kopia lustrzana https://github.com/micropython/micropython
80 wiersze
2.1 KiB
ReStructuredText
80 wiersze
2.1 KiB
ReStructuredText
.. _pyb.DAC:
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class DAC -- digital to analog conversion
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=========================================
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The DAC is used to output analog values (a specific voltage) on pin X5 or pin X6.
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The voltage will be between 0 and 3.3V.
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*This module will undergo changes to the API.*
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Example usage::
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from pyb import DAC
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dac = DAC(1) # create DAC 1 on pin X5
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dac.write(128) # write a value to the DAC (makes X5 1.65V)
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To output a continuous sine-wave::
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import math
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from pyb import DAC
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# create a buffer containing a sine-wave
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buf = bytearray(100)
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for i in range(len(buf)):
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buf[i] = 128 + int(127 \* math.sin(2 \* math.pi \* i / len(buf)))
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# output the sine-wave at 400Hz
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dac = DAC(1)
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dac.write_timed(buf, 400 \* len(buf), mode=DAC.CIRCULAR)
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Constructors
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------------
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.. class:: pyb.DAC(port)
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Construct a new DAC object.
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``port`` can be a pin object, or an integer (1 or 2).
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DAC(1) is on pin X5 and DAC(2) is on pin X6.
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Methods
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-------
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.. method:: dac.noise(freq)
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Generate a pseudo-random noise signal. A new random sample is written
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to the DAC output at the given frequency.
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.. method:: dac.triangle(freq)
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Generate a triangle wave. The value on the DAC output changes at
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the given frequency, and the frequence of the repeating triangle wave
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itself is 2048 times smaller.
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.. method:: dac.write(value)
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Direct access to the DAC output (8 bit only at the moment).
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.. method:: dac.write_timed(data, freq, \*, mode=DAC.NORMAL)
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Initiates a burst of RAM to DAC using a DMA transfer.
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The input data is treated as an array of bytes (8 bit data).
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``freq`` can be an integer specifying the frequency to write the DAC
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samples at, using Timer(6). Or it can be an already-initialised
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Timer object which is used to trigger the DAC sample. Valid timers
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are 2, 4, 5, 6, 7 and 8.
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``mode`` can be ``DAC.NORMAL`` or ``DAC.CIRCULAR``.
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Example using both DACs at the same time::
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dac1 = DAC(1)
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dac2 = DAC(2)
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dac1.write_timed(buf1, pyb.Timer(6, freq=100), mode=DAC.CIRCULAR)
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dac2.write_timed(buf2, pyb.Timer(7, freq=200), mode=DAC.CIRCULAR)
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