148 lines
4.8 KiB
ReStructuredText
148 lines
4.8 KiB
ReStructuredText
.. _pyb.ADC:
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class ADC -- analog to digital conversion
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=========================================
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.. only:: port_pyboard
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Usage::
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import pyb
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adc = pyb.ADC(pin) # create an analog object from a pin
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val = adc.read() # read an analog value
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adc = pyb.ADCAll(resolution) # creale an ADCAll object
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val = adc.read_channel(channel) # read the given channel
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val = adc.read_core_temp() # read MCU temperature
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val = adc.read_core_vbat() # read MCU VBAT
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val = adc.read_core_vref() # read MCU VREF
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.. only:: port_wipy
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Usage::
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import pyb
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adc = pyb.ADC() # create an ADC object
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apin = adc.channel(pin='GP3') # create an analog pin on GP3
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val = apin() # read an analog value
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Constructors
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------------
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.. only:: port_pyboard
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.. class:: pyb.ADC(pin)
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Create an ADC object associated with the given pin.
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This allows you to then read analog values on that pin.
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.. only:: port_wipy
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.. class:: pyb.ADC(id=0, \*, bits=12)
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Create an ADC object associated with the given pin.
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This allows you to then read analog values on that pin.
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For more info check the `pinout and alternate functions
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table. <https://raw.githubusercontent.com/wipy/wipy/master/docs/PinOUT.png>`_
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.. warning::
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ADC pin input range is 0-1.4V (being 1.8V the absolute maximum that it
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can withstand). When GP2, GP3, GP4 or GP5 are remapped to the
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ADC block, 1.8 V is the maximum. If these pins are used in digital mode,
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then the maximum allowed input is 3.6V.
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Methods
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-------
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.. only:: port_pyboard
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.. method:: adc.read()
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Read the value on the analog pin and return it. The returned value
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will be between 0 and 4095.
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.. method:: adc.read_timed(buf, timer)
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Read analog values into ``buf`` at a rate set by the ``timer`` object.
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``buf`` can be bytearray or array.array for example. The ADC values have
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12-bit resolution and are stored directly into ``buf`` if its element size is
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16 bits or greater. If ``buf`` has only 8-bit elements (eg a bytearray) then
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the sample resolution will be reduced to 8 bits.
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``timer`` should be a Timer object, and a sample is read each time the timer
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triggers. The timer must already be initialised and running at the desired
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sampling frequency.
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To support previous behaviour of this function, ``timer`` can also be an
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integer which specifies the frequency (in Hz) to sample at. In this case
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Timer(6) will be automatically configured to run at the given frequency.
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Example using a Timer object (preferred way)::
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adc = pyb.ADC(pyb.Pin.board.X19) # create an ADC on pin X19
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tim = pyb.Timer(6, freq=10) # create a timer running at 10Hz
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buf = bytearray(100) # creat a buffer to store the samples
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adc.read_timed(buf, tim) # sample 100 values, taking 10s
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Example using an integer for the frequency::
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adc = pyb.ADC(pyb.Pin.board.X19) # create an ADC on pin X19
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buf = bytearray(100) # create a buffer of 100 bytes
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adc.read_timed(buf, 10) # read analog values into buf at 10Hz
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# this will take 10 seconds to finish
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for val in buf: # loop over all values
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print(val) # print the value out
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This function does not allocate any memory.
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.. only:: port_wipy
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.. method:: adc.channel(id, *, pin)
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Create an analog pin. If only channel ID is given, the correct pin will be selected. Alternatively,
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only the pin can be passed and the correct channel will be selected. Examples::
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# all of these are equivalent and enable ADC channel 1 on GP3
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apin = adc.channel(1)
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apin = adc.channel(pin='GP3')
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apin = adc.channel(id=1, pin='GP3')
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.. method:: adc.init()
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Enable the ADC block.
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.. method:: adc.deinit()
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Disable the ADC block.
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.. only:: port_wipy
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class ADCChannel --- read analog values from internal or external sources
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=========================================================================
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.. only:: port_wipy
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ADC channels can be connected to internal points of the MCU or to GPIO pins.
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ADC channels are created using the ADC.channel method.
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.. method:: adcchannel()
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Fast method to read the channel value.
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.. method:: adcchannel.value()
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Read the channel value.
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.. method:: adcchannel.init()
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Re-init (and effectively enable) the ADC channel.
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.. method:: adcchannel.deinit()
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Disable the ADC channel.
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