Clock stretching issue

[jimsyt]

When I try to use clock stretching, even with a device that doesn't clock stretch, the second read always fails, but if I repeat the "i2c.configure" command after every read, it works fine. Any idea what I might be doing wrong?
Thanks.

Example:
python
Python 3.10.12 (main, Nov 6 2024, 20:22:13) [GCC 11.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.

import pyftdi
from pyftdi.i2c import I2cController
i2c = I2cController()
i2c.configure('ftdi://ftdi:2232h/2', frequency=100000, clockstretching=True)
slave = i2c.get_port(0x48)
data = slave.read_from(0x0, 2, relax=True, start=True)
print(data)
bytearray(b'\x16\xe0')
data = slave.read_from(0x0, 2, relax=True, start=True)
Traceback (most recent call last):
File "", line 1, in
File "/home/jsytniak/.local/lib/python3.10/site-packages/pyftdi/i2c.py", line 121, in read_from
return self._controller.exchange(
File "/home/jsytniak/.local/lib/python3.10/site-packages/pyftdi/i2c.py", line 773, in exchange
self._do_prolog(i2caddress)
File "/home/jsytniak/.local/lib/python3.10/site-packages/pyftdi/i2c.py", line 1029, in _do_prolog
self._send_check_ack(cmd)
File "/home/jsytniak/.local/lib/python3.10/site-packages/pyftdi/i2c.py", line 1060, in _send_check_ack
raise I2cIOError('No answer from FTDI')
pyftdi.i2c.I2cIOError: No answer from FTDI
i2c.configure('ftdi://ftdi:2232h/2', frequency=100000, clockstretching=True)
data = slave.read_from(0x0, 2, relax=True, start=True)
i2c.configure('ftdi://ftdi:2232h/2', frequency=100000, clockstretching=True)
data = slave.read_from(0x0, 2, relax=True, start=True)
i2c.configure('ftdi://ftdi:2232h/2', frequency=100000, clockstretching=True)
data = slave.read_from(0x0, 2, relax=True, start=True)
i2c.configure('ftdi://ftdi:2232h/2', frequency=100000, clockstretching=True)
data = slave.read_from(0x0, 2, relax=True, start=True)
print(data)
bytearray(b'\x17 ')
data = slave.read_from(0x0, 2, relax=True, start=True)
Traceback (most recent call last):
File "", line 1, in
File "/home/jsytniak/.local/lib/python3.10/site-packages/pyftdi/i2c.py", line 121, in read_from
return self._controller.exchange(
File "/home/jsytniak/.local/lib/python3.10/site-packages/pyftdi/i2c.py", line 773, in exchange
self._do_prolog(i2caddress)
File "/home/jsytniak/.local/lib/python3.10/site-packages/pyftdi/i2c.py", line 1029, in _do_prolog
self._send_check_ack(cmd)
File "/home/jsytniak/.local/lib/python3.10/site-packages/pyftdi/i2c.py", line 1060, in _send_check_ack
raise I2cIOError('No answer from FTDI')
pyftdi.i2c.I2cIOError: No answer from FTDI

[jimsyt]

I should add that I'm using a FT2232H mini-module with version 0.55.4 of pyftdi. the first transfer looks correct on my oscope. The second command that fails doesn't trigger my oscope at all. I'm going to connect an analyzer next and see if it sees anything wrong.I'm using the circuit described here - https://electronics.stackexchange.com/questions/651655/ft232h-clock-stretching-using-mpsse