I’m working on a open source midi controller (keyboard). It has a keyboard, an LCD display and 8 rotary encoders. I would like the keyboard matrix (8x24 switches) to be scanned exactly every 1ms (there are to switches under each key for measuring velocity, because of this bouncing is not a big problem). The encoders and LCD is not time critical. I’m using an atmega128 running at 12MHz.
What Tick Frequency would be appropriate?? What is the overhead of the rtos kernel? Instructions / tick, instructions / context switch?