Keyboard Builders' Digest / Tips & Tricks
On IO expanders
Using an IO expander instead of a second Pro Micro? Posted by scissor_rock_paper.
Published June 19, 2021
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At first sight, this may look like just another handwired split project.
What makes this quite unusual is the IO expander used instead of a second Pro Micro.
The MCP23017 IO expander has 16 IO pins and uses I2C to communicate with the microcontroller (in contrast to the MCP23S17 using serial connection).
I used the Ferris firmware as a starting point for my firmware and only had to make a few small tweaks to get it working with the additional rows.
Next part of the build log is on the way. In the meantime, here is the blog post about the basic electrical design of the project: http://mark-story.com/posts/view/building-a-split-keyboard-part-2
Published on Sat 19th Jun 2021. Featured in KBD #31 (source).
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