FT230X data corruption issue

[lokkje <lokkjje@xxxxxxxxx>]

Hi everybody,

I have an application that's transferring large text files to and from an FT230X.  Using the VCP driver, I've managed to transfer the files without any issues, but when I use libFTDI I'll reliably see a few hundred bytes go missing (as in, not appear in the data stream, no warning or anything) around the same place every time (within a few lines radius); the place where bytes are dropped varies by file, but certain files will reproduce it consistently.

The application runs on OSX.  I've been debugging the receive half of communications: I've put debug prints in libusb_bulk_transfer to verify it receives bad data from the OS (or at least the libusb/darwin stuff), and I've scoped the UART pins on the other side of the FTDI chip to verify it's receiving good data.  Unfortunately I don't have a USB sniffer handy to check actual USB traffic.

My standard libFTDI setup is open_desc(), followed by usb_reset() and purge_buffers(), then setting line properties and baud rate and all of that.  Getting rid of usb_reset and purge_buffers doesn't affect anything.  This happens on 1.0, and it also happens with top-of-tree (which has a few new FT230X commits it looks like, though mostly relating to eeprom and the clocking bug).

Has anybody else run into this, or does anybody have ideas for further debugging?  I tried capturing the VCP's setup sequence using OSX's instrumented usb driver, but between the limitations of instrumentation and not having great docs on the FTDI protocol I didn't get very far...

Any help appreciated!  Thanks,

Tom

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