pimoroni-pico/micropython/examples/servo2040/current_meter.py

import gc
import time
from machine import Pin
from pimoroni import Analog, AnalogMux, Button
from plasma import WS2812
from servo import ServoCluster, servo2040

"""
An example of how to use Servo 2040's current measuring
ability and display the value on the onboard LED bar.

Press "Boot" to exit the program.

NOTE: ServoCluster and Plasma WS2812 use the RP2040's PIO system,
and as such may have problems when running code multiple times.
If you encounter issues, try resetting your board.
"""

BRIGHTNESS = 0.4      # The brightness of the LEDs
UPDATES = 50          # How many times to update LEDs and Servos per second
MAX_CURRENT = 3.0     # The maximum current, in amps, to show on the meter
SAMPLES = 50          # The number of current measurements to take per reading
TIME_BETWEEN = 0.001  # The time between each current measurement

# Free up hardware resources ahead of creating a new ServoCluster
gc.collect()

# Create a servo cluster for pins 0 to 7, using PIO 0 and State Machine 0
START_PIN = servo2040.SERVO_1
END_PIN = servo2040.SERVO_8
servos = ServoCluster(pio=0, sm=0, pins=list(range(START_PIN, END_PIN + 1)))

# Set up the shared analog inputs
cur_adc = Analog(servo2040.SHARED_ADC, servo2040.CURRENT_GAIN,
                 servo2040.SHUNT_RESISTOR, servo2040.CURRENT_OFFSET)

# Set up the analog multiplexer, including the pin for controlling pull-up/pull-down
mux = AnalogMux(servo2040.ADC_ADDR_0, servo2040.ADC_ADDR_1, servo2040.ADC_ADDR_2,
                muxed_pin=Pin(servo2040.SHARED_ADC))

# Create the LED bar, using PIO 1 and State Machine 0
led_bar = WS2812(servo2040.NUM_LEDS, 1, 0, servo2040.LED_DATA)

# Create the user button
user_sw = Button(servo2040.USER_SW)

# Start updating the LED bar
led_bar.start()

# Enable all servos (this puts them at the middle).
# The servos are not going to be moved, but are activated to give a current draw
servos.enable_all()

# Read sensors until the user button is pressed
while not user_sw.raw():

    # Select the current sense
    mux.select(servo2040.CURRENT_SENSE_ADDR)

    # Read the current sense several times and average the result
    current = 0
    for i in range(SAMPLES):
        current += cur_adc.read_current()
        time.sleep(TIME_BETWEEN)
    current /= SAMPLES

    # Print out the current sense value
    print("Current =", round(current, 4))

    # Convert the current to a percentage of the maximum we want to show
    percent = (current / MAX_CURRENT)

    # Update all the LEDs
    for i in range(servo2040.NUM_LEDS):
        # Calculate the LED's hue, with Red for high currents and Green for low
        hue = (1.0 - i / (servo2040.NUM_LEDS - 1)) * 0.333

        # Calculate the current level the LED represents
        level = (i + 0.5) / servo2040.NUM_LEDS
        # If the percent is above the level, light the LED, otherwise turn it off
        if percent >= level:
            led_bar.set_hsv(i, hue, 1.0, BRIGHTNESS)
        else:
            led_bar.set_hsv(i, hue, 1.0, 0.0)

# Disable the servos
servos.disable_all()

# Turn off the LED bar
led_bar.clear()