phyduino/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.

• 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).
 
import time  # sleep() for pauses
 
import phyduino as mcu  # the Phyduino Pico library, used as mcu.<name>
 
mcu.analog_averaging(16)  # average 16 samples per reading, for steadier numbers
 
while True:  # repeats until stopped: Interrupt in PyCharm, or mpremote soft-reset
    # 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
    time.sleep(0.5)  # twice a second