Non-standard Baud rate

[kgoez]

Does anyone know of a way to read information coming into a comm port at a non-standard baud rate, specifically 20833.333 baud? I've downloaded a few of the suggested programs, including comport toolkit. However, it does not seem to function properly at the non-standard rate.


Any suggestions?

 

[nbucska]

I assume you want to use a PC to read.
You can't read it using COM-port for
the clock frequency the PC uses is not divisible
with your baudrate but
1.) You could build a special hardware and write
some software to it
2.) Under some condition you could use the parallel
port as input and emulate the UART in software only
3.) Or you could modify an off the shelf interface card

I would have to know more about the problem to go into more
details.
<nbucska@pcperipherals.com>

 

[chippy99]

I think the problem is at the other end. What uses a baud rate of 20833.333 baud ?

 

[ielivaz]

I ssume you are using asynchronous communication and 8-bit bytes with one start and one or more stop bits.

A rate of 20833.333 b/s gives a 48 uSec time periord for a bit.

nearest standard rate is 19200 b/s wich gives a 52.08333 uSec time period.

the shifting after 9 bits (Start bit + 8-bit data) will be 36.75 uSec, because the oscilator could drift under or upper frecuecy by a +/- 1%, so under favaorable circunstances (oscilator dont drift down) you could read the data using 19200 baud rate.

 

[UruWay]

I have a similar problem, I need read and write data with a PC and an tranfer baud rate of 49.462 bauds.
I knowk that this is imposible with a common pc serial port because the cristal clock port is 1,8432 Mhz and my decimal divisor exactly 2,329043 ~ 2 to get 57600 baud.
I just need to evaluate this option:
1.) You could build a special hardware and write
some software to it >>> knowk some one? maybe a pic?
2.) Under some condition you could use the parallel
port as input and emulate the UART in software only >>> it´s really possible at this baud rate.
3.) Or you could modify an off the shelf interface card >>> not apply to my case.

Best Regards

 

[kgoez]

I think i may have found a solution for my problem. I have found a USB device which supposedly supports any baud rate in a range from 184bps to 1Mbps. I am currently waiting to recieve it. I needed the 485 version for my specific application, but they offer a 232 version also. Here is the link:

http://www.amplicon.co.uk/data/usb232h.html

Ill post if the device works for my project.