Added current meter example, + some fixes

micropython/examples/servo2040/current_meter.py

@@ -0,0 +1,83 @@
+import time
+from machine import Pin
+from pimoroni import Analog, AnalogMux, Button
+from plasma import WS2812
+from servo import ServoCluster, servo2040
+
+# NOTE: ServoCluster lets you control up to 30 servos at once. This is
+# done using the RP2040's PIO system. As such it is experimental and may
+# have edge-cases that will need to be fixed. This is particularly true
+# when attempting to run a program multiple times.
+# If you do encounter issues, try resetting your board.
+
+# Press "Boot" to exit the program.
+
+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
+
+# Create the user button
+user_sw = Button(servo2040.USER_SW)
+
+# 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_DAT)
+
+# 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 user_sw.raw() is not True:
+
+    # 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()

micropython/examples/servo2040/multiple_servos.py

@@ -7,7 +7,7 @@ START_PIN = servo2040.SERVO_1
 END_PIN = servo2040.SERVO_3
 servos = [Servo(i) for i in range(START_PIN, END_PIN + 1)]
 
-# Enable all servos (this puts it at the middle)
+# Enable all servos (this puts them at the middle)
 for s in servos:
     s.enable()
 time.sleep(2)

micropython/examples/servo2040/read_sensors.py

@@ -36,6 +36,7 @@ while user_sw.raw() is not True:
     mux.select(servo2040.VOLTAGE_SENSE_ADDR)
     print("Voltage =", round(vol_adc.read_voltage(), 4), end=", ")
 
+    # Read the current sense and print the value
     mux.select(servo2040.CURRENT_SENSE_ADDR)
     print("Current =", round(cur_adc.read_current(), 4))
 

micropython/modules/servo/servo.c

@@ -167,7 +167,7 @@ typedef struct _mp_obj_float_t {
     mp_float_t value;
 } mp_obj_float_t;
 mp_obj_float_t servo2040_shunt_resistor = {{&mp_type_float}, 0.003f};
-mp_obj_float_t servo2040_voltage_gain = {{&mp_type_float}, 0.5f};
+mp_obj_float_t servo2040_voltage_gain = {{&mp_type_float}, 3.9f / 13.9f};
 mp_obj_float_t servo2040_current_offset = {{&mp_type_float}, -0.02f};
 
 /***** Globals Table *****/