Pico W MPR121 touch keyboard on I2C1

# Electrode keyboard: the MPR121 senses a finger on any of its twelve
# electrodes. It is on I2C1 (SDA GP6, SCL GP7); mpr121.py reads it.
from machine import I2C, Pin
from mpr121 import MPR121
import time

i2c = I2C(1, sda=Pin(6), scl=Pin(7), freq=400000)
touch = MPR121(i2c)
last = []

while True:
    pads = touch.pads()
    if pads != last:
        if pads:
            print("touched", pads)
        last = pads
    time.sleep_ms(20)

# mpr121.py: the MPR121 capacitive touch controller, the few registers
# a touch keyboard needs. touched() returns a 12-bit mask: electrode 0
# is bit 0.
import time

class MPR121:
    def __init__(self, i2c, addr=0x5A):
        self.i2c = i2c
        self.addr = addr
        self._set(0x80, 0x63)            # soft reset
        time.sleep_ms(1)
        self._set(0x5E, 0x00)            # stop, so the setup can be written
        for e in range(12):
            self._set(0x41 + 2 * e, 12)  # touch threshold
            self._set(0x42 + 2 * e, 6)   # release threshold
        self._set(0x5D, 0x04)            # sample timing
        self._set(0x5E, 0x8C)            # run all 12 electrodes

    def _set(self, reg, value):
        self.i2c.writeto_mem(self.addr, reg, bytes([value]))

    def touched(self):
        low, high = self.i2c.readfrom_mem(self.addr, 0x00, 2)
        return (low | high << 8) & 0x0FFF

    def pads(self):
        mask = self.touched()
        return [e for e in range(12) if mask & (1 << e)]