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ADC

The ADC sample demonstrates using the analogio module to measure the voltage of the device power supply.

The measurement circuit contains a voltage divider made of two resistors. AIN0 (alias A0) measures the voltage over the lower resistor and P1.14 (alias MEAS_EN) is used to enable the voltage measurement. The voltage measurement circuitry is shown in the following figure:

Requirements

Before you start, check that you have the required hardware and software:

Running the code

To run the code, complete the following steps:

  1. Connect nRF52840 Connect Kit to your computer using the USB-C Cable.
  2. Start Mu Editor, click Load to open code.py in the CIRCUITPY drive.

  3. Copy and paste the following code into code.py and click Save:

    CIRCUITPY/code.py
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    import time
import board
import digitalio
from analogio import AnalogIn

# Enable measurement
meas_en = digitalio.DigitalInOut(board.MEAS_EN)
meas_en.direction=digitalio.Direction.OUTPUT
meas_en.value = True

# Analog In 
analog_in = AnalogIn(board.A0)

# Measure the voltage of VSYS
def get_voltage(ain):
    return ((ain.value * 3.3) / 65536) * (1000 + 100) / 100

while True:
    print((get_voltage(analog_in),))
    time.sleep(0.1)

  4. Your code will run as soon as the file is done saving. Click Serial on Mu Editor's Top Menu to open a serial console. You should see the console output, similar to what is shown in the following:

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    Code stopped by auto-reload. Reloading soon.

Auto-reload is on. Simply save files over USB to run them or enter REPL to disable.
code.py output:
(5.149,)
(5.30852,)
(5.10468,)
(5.09582,)
(5.11355,)
(5.37942,)
(5.4769,)
(5.18444,)
(5.11355,)
...

  5. You can also use the plotter for data inspection. Click Plotter on Mu Editor's Top Menu to open up a plotter pane: