Sending bits via RS232

[Mark]

Is it possible to send bits via the RS232 port using v6.1?

[Chris_Rake]

Depends on what exactly you're trying to do. Serial (UART) comminucation involves a start bit, followed by a word (5-8, sometimes 9 bits long), followed by parity (if enabled), followed by a stop bit. This happens for every word of data transmitted. Thus the shortest sequence would be 7 bits long (start, 5 data bits, stop). The concept of sending a single bit simply does not exist.

However, the modem lines (DTR and RTS) can be toggled such that a simple waveform can be created - though the timing is not gaurenteed.

All of the above is true for UART communication in general as well as NI-VISA under LabVIEW.

[Paul Rocca]

Chris Rake wrote in message
news:506500000005000000EA7A0000-1021771306000@exchange.ni.com...
> Depends on what exactly you're trying to do. Serial (UART)
> comminucation involves a start bit, followed by a word (5-8, sometimes
> 9 bits long), followed by parity (if enabled), followed by a stop bit.
> This happens for every word of data transmitted. Thus the shortest
> sequence would be 7 bits long (start, 5 data bits, stop). The concept
> of sending a single bit simply does not exist.

It can exist if you are using sync RS232, as there are no start/stop bits,
we talk to radars and other kit using some very strange protocols (13
&17 bit words and other horrible things).

However you cannot do sync RS232 via std PC com port.

You would need to use something like an Emulex or Microgate WAN card
(they are both just jazzy RS232 cards) or a NI DIO-32HS with level shifters.

NI used to do a serial protocol analyser card which you could use for this
sort of thing, chat to you local NI rep about it.

All depends what you want to use it for, we do a lot of sync RS232 stuff,
give me a mail if you have any questions.

Paul

Dr Paul Rocca - Managing Director
Brill Engineering Ltd, 3 Longwood Court,
Love Lane, Cirencester, Gloucestershire
GL7 1YG. www.brill-eng.co.uk
Phone: 01285 883888 Fax: 01285 883876

NI Alliance Member Since 1992

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