OpenTronic

I made this Instructable in late 2016 so the firmware has probably changed since then. I checked the Marlin website now, and it looks like you need to define a dummy thermistor (998) with a set temperature then set TEMP_SENSOR_0 998. If you're using the latest Marlin version.

The processing sketch expects a baud rate of 19200 but not all thermal printers are factory set to that value. Follow the instructions here: https://cdn-learn.adafruit.com/downloads/pdf/mini-thermal-receipt-printer.pdf (page 7) to print a test page, which will tell you the baud rate. If it's not 19200, change the baud rate in the processing sketch to match the value on the test page. If that doesn't help, increase the delay between the lines of the bitmap - where it says delay(20); within the two 'for' loops. Set it to a high value like 500 - the print will be slow, but if it prints correctly with the larger delay, gradually reduce it to find the fastest you can print without missing lines. Hope that helps, and if you have any more trouble leave more comments.

Thanks, it's nice to get back to basics. I've been building a CNC router recently which involves buying a lot of new materials, and it's useful to remember that you can do a lot with things you have lying around the shop.