I tried a standard config (think BFO-9000 default config). Here are some numbers. Main refers to the left half of the keyboard connected to USB. "Other" refers

I tried a standard config (think BFO-9000 default config). Here are some numbers. Main refers to the left half of the keyboard connected to USB. "Other" refers to the right half, connected via a TRRS cable to the left half. Serial for comms, measurement on main half, other half disconnected. 7-13ms Serial, measurement on main half, other half connected. 8-16ms Serial, measurement on other half, main connected. 9-19ms i2c, measurement on main, other not connected, 5-15ms i2c, measurement on main, other connected, 6-16ms i2c, measurement on other, 10-20ms Not sure if any of the above is stat-sig. Measurement methodology - hook up one probe to the key and trigger on having the key scan seeing "key down". The other probe went to two pins I designated as a NumLock LED. In terms of matrix refresh rate - I remember that enabling reporting to console slowed things down significantly, i2c slowed things down, enabling features slowed things down. No hard numbers unfortunately. ZMK - just because it's a fresher codebase & support for 32-bit only. I did no measurements of ZMK.