Tutorial 10 - writing new IOE Port classes

Port classes are the keybrd library’s interface to I/O expander ports.

Steps to writing a new port class:

1. Get a copy of the I/O expander’s datasheet.
2. An I/O expander will use one of two communication protocols: http://www.byteparadigm.com/applications/introduction-to-i2c-and-spi-protocols/. Refer to the Arduino SPI or Arduino Wire (I2C) library
3. Get familiar with your I/O expander.
   • Different I/O expanders use different commands (a.k.a. operation codes). Refer to your I/O expander’s datasheet for read and write commands.
   • Search for Arduino sketch examples containing your I/O expander (sumotoy has a large gpio expander library).
4. Study a simple keybrd sketch that uses an I/O expander.
   • SPI I/O expander example sketch
   • I2C I/O expander example sketch
5. Study other keybrd port classes.
   • SPI I/O expander port classes: Port_MCP23S17
   • I2C I/O expander port classes: Port_PCA9655E
6. Write the port classes for your I/O expander.
   • Example shows how Port_PCA9655E was developed in stages, from fundamental to practical
   • Debugging I/O expander code is hard because SPI or I2C protocol, expander configuration, and expander commands.

keybrd tutorial by Wolfram Volpi is licensed under a Creative Commons Attribution 4.0 International License.
Permissions beyond the scope of this license may be available at https://github.com/wolfv6/keybrd/issues/new.