arduino/phyduino_pico/analog_differential/main.py

Measures the voltage between two analogue pins, e.g. across a resistor or a sensor bridge, twice a second.

Arduino has no differential reading, so this uses the phyduino.py functions.

• A3 - A4: true differential. The on-board ADC samples both pins at the same instant, so noise common to both cancels. Range ±1024 mV in 0.5 mV steps (a larger difference is measured as two separate readings).
• A0 - A1: computed from readings taken one after the other. Fine for slow signals, but noise on both pins does not cancel.

Wiring

Keep every pin between 0 V and its full scale (A0-A2: 3.3 V, A3-A5: 2.048 V).

Output

A3 - A4:   100.0 mV    A0 - A1:    99.1 mV

# Measures the voltage between two analogue pins, e.g. across a resistor or a
# sensor bridge, twice a second.
#
# A3 - A4: true differential. The on-board ADC samples both pins at the same
#   instant, so noise common to both cancels. Range +/-1024 mV in 0.5 mV steps
#   (a larger difference is measured as two separate readings).
# A0 - A1: computed from readings taken one after the other.
#   Fine for slow signals, but noise on both pins does not cancel.
#
# Keep every pin between 0 V and its full scale (A0-A2: 3.3 V, A3-A5: 2.048 V).
# Arduino has no differential reading, so this uses the phyduino functions.
 
from arduino import *  # the Arduino-style functions: pinMode(), digitalWrite(), delay(), ...
import phyduino as mcu  # the Phyduino Pico library, for mcu.analog_differential_millivolts()
 
 
def setup():
    mcu.analog_averaging(16)  # average 16 samples per reading, for steadier numbers
 
 
def loop():
    # The voltage of the first pin minus the second, in millivolts. "%7.1f" shows
    # each with one decimal place, right-aligned in 7 characters.
    print("A3 - A4: %7.1f mV    A0 - A1: %7.1f mV" % (
        mcu.analog_differential_millivolts(A3, A4),  # sampled at the same instant
        mcu.analog_differential_millivolts(A0, A1)))  # two readings, one after the other
    delay(500)  # twice a second
 
 
# Do not edit below this line: it runs setup() once, then loop() over and over.
def main():
    setup()  # runs once, at the start
    while True:  # repeats until stopped: Interrupt in PyCharm, or mpremote soft-reset
        loop()
 
 
# True when this file is run, but not when another file imports it.
if __name__ == "__main__":
    main()