simple rs422 to rs232 conversion.

[jimseng]

Hi all.
This isn't strictly a picbasic question but there are so many helpful people on here I thought I would ask.
I have a databox on a boat outputting nmea sentences about wind speed/direction etc. My reading up on it is that it should be RS422 protocol and there are some instruments wired on this data bus. (Here is the manual if anybody needs it: http://www.stowemarine.com/archive/d...%20databox.pdf)
Anyway. I have read that RS422 can be directly connected to RS232 in most circumstances. This particular system appears not to be a differential circuit so I guess you could argue that it isn't in fact RS422.
Anyway. I was hoping to connect it to a USB to Serial converter and then to my laptop to read the data coming out of it. I have an opto isolator and wondered I can drive it directly from the Data out/Data ground from the data box and what I do with the opto output connecting to the usb to serial. I certainly don't want to damage the existing data box, I don't care about the usb to serial converter.
This is the wiring table for the data output on the data box:

Red +12V

Black 0V

Green Data Gnd

White Data Out

Brown Data In

Any thoughts?

[Ramius]

Hi Jimseng,
There are several commercially built converters if you do a google search for RS-422 to RS-232. Once you have RS-232 on a 9-pin connector, there is a TU-S9 9 pin to usb converter. Best, Ed

[Charlie]

I found this first try on a Google search...
http://www.takelog.com/images/rs232422.gif