circuitpython/docs/library/pyb.DAC.rst

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.. _pyb.DAC:
2014-10-31 18:21:37 -04:00
class DAC -- digital to analog conversion
=========================================
The DAC is used to output analog values (a specific voltage) on pin X5 or pin X6.
The voltage will be between 0 and 3.3V.
*This module will undergo changes to the API.*
Example usage::
from pyb import DAC
dac = DAC(1) # create DAC 1 on pin X5
dac.write(128) # write a value to the DAC (makes X5 1.65V)
To output a continuous sine-wave::
import math
from pyb import DAC
# create a buffer containing a sine-wave
buf = bytearray(100)
for i in range(len(buf)):
buf[i] = 128 + int(127 \* math.sin(2 \* math.pi \* i / len(buf)))
# output the sine-wave at 400Hz
dac = DAC(1)
dac.write_timed(buf, 400 \* len(buf), mode=DAC.CIRCULAR)
Constructors
------------
.. class:: pyb.DAC(port)
Construct a new DAC object.
``port`` can be a pin object, or an integer (1 or 2).
DAC(1) is on pin X5 and DAC(2) is on pin X6.
Methods
-------
.. method:: dac.noise(freq)
Generate a pseudo-random noise signal. A new random sample is written
to the DAC output at the given frequency.
.. method:: dac.triangle(freq)
Generate a triangle wave. The value on the DAC output changes at
the given frequency, and the frequence of the repeating triangle wave
itself is 2048 times smaller.
.. method:: dac.write(value)
Direct access to the DAC output (8 bit only at the moment).
.. method:: dac.write_timed(data, freq, \*, mode=DAC.NORMAL)
Initiates a burst of RAM to DAC using a DMA transfer.
The input data is treated as an array of bytes (8 bit data).
``mode`` can be ``DAC.NORMAL`` or ``DAC.CIRCULAR``.
TIM6 is used to control the frequency of the transfer.