Hi mav, On 05/31/2013 08:54 PM, mav wrote: > Not yet, testing on a PC is my next plan. The hardware may not be > providing required processing power, but so far I can't conclude so. > It may get clarified by executing the test on a PC setup. > > The modem communicates well if FTDI chip and its corresponding USB > chain is bypassed. When FTDI and USB are brought in, the serial lines > sporadically gets 2 unwanted bytes which corrupts the data stream. The > two erroneous bytes are always printed as 2` which if mapped to the > FTDI Status Bytes will translate to [0011 0010 0110 0000]; this > indicates THRE, BI and OE bits are set. > > The same 2 bytes are also seen on the second FTDI chip which is left > to run at the chip's default latency (16ms) and is running slower > @19200 baud (the first line is @115200 baud). I suspect the erroneous > bytes are coming from the underlying USB libraries, and I am still > looking for ways to confirm this.
take a look at the ftdi_read_xxx() functions: The status bytes are sent with every incoming usb packet of the read request and then filtered by the code. May be the filtering has a bug or the status bytes appear at an unexpected position. I would start by adding raw logging of the data to disc and then examine it, may be create a new file for every incoming packet so it's nicely partitioned. Thomas -- libftdi - see http://www.intra2net.com/en/developer/libftdi for details. To unsubscribe send a mail to [email protected]
