Quad Encoder Problem

[RossWaddell]

I have to admit, Ioannis, the code was grabbed from an example here and implemented on my side using a Grayhill encoder which only triggered the interrupt once per detent. Works perfectly with that device, With the CUI ACZ11, I added the check on the ISRCounter but it **does** work - both CW & CCW rotations are captured correctly.

[RossWaddell]

I tried CCW rotation again last night and it does seem to get confused every once in a while - either decrements by 2 or sometimes even increments. Doesn't happen often enough to be too much of a problem, but I would like to make the code as efficient as possible.

Not sure what else I can do in the ISR, though. If I only need one edge to check the rotation direction then I could do as Henrik suggested and turn off 2 of the edge interrupts; that way, it would only hit the ISR twice. I could do the RotEncDir determination on the first interrupt then set a flag to ignore the 2nd interrupt, then reset those after the 2nd.

[Ioannis]

I stil cannot see how this piece of code can be true:

RotEncDir = New_Bits.1 ^ Old_Bits.0
    IF RotEncDir = 1 Then

If you follow what Henrik has posted on that pulse train diagram at #21, you will see that after the above XOR, the IF RotEncDir = 1 statement will always fail and the ELSE will be executed.

Ioannis

[RossWaddell]

The New_Bits will be the same for A & B, but the Old_Bits should still have PORTA.0 (B pin of encoder) as 1 for the last falling edge interrupt, won't it?

[Ioannis]

I don't think so after the 4 step counter. At that moment both will be zero.

Ioannis

[RossWaddell]

But experimentally it works, both for CW & CCW. I'd love to optimize this code for full quad cycle encoders like the CUI ACZ11 one I'm using, but I'm at a loss as to what to change (other than trying Henrik's suggestion of reducing the number of edges to 2 from 4).

[HenrikOlsson]

Hi,
Change the code so that you interrupt on one edge of one channel - only. (The rising edge of channel A for example).
In the ISR, poll "the other" channel, if it's low you're moving in one direction, if it's high you're moving in the other.
Verify that it works at "any" speed you may turn the encoder.

/Henrik.