Re: FTDI UM245R FIFO-USB interface
- From: Ben Jackson <ben@xxxxxxx>
- Date: Wed, 01 Jul 2009 18:05:50 GMT
On 2009-07-01, Jeroen Belleman <jeroen@xxxxxxxxxxxxx> wrote:
I'm trying to use an FTDI UM245R USB-FIFO module to read
I pump data into the FIFO at a rate of one byte every 192us
whenever there's room for it, as signalled by the /TXE flag.
I haven't used the 245 but I have used the 232R in a similar app. My
conclusion was that FTDI never intended these parts to be used to read
bulk data like this. I was using the parallel mode of the 232 with
FTDI's own library and like you I could interact with the chip's fifo
just fine but I was still losing data. Turns out that the FTDI driver
itself was periodically reading and discarding data (via a thread it
would create when you opened the device). My program was slowed down
printing more and more debug and losing more and more data but worked
if I turned off all debug. I ended up driving it from a linux box with
an open source FTDI library.
I don't know if a serial mode (such as you must be in for ttyUSB0 to
work) suffers from the same problem, but I wouldn't be surprised to
find it's hard to get it to work.
--
Ben Jackson AD7GD
<ben@xxxxxxx>
http://www.ben.com/
.
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