Currently, this feature isn't supported on splits, spent about an hour troubleshooting my board and firmware before asking, and turns out it's not in place. Note added to save others from this in the future.
* Add files via upload * Update readme.md * Update readme.md * Update readme.md * Add files via upload * Delete split_util.h * Delete split_util.c * Delete serial.h * Delete serial.c * Delete matrix.c * Delete i2c.h * Delete i2c.c * Update rules.mk * Update config.h * Update readme.md * Update readme.md