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spi: support read length > SpiController.PAYLOAD_MAX_LENGTH #254

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spi: support read length > SpiController.PAYLOAD_MAX_LENGTH #254

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da9bb30
spi: support read length > SpiController.PAYLOAD_MAX_LENGTH
buganini Jul 2, 2021
184dc66
SPI: don't read zero remainder in chunked reading
buganini Jul 4, 2021
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24 changes: 18 additions & 6 deletions pyftdi/spi.py
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Original file line number Diff line number Diff line change
Expand Up @@ -773,8 +773,6 @@ def _exchange_half_duplex(self, frequency: float,
raise SpiIOError("FTDI controller not initialized")
if len(out) > SpiController.PAYLOAD_MAX_LENGTH:
raise SpiIOError("Output payload is too large")
if readlen > SpiController.PAYLOAD_MAX_LENGTH:
raise SpiIOError("Input payload is too large")
if cpha:
# to enable CPHA, we need to use a workaround with FTDI device,
# that is enable 3-phase clocking (which is usually dedicated to
Expand Down Expand Up @@ -830,17 +828,31 @@ def _exchange_half_duplex(self, frequency: float,
cmd.extend(write_cmd)
if readlen:
if not droptail:
n = readlen // SpiController.PAYLOAD_MAX_LENGTH
r = readlen % SpiController.PAYLOAD_MAX_LENGTH

rcmd = (Ftdi.READ_BYTES_NVE_MSB if not cpol else
Ftdi.READ_BYTES_PVE_MSB)
read_cmd = spack('<BH', rcmd, readlen-1)
cmd.extend(read_cmd)
for i in range(n):
read_cmd = spack('<BH', rcmd, SpiController.PAYLOAD_MAX_LENGTH-1)
cmd.extend(read_cmd)
if r:
read_cmd = spack('<BH', rcmd, r-1)
cmd.extend(read_cmd)
else:
bytelen = readlen-1
if bytelen:
n = bytelen // SpiController.PAYLOAD_MAX_LENGTH
r = bytelen % SpiController.PAYLOAD_MAX_LENGTH

rcmd = (Ftdi.READ_BYTES_NVE_MSB if not cpol else
Ftdi.READ_BYTES_PVE_MSB)
read_cmd = spack('<BH', rcmd, bytelen-1)
cmd.extend(read_cmd)
for i in range(n):
read_cmd = spack('<BH', rcmd, SpiController.PAYLOAD_MAX_LENGTH-1)
cmd.extend(read_cmd)
if r:
read_cmd = spack('<BH', rcmd, r-1)
cmd.extend(read_cmd)
rcmd = (Ftdi.READ_BITS_NVE_MSB if not cpol else
Ftdi.READ_BITS_PVE_MSB)
read_cmd = spack('<BB', rcmd, 7-droptail)
Expand Down