floppyio – Read flux transition information into the buffer.

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floppyio.flux_readinto(buffer: circuitpython_typing.WriteableBuffer, data: digitalio.DigitalInOut, index: digitalio.DigitalInOut, index_wait=0.22) int

The function returns when the buffer has filled, or when the index input indicates that one full revolution of data has been recorded. Due to technical limitations, this process may not be interruptible by KeyboardInterrupt.

  • buffer – Read data into this buffer. Each element represents the time between successive zero-to-one transitions.

  • data – Pin on which the flux data appears

  • index – Pin on which the index pulse appears

  • index_wait – Time to wait, in seconds, for the index pulse


The actual number of bytes of read

floppyio.mfm_readinto(buffer: circuitpython_typing.WriteableBuffer, flux: circuitpython_typing.ReadableBuffer, flux_t2_max: int, flux_t3_max: int, validity: bytearray | None = None, clear_validity: bool = True) int

Decode MFM flux into the buffer

The track is assumed to consist of 512-byte sectors.

The function returns the number of sectors successfully read. In addition, it updates the validity buffer with information about which sectors were read.

MFM encoding uses pulses of 3 widths, “T2”, “T3” and “T4”. A 1440KiB disk in standard MFM format has “T2” pulses of 2000ns, “T3” pulses of 3000ns, and “T4” pulses of 4000ns.

Parameters t2_max and t3_max are used to distinguish these pulses. A pulse with p <= t2_max is a “T2” pulse, a pulse with t2_max < p <= t3_max is a “T3” pulse, and a pulse with t3_max < p is a “T4” pulse.

The following code can convert a number in nanoseconds to a number of samples for a given sample rate:

   def ns_to_count(ns, samplerate):
       return round(ns * samplerate * 1e-9)

This means the following typical values are a good starting place for a 1.44MB floppy:
t2_max = ns_to_count(2500, samplerate) # Mid way between T2 and T3 length
t3_max = ns_to_count(3500, samplerate) # Mid way between T2 and T3 length
  • buffer – Read data into this buffer. Byte length must be a multiple of 512.

  • flux – Flux data from a previous flux_readinto call

  • t2_max – Maximum time of a flux cell in counts.

  • t3_max – Nominal time of a flux cell in counts.

  • validity – Optional bytearray. For each sector successfully read, the corresponding validity entry is set to 1 and previously valid sectors are not decoded.

  • clear_validity – If True, clear the validity information before decoding and attempt to decode all sectors.


The actual number of sectors read

floppyio.samplerate: int

The approximate sample rate in Hz used by flux_readinto.