Half-decent LED-PWM and capacitive-sense GPIO coroutines (in micropython, on GHI Electronics G30TH -- essentiall Nucleo F401 but with different pins and pin names)

main.py

import pyb
from pyb import Timer

# timer 2 will be created with a frequency of 10 kHz
tim=pyb.Timer(4,freq=10000);
# attach the timer to the LED GPIO, turning the brightness OFF to begin
tchannel = tim.channel(3, Timer.PWM, pin=pyb.Pin.board.JP32, pulse_width_percent=0)

# setup comm channel, for debug prints
# uart = pyb.UART(2, 9600)                         # init with given baudrate
# uart.init(9600, bits=8, parity=None, stop=1)

glob_max = glob_min = glob_span = 0

max_num_check_cycles = 50000


update_func = None

def later_update_func(current):
    """
    use the min and max to calculate a range of sensor readings, then normalize the current reading
    finally scale the normalized reading to a 0-100 percentage value, cast to Integer
    then finally update the Timer PWM percentage
    """
    global glob_min
    global glob_max
    global glob_span
    global tchannel
    glob_max = max(current, glob_max)
    glob_min = min(current, glob_min)
    glob_span = glob_max - glob_min
    if (glob_span) > 0:
        glob_dly = (((current-glob_min)/(glob_span))*100)
        glob_dly = int(glob_dly)
    tchannel.pulse_width_percent(glob_dly)
    # uart.write('LATER UPDATE {}\n'.format(glob_dly))

def first_update_func(i):
    """
    set up the initial values for min and max of sensor range, 
    then switch the update func to "later_update_func" (I think this avoids an "if" branch code)
    """
    global glob_min
    global glob_max
    global update_func
    glob_max = i
    glob_min = i
    update_func = later_update_func
    # uart.write('FIRST UPDATE\n')

update_func = first_update_func

def gpio_cap_sense():
    """
    GPIO capacitive sense
    """
    global update_func
    while True:
        # Discharge the pin first by setting it low and output
        g = pyb.Pin(pyb.Pin.board.JP25, pyb.Pin.OUT_PP, pyb.Pin.PULL_NONE)
        g.value(True)
        pyb.delay(1)

        # Make the pin an input WITHOUT the internal pull-up on
        g = pyb.Pin(pyb.Pin.board.JP25, pyb.Pin.IN, pyb.Pin.PULL_NONE)
        i=0

        # Now see how many cycles it takes to get the pin pulled up
        while i<max_num_check_cycles:
            # apparently there is some inverter,
            # such that I need to check when the pin goes apparently-low???
            if not g.value():
                update_func(i)
                break
            i+=1
        yield

# set up co-tasks
tasks = [gpio_cap_sense()]

# loop through each task forever
while 1: 
    for t in tasks:
        next(t)