class ADC – analog to digital conversion

Usage:

import pyb

adc = pyb.ADC(pin)              # create an analog object from a pin
val = adc.read()                # read an analog value

adc = pyb.ADCAll(resolution)    # creale an ADCAll object
val = adc.read_channel(channel) # read the given channel
val = adc.read_core_temp()      # read MCU temperature
val = adc.read_core_vbat()      # read MCU VBAT
val = adc.read_core_vref()      # read MCU VREF

Constructors

class pyb.ADC(pin)

Create an ADC object associated with the given pin. This allows you to then read analog values on that pin.

Methods

adc.read()

Read the value on the analog pin and return it. The returned value will be between 0 and 4095.

adc.read_timed(buf, timer)

Read analog values into buf at a rate set by the timer object.

buf can be bytearray or array.array for example. The ADC values have 12-bit resolution and are stored directly into buf if its element size is 16 bits or greater. If buf has only 8-bit elements (eg a bytearray) then the sample resolution will be reduced to 8 bits.

timer should be a Timer object, and a sample is read each time the timer triggers. The timer must already be initialised and running at the desired sampling frequency.

To support previous behaviour of this function, timer can also be an integer which specifies the frequency (in Hz) to sample at. In this case Timer(6) will be automatically configured to run at the given frequency.

Example using a Timer object (preferred way):

adc = pyb.ADC(pyb.Pin.board.X19)    # create an ADC on pin X19
tim = pyb.Timer(6, freq=10)         # create a timer running at 10Hz
buf = bytearray(100)                # creat a buffer to store the samples
adc.read_timed(buf, tim)            # sample 100 values, taking 10s

Example using an integer for the frequency:

adc = pyb.ADC(pyb.Pin.board.X19)    # create an ADC on pin X19
buf = bytearray(100)                # create a buffer of 100 bytes
adc.read_timed(buf, 10)             # read analog values into buf at 10Hz
                                    #   this will take 10 seconds to finish
for val in buf:                     # loop over all values
    print(val)                      # print the value out

This function does not allocate any memory.

The ADCAll Object

Instantiating this changes all ADC pins to analog inputs. It is possible to read the MCU temperature, VREF and VBAT without using ADCAll. The raw data can be accessed on ADC channels 16, 17 and 18 respectively. However appropriate scaling will need to be applied.