Measuring encoder count for movement

We know what sequences to expect for our encoder, and we have a working knowledge of PIO assembler. So, we can bring these together to create the counter. We’ll start simple though; let’s see how to detect when a system has changed.

Making a simple PIO change detection loop

As we saw in the read two pins example, when we output the system’s state in a tight loop, it floods off anything interesting. We are interested in state changes, a step toward the full decoder. In the pio_one_encoder_when_changed.py file, we go straight from imports into the assembler:

import board
import rp2pio
import adafruit_pioasm
import array

We start by clearing y –; we are going to use y to store a pin value for comparison:

program = """
    set y, 0

The following code creates a read label; we can loop to this point to get new pin readings. It stores the old y in x so that we can get a new...