keybrd/tutorials/tutorial_10_writing_IOE_port_classes.md

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/](SPI or I2C). 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: PortMCP23S17 PortWrite_MCP23S17 PortRead_MCP23S17
• I2C I/O expander port classes: PortWrite_PCA9655E PortRead_PCA9655E

6. Write the port classes for your I/O expander. Debugging I/O expander code is hard because SPI or I2C protocol adds a level of indirection.

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.