Today we’re going to send some Spanish text to an Epson TM-T20 thermal receipt printer. This post is intended for people who know how to send ASCII to a similar printer, but can’t get the diacritics from Spanish to displayu properly, characters like á, é, í, ó, ñ, ú or ü.
Many receipt printers understand a language called ESC/POS, which uses legacy code pages for non-ASCII text.
Spanish is very easy to encode manually, because it can be represented fully using just Code Page 437, which happens to be the default code page on most receipt printers.
To convert UTF-8 to CP437, I will use the iconv utility on the Linux command-line. API’s for encoding conversion are available for your favourite programming language:
echo "áéíóñúü" | iconv --from-code=UTF-8 --to-code=CP437
Or, as a more complete example, let’s use a pangram from here:
“Benjamín pidió una bebida de kiwi y fresa; Noé, sin vergüenza, la más exquisita champaña del menú”
echo "Benjamín pidió una bebida de kiwi y fresa; \
Noé, sin vergüenza, la más exquisita champaña del menú" | \
iconv --from-code=UTF-8 --to-code=CP437
Next, let’s send some text to the printer. I have a USB printer on Linux, so this is how I print:
echo "Hello World" > /dev/usb/lp0
And putting it all together:
echo "Benjamín pidió una bebida de kiwi y fresa; \
Noé, sin vergüenza, la más exquisita champaña del menú" | \
iconv --from-code=UTF-8 --to-code=CP437 > /dev/usb/lp0
Libraries for PHP and Python users
I’ve helped out writing the internationalization features for two printing libraries (escpos-php and python-escpos), so that programmers can work with text in UTF-8, and let the library translate the text to something that your printer understand.
The same example above, if you use the PHP library, would look like this:
<?php
require __DIR__ . '/vendor/autoload.php';
use Mike42\Escpos\PrintConnectors\FilePrintConnector;
use Mike42\Escpos\Printer;
$connector = new FilePrintConnector("/dev/usb/lp0");
$printer = new Printer($connector);
$printer -> text("Benjamín pidió una bebida de kiwi y fresa; Noé, sin vergüenza, la más exquisita champaña del menú\n");
$printer -> cut();
$printer -> close();
And in Python, it would look like this:
from escpos import *
my_printer = printer.File("/dev/usb/lp0")
my_printer.text("Benjamín pidió una bebida de kiwi y fresa; Noé, sin vergüenza, la más exquisita champaña del menú\n")
my_printer.cut()
Most of the time you need more than text: Formatting, adding barcodes, or cutting the paper will all need ESC/POS commands, and these libraries will help with that too.
Take a look at the project links for more detail.