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

dac.noise(freq)

Generate a pseudo-random noise signal. A new random sample is written to the DAC output at the given frequency.

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.

dac.write(value)

Direct access to the DAC output (8 bit only at the moment).

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.