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
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