Got it working. I was using pin 1 (PB5), which I thought I could use, but apparently you can only use the reset pin under certain conditions. At first I was getting some inconsistent button presses. Setting CTRL_CLK to 8 fixed it for me.

I am using it with an RF module to make it wireless. At the moment I’m simply intercepting PS2data and sending the first 9 bytes over to the receiver. Works ok, but latency at only 2000bps is a bit too much. Sending individual events should make it snappier I hope.