floppyio – Read flux transition information into the buffer.
Available on these boards
- floppyio.flux_readinto(buffer: circuitpython_typing.WriteableBuffer, data: digitalio.DigitalInOut, index: digitalio.DigitalInOut, index_wait: float = 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.
- Parameters:
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
- Returns:
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
validitybuffer 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_maxandt3_maxare used to distinguish these pulses. A pulse withp <= t2_maxis a “T2” pulse, a pulse witht2_max < p <= t3_maxis a “T3” pulse, and a pulse witht3_max < pis 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
- Parameters:
buffer – Read data into this buffer. Byte length must be a multiple of 512.
flux – Flux data from a previous
flux_readintocallt2_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
1and previously valid sectors are not decoded.clear_validity – If
True, clear the validity information before decoding and attempt to decode all sectors.
- Returns:
The actual number of sectors read