83 lines
3.0 KiB
ReStructuredText
83 lines
3.0 KiB
ReStructuredText
.. _pyb.ADC:
|
|
|
|
class ADC -- analog to digital conversion
|
|
=========================================
|
|
|
|
.. only:: port_pyboard
|
|
|
|
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
|
|
------------
|
|
|
|
|
|
.. only:: port_pyboard
|
|
|
|
.. 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
|
|
-------
|
|
|
|
.. only:: port_pyboard
|
|
|
|
.. method:: adc.read()
|
|
|
|
Read the value on the analog pin and return it. The returned value
|
|
will be between 0 and 4095.
|
|
|
|
.. method:: 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.
|