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i2c: avoid getting stuck due to adaptive clocking #413

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i2c: avoid getting stuck due to adaptive clocking #413

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38 changes: 26 additions & 12 deletions pyftdi/i2c.py
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Original file line number Diff line number Diff line change
Expand Up @@ -390,6 +390,7 @@ def __init__(self):
self._ck_idle = 0
self._read_optim = True
self._disable_3phase_clock = False
self._clkstrch = False

def set_retry_count(self, count: int) -> None:
"""Change the default retry count when a communication error occurs,
Expand Down Expand Up @@ -438,10 +439,10 @@ def configure(self, url: Union[str, UsbDevice],
else:
timings = self.I2C_1M
if 'clockstretching' in kwargs:
clkstrch = bool(kwargs['clockstretching'])
self._clkstrch = bool(kwargs['clockstretching'])
del kwargs['clockstretching']
else:
clkstrch = False
self._clkstrch = False
if 'direction' in kwargs:
io_dir = int(kwargs['direction'])
del kwargs['direction']
Expand Down Expand Up @@ -469,7 +470,7 @@ def configure(self, url: Union[str, UsbDevice],
ck_buf = self._compute_delay_cycles(timings.t_buf)
self._ck_idle = max(ck_su_sta, ck_buf)
self._ck_delay = ck_buf
if clkstrch:
if self._clkstrch:
self._i2c_mask = self.I2C_MASK_CS
else:
self._i2c_mask = self.I2C_MASK
Expand All @@ -489,7 +490,6 @@ def configure(self, url: Union[str, UsbDevice],
frequency = self._ftdi.open_mpsse_from_url(url, **kwargs)
self._frequency = (2.0*frequency)/3.0
self._tx_size, self._rx_size = self._ftdi.fifo_sizes
self._ftdi.enable_adaptive_clock(clkstrch)
if not self._disable_3phase_clock:
self._ftdi.enable_3phase_clock(True)
try:
Expand Down Expand Up @@ -880,7 +880,7 @@ def flush(self) -> None:
if not self.configured:
raise I2cIOError("FTDI controller not initialized")
with self._lock:
self._ftdi.write_data(self._immediate)
self._ftdi.write_data(bytearray(self._immediate))
self._ftdi.purge_buffers()

def read_gpio(self, with_output: bool = False) -> int:
Expand Down Expand Up @@ -1057,21 +1057,35 @@ def _send_check_ack(self, cmd: bytearray):
# read SDA (ack from slave)
cmd.extend(self._read_bit)
cmd.extend(self._immediate)
self._ftdi.write_data(cmd)
ack = self._ftdi.read_data_bytes(1, 4)
self._i2c_write_data(cmd)
ack = self._i2c_read_data_bytes(1, 4)
if not ack:
raise I2cIOError('No answer from FTDI')
if ack[0] & self.BIT0:
raise I2cNackError('NACK from slave')

def _i2c_write_data(self, cmd: bytearray):
if self._clkstrch:
cmd.insert(0, self._ftdi.ENABLE_CLK_ADAPTIVE)
cmd.append(self._ftdi.DISABLE_CLK_ADAPTIVE)
self._ftdi.write_data(cmd)

def _i2c_read_data_bytes(self, readlen: int, attempt: int = 1, request_gen=None) -> bytearray:
data = self._ftdi.read_data_bytes(readlen, attempt, request_gen)
if not data and self._clkstrch:
self.log.warning('bus seems wedged')
self._ftdi.purge_rx_buffer()
self._ftdi.write_data(bytearray((self._ftdi.DISABLE_CLK_ADAPTIVE,)))
return data

def _do_read(self, readlen: int) -> bytearray:
self.log.debug('- read %d byte(s)', readlen)
if not readlen:
# force a real read request on device, but discard any result
cmd = bytearray()
cmd.extend(self._immediate)
self._ftdi.write_data(cmd)
self._ftdi.read_data_bytes(0, 4)
self._i2c_write_data(cmd)
self._i2c_read_data_bytes(0, 4)
return bytearray()
if self._fake_tristate:
read_byte = (self._clk_lo_data_input +
Expand Down Expand Up @@ -1117,7 +1131,7 @@ def write_command_gen(length: int) -> bytearray:
return cmd_chunk

while rem:
buf = self._ftdi.read_data_bytes(rem, 4, write_command_gen)
buf = self._i2c_read_data_bytes(rem, 4, write_command_gen)
self.log.debug('- read %d bytes, rem: %d', len(buf), rem)
chunks.append(buf)
rem -= len(buf)
Expand All @@ -1136,8 +1150,8 @@ def write_command_gen(length: int) -> bytearray:
cmd.extend(read_not_last * (rem-1))
cmd.extend(read_last)
cmd.extend(self._immediate)
self._ftdi.write_data(cmd)
buf = self._ftdi.read_data_bytes(size, 4)
self._i2c_write_data(cmd)
buf = self._i2c_read_data_bytes(size, 4)
self.log.debug('- read %d byte(s): %s',
len(buf), hexlify(buf).decode())
chunks.append(buf)
Expand Down
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