Caution

MOVED! see https://git.alifeee.net/openbenches-thermal-printer/about/

Bench thermal printing

Printing benches from https://openbenches.org/ with a ZJ-5870 ESC/POS thermal printer.

For more information on the bench endpoints, see the transformer.

Installation

Install required python modules

python -m venv env
./env/bin/pip install -r requirements.txt

To install Pillow, some prerequisites might be needed, these are:

sudo apt-get zlib1g-dev
sudo apt-get libjpeg62-turbo-dev
sudo apt-get install build-essential
sudo apt-get install python-dev
pip install pillow

Install cron

The file checkbench.sh checks if the cached bench ID is the same as the current bench ID.

If it is not, it prints the bench using printbench.sh.

This script can be run as a cron, by running crontab -e and entering (change the directory to whatever it is installed to)

*/10 * * * * /home/alifeee/thermalprinter/benches/checkbench.sh >> /home/alifeee/thermalprinter/benches/cron.log 2>&1

Usage

Print latest bench

./printbench.sh

Print 3rd latest bench

./printbench.sh 3

ESC/POS

I use a 58mm ZJ-5890TZJiang_5890T thermal printer (usually ZJ-58 in brief).

There are many drivers. You can also (in Linux) send commands "manually".

Further reading

• http://scruss.com/blog/2014/08/02/notes-on-mini-printers-and-linux/
  • https://github.com/klirichek/zj-58
  • https://github.com/python-escpos/python-escpos
  • https://gist.github.com/scruss/36c31a9b653779b2b7d1 (python print image)
  • https://github.com/adafruit/Python-Thermal-Printer?tab=readme-ov-file
  • http://scruss.com/blog/2015/06/21/just-in-case-you-were-needing-a-thermal-printer-test-image/
• https://scruss.com/blog/2015/07/12/thermal-printer-driver-for-cups-linux-and-raspberry-pi-zj-58/
• https://mike42.me/blog/what-is-escpos-and-how-do-i-use-it

Manual commands

All characters (with printf) can be either plain, octal, or hex. See https://www.asciitable.com/

• plain → b
• octal → \142
• hex → \x62

So the "reset" sequence of ESC @ can be represented as any of:

\e@ \033@ \033\100 \x1b@ \x1b\x40 or probably more

Some commands are

# reset all formatting
printf "\e@" > /dev/usb/lp0
# send "some text"
printf "some text\n" > /dev/usb/lp0
# underline (number is 0 1 or 2)
printf "\033-2" > /dev/usb/lp0
# justified (0 1 or 2 for left/centre/right)
printf "\033a1" > /dev/usb/lp0

Libraries

There are many libraries:

• Python: https://github.com/python-escpos/python-escpos/
• Node: https://github.com/node-escpos/driver
• PHP: https://github.com/mike42/escpos-php

There are also some "standalone" image printing scripts by @scruss:

• Using ESC v https://gist.github.com/scruss/36c31a9b653779b2b7d1
• Using ESC * https://gist.github.com/scruss/95c61c9a1501ada2a6c5

I have had problems with the ESC v one and printing an image with a resolution of 384x288, while 384x289 has worked fine. This was the only difference I could see.

This project

This one uses the Python library. This has drawbacks, such as that you cannot access the printer over /dev/usb/lp0 after using the Python library. I am not sure why. It seems that p.close() should give access of this back to you, but it doesn't seem to. Thus, I do all printing with the library, instead of a mix (which I would prefer).