A question on the brake functionality as there seems to be more to the picture than mentioned on the product page. I've been testing with a voltmeter and have found:
All the below examples are with pwm at 255:
dir low + brake low = reverse (4V on -) ... seems right
dir high + brake low = forward (4V on +) ... seems right
dir low + brake high = coast (~0V on + & -) ... didn't expect this
dir high + brake high = brake(4V on + & -) ... seems right
Also, with all three low (the default state) we seem to have 1.34V to both + & - which is not a hard brake, but is also not coast. I didn't expect this either.
I assume all this is correct behavior. Can someone explain those two unexpected cases to me?
The circuit on that board uses an XNOR gate to derive the actual H-bridge
inputs from the direction pin. The brake signal goes to the XNOR too.
When brake low, this means the gate inverts the direction signal so that
direction selects one direction or the other.
When brake is high the XNOR behaves as a simple buffer, so the drives
are the same - DIR low means neither are driven (coast), DIR high means
both are driven (shorting the motor, braking).