For all ports, DMA runs continuously in the background and allows user applications to perform other operations while
sample data is transfered between the internal buffer and the I2S peripheral unit.
For all ports, DMA runs continuously in the background and allows user applications to perform other operations while
sample data is transfered between the internal buffer and the I2S peripheral unit.
Increasing the size of the internal buffer has the potential to increase the time that user applications can perform non-I2S operations
before underflow (e.g. ``write`` method) or overflow (e.g. ``readinto`` method).
...
...
@@ -109,37 +109,37 @@ Methods
.. method:: I2S.init(sck, ...)
see Constructor for argument descriptions
.. method:: I2S.deinit()
Deinitialize the I2S bus
.. method:: I2S.readinto(buf)
Read audio samples into the buffer specified by ``buf``. ``buf`` must support the buffer protocol, such as bytearray or array.
"buf" byte ordering is little-endian. For Stereo format, left channel sample precedes right channel sample. For Mono format,
Read audio samples into the buffer specified by ``buf``. ``buf`` must support the buffer protocol, such as bytearray or array.
"buf" byte ordering is little-endian. For Stereo format, left channel sample precedes right channel sample. For Mono format,
the left channel sample data is used.
Returns number of bytes read
Returns number of bytes read
.. method:: I2S.write(buf)
Write audio samples contained in ``buf``. ``buf`` must support the buffer protocol, such as bytearray or array.
"buf" byte ordering is little-endian. For Stereo format, left channel sample precedes right channel sample. For Mono format,
"buf" byte ordering is little-endian. For Stereo format, left channel sample precedes right channel sample. For Mono format,
the sample data is written to both the right and left channels.
Returns number of bytes written
Returns number of bytes written
.. method:: I2S.irq(handler)
Set a callback. ``handler`` is called when ``buf`` is emptied (``write`` method) or becomes full (``readinto`` method).
Set a callback. ``handler`` is called when ``buf`` is emptied (``write`` method) or becomes full (``readinto`` method).
Setting a callback changes the ``write`` and ``readinto`` methods to non-blocking operation.
``handler`` is called in the context of the MicroPython scheduler.
.. staticmethod:: I2S.shift(*, buf, bits, shift)
bitwise shift of all samples contained in ``buf``. ``bits`` specifies sample size in bits. ``shift`` specifies the number of bits to shift each sample.
Positive for left shift, negative for right shift.
bitwise shift of all samples contained in ``buf``. ``bits`` specifies sample size in bits. ``shift`` specifies the number of bits to shift each sample.
Positive for left shift, negative for right shift.
Typically used for volume control. Each bit shift changes sample volume by 6dB.
@@ -47,7 +47,7 @@ Here, n keeps track of the current LED and every time the loop is executed we cy
One problem you might find is that if you stop the script and then start it again that the LEDs are stuck on from the previous run, ruining our carefully choreographed disco. We can fix this by turning all the LEDs off when we initialise the script and then using a try/finally block. When you press CTRL-C, MicroPython generates a VCPInterrupt exception. Exceptions normally mean something has gone wrong and you can use a try: command to "catch" an exception. In this case it is just the user interrupting the script, so we don't need to catch the error but just tell MicroPython what to do when we exit. The finally block does this, and we use it to make sure all the LEDs are off. The full code is::
Damien George <damien@micropython.org>