8 years, 3 months ago.

Which ARM to use?

One of the tasks I need to do is control a motor's speed and position using a quadrature encoder. Each motor has two sensors 90 degrees apart and there are 64 pulse per revolution. At 10,000 RPM we'd get 128,000 pulses per minute or about 2,000 per second. The system has four motors that need to be speed controlled via a PID loop. The PID loop runs at abut 25Hz and then commands and status info is also exchanged over a serial link to another computer. Other stuff goes on too like measuring the voltage and current of the battery and at each motor. The big processing load, I think is the interrupt which might be a total of 8,000 per second at the worst case. We'd have 6 or 8 tasks running at about 25Hz at most that are pretty simple like monitoring the current and limiting commanded accelerations and such.

This is to much for an Arduino. It can not quite handle all I need for even two motors.

In terms of processing power is this an M0 or an M4 job or what? I need a board that is running at about 50% capasity on day one so there is room for feature creep. Cost, value and power are issues. My guess is that a cortex-M4 at 48MHz with a FPU is enough and with room to grow. But I'm guessing.