Added sensor reading example, with mux support

micropython/examples/servo2040/read_sensors.py

@@ -0,0 +1,42 @@
+import time
+from machine import Pin
+from pimoroni import Analog, AnalogMux, Button
+from servo import servo2040
+
+# Press "Boot" to exit the program.
+
+# Create the user button
+user_sw = Button(servo2040.USER_SW)
+
+# Set up the shared analog inputs
+sen_adc = Analog(servo2040.SHARED_ADC)
+vol_adc = Analog(servo2040.SHARED_ADC, servo2040.VOLTAGE_GAIN)
+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))
+
+# Set up the sensor addresses and have them pulled down by default
+sensor_addrs = list(range(servo2040.SENSOR_1_ADDR, servo2040.SENSOR_6_ADDR + 1))
+for addr in sensor_addrs:
+    mux.configure_pull(addr, Pin.PULL_DOWN)
+
+
+# Read sensors until the user button is pressed
+while user_sw.raw() is not True:
+
+    # Read each sensor in turn and print its voltage
+    for i in range(len(sensor_addrs)):
+        mux.select(sensor_addrs[i])
+        print("S", i + 1, " = ", round(sen_adc.read_voltage(), 3), sep="", end=", ")
+
+    # Read the voltage sense and print the value
+    mux.select(servo2040.VOLTAGE_SENSE_ADDR)
+    print("Voltage =", round(vol_adc.read_voltage(), 4), end=", ")
+
+    mux.select(servo2040.CURRENT_SENSE_ADDR)
+    print("Current =", round(cur_adc.read_current(), 4))
+
+    time.sleep(0.5)

micropython/examples/servo2040/servo_led_wave.py

@@ -14,7 +14,7 @@ from servo import ServoCluster, servo2040
 
 SPEED = 5             # The speed that the LEDs will cycle at
 BRIGHTNESS = 0.4      # The brightness of the LEDs
-UPDATES = 50          # How many times the LEDs and Servos will be updated per second
+UPDATES = 50          # How many times to update LEDs and Servos per second
 SERVO_EXTENT = 80.0   # How far from zero to move the servos
 
 # Create a servo cluster for pins 0 to 7, using PIO 0 and State Machine 0

micropython/modules/servo/servo.c

@@ -167,6 +167,8 @@ 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_current_offset = {{&mp_type_float}, -0.02f};
 
 /***** Globals Table *****/
 STATIC const mp_map_elem_t servo2040_globals_table[] = {
@@ -211,7 +213,9 @@ STATIC const mp_map_elem_t servo2040_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_VOLTAGE_SENSE_ADDR), MP_ROM_INT(0b110) },
     { MP_ROM_QSTR(MP_QSTR_CURRENT_SENSE_ADDR), MP_ROM_INT(0b111) },
     { MP_ROM_QSTR(MP_QSTR_SHUNT_RESISTOR), MP_ROM_PTR(&servo2040_shunt_resistor) },
-    { MP_ROM_QSTR(MP_QSTR_ADC_GAIN), MP_ROM_INT(69) },
+    { MP_ROM_QSTR(MP_QSTR_CURRENT_GAIN), MP_ROM_INT(69) },
+    { MP_ROM_QSTR(MP_QSTR_VOLTAGE_GAIN), MP_ROM_PTR(&servo2040_voltage_gain) },
+    { MP_ROM_QSTR(MP_QSTR_CURRENT_OFFSET), MP_ROM_PTR(&servo2040_current_offset) },
 };
 STATIC MP_DEFINE_CONST_DICT(mp_module_servo2040_globals, servo2040_globals_table);
 

micropython/modules_py/pimoroni.py

@@ -7,13 +7,14 @@ PICO_EXPLORER_I2C_PINS = {"sda": 20, "scl": 21}
 
 
 class Analog:
-    def __init__(self, pin, amplifier_gain=1, resistor=0):
+    def __init__(self, pin, amplifier_gain=1, resistor=0, offset=0):
         self.gain = amplifier_gain
         self.resistor = resistor
+        self.offset = offset
         self.pin = ADC(pin)
 
     def read_voltage(self):
-        return self.pin.read_u16() * 3.3 / 65535 / self.gain
+        return max((((self.pin.read_u16() * 3.3) / 65535) + self.offset) / self.gain, 0.0)
 
     def read_current(self):
         if self.resistor > 0:
@@ -22,6 +23,58 @@ class Analog:
             return self.read_voltage()
 
 
+class AnalogMux:
+    def __init__(self, addr0, addr1=None, addr2=None, en=None, muxed_pin=None):
+        self.addr0_pin = Pin(addr0, Pin.OUT)
+        self.addr1_pin = Pin(addr1, Pin.OUT) if addr1 is not None else None
+        self.addr2_pin = Pin(addr2, Pin.OUT) if addr2 is not None else None
+        self.en_pin = Pin(en, Pin.OUT) if en is not None else None
+        self.max_address = 0b001
+        if addr1 is not None:
+            self.max_address = 0b011
+            if addr2 is not None:
+                self.max_address = 0b111
+        self.pulls = [None] * (self.max_address + 1)
+        self.muxed_pin = muxed_pin
+
+    def select(self, address):
+        if address < 0:
+            raise ValueError("address is less than zero")
+        elif address > self.max_address:
+            raise ValueError("address is greater than number of available addresses")
+        else:
+            if self.muxed_pin and self.pulls[address] is None:
+                self.muxed_pin.init(Pin.IN, None)
+
+            self.addr0_pin.value(address & 0b001)
+
+            if self.addr1_pin is not None:
+                self.addr1_pin.value(address & 0b010)
+
+            if self.addr2_pin is not None:
+                self.addr2_pin.value(address & 0b100)
+
+            if self.en_pin is not None:
+                self.en_pin.value(1)
+
+            if self.muxed_pin and self.pulls[address] is not None:
+                self.muxed_pin.init(Pin.IN, self.pulls[address])
+
+    def disable(self):
+        if self.en_pin is not None:
+            self.en_pin.value(0)
+        else:
+            raise RuntimeError("there is no enable pin assigned to this mux")
+
+    def configure_pull(self, address, pull=None):
+        if address < 0:
+            raise ValueError("address is less than zero")
+        elif address > self.max_address:
+            raise ValueError("address is greater than number of available addresses")
+        else:
+            self.pulls[address] = pull
+
+
 class Button:
     def __init__(self, button, invert=True, repeat_time=200, hold_time=1000):
         self.invert = invert