#
# Prints a series of black bars with increasing "heat time" settings.
# Because printed sections have different "grip" characteristics than
# blank paper, as this progresses the paper will usually at some point
# jam -- either uniformly, making a short bar, or at one side or the
# other, making a wedge shape.  In some cases, the Pi may reset for
# lack of power.
#
# Whatever the outcome, take the last number printed BEFORE any
# distorted bar and enter in in Adafruit_Thermal.py as defaultHeatTime
# (around line 53).
#
# You may need to pull on the paper as it reaches the jamming point,
# and/or just abort the program, press the feed button and take the
# last good number.

from __future__ import print_function
from Adafruit_Thermal import *

printer = Adafruit_Thermal("/dev/ttyAMA0", 19200, timeout=5)

for i in range(0,256,15):
	printer.begin(i)
	printer.println(i)                 # Print heat time
	printer.inverseOn()
	printer.print('{:^32}'.format('')) # Print 32 spaces (inverted)
	printer.inverseOff()

printer.begin() # Reset heat time to default
printer.feed(4)