Is there a way to readout continuously or force-flush the RX fifo of FTDI FT232R. I want to timestamp the received bytes and therefore want to avoid that the received bytes are being sent in chunks. I want to force the chip to sent them via USB as they arrive.
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Answer
FT232R
AFAIK, it is impossible for FT232R.
One can force to send data before the internal buffers is filled up but not in “number of bytes” basis. One can just lower data transmission latency timer from default 16 ms down to 1 ms.
See also my answer for “My board design with a FTDI chip is a lot slower than…”
FT2232D
FT2232D has SI/WU pin (send immediate/wake up), see DS, page 31. (FT2232H also has the SIWU pins but they don’t work in RS232 mode).
During normal operation (PWREN# = 0), if this pin is strobed low any data in the device TX buffer will be sent out over USB on the next Bulk-IN request from the drivers regardless of the pending packet size.
Unfortunately, I never used this pin so I can’t provide more details.