non-standard baud on Mac

[rvest]

Hello,

I am trying to configure a USB-serial adapter for communications with a Stanford Research Systems residual gas analyzer (RGA) on a Mac (10.6, Intel processor). The RGA device is hardwired for a baud rate of 28800; it can't be changed. Apparently the only serial driver API available on MacOS X is POSIX, which does not support 28800. Even though VISA can support arbitrary baud rates, the underlying driver can not, and VISA returns an error when you try to configure the port. this behavior is true for both LV8.5 and LV2009.

There are terminal emulator programs (e.g. ZTerm) that can configure the serial port and talk to my RGA. I guess they bypass the POSIX drivers somehow. Does anyone know of a way to get the 28800 baud capability through LabVIEW? I would like to integrate residual gas analysis into the beamline control system, which is LV-based.

Thanks for any help you can offer.

-Rob

[Coq_Rouge]

In the older days the UARTs used to have a 1843200 Hz crystal. This gave a max bit rate equal to 115200 bit pr second. But also bit rates equal to (115200/(whole number) ) was possible. So 28800 is what I will name a standard bitrate. I find somewhat strange that this bit rate is not supported. But a quick googling of POSIX+28800 gave some indications that the POSIX driver do not support this bit rate for some reasons. I do not know why.

[rvest]

I agree, 28800 should be standard for the reason you mention and because it was in widespread use at one time. I remember when a 28.8kbps modem was a blazing fast internet connection. Now, apparently, a 28.8 kbps modem is so obsolete you can't talk to it.