USB printer driver for Teensy 3.6 and Teensy 4.1 USB host library
The following library send printer ESC/POS commands for different font sizes, graphics mode, etc. It is based on the Adafruit Thermal printer library but modified to work with USB thermal receipt printers.
https://github.com/gdsports/ESC_POS_Printer
December 5, 2020 Tested with Teensy 3.6 and 4.1 using Arduino IDE 1.8.13 and Teensyduino 1.53.