RS 422 serial with a multifunction DAQ Board PCI NI 6251 ?...

[gritche]

Hello !

I know I may prove to be a bit of an Heretic, but I would like to setup a RS 422-type connection between my NI 6251 and a absolute encoder ATM90. I know I can purchase a RS232 to RS422 converter to attach at the RS232 serial output of my computer. It will block my only available serial output. As I only need to perform the READ POSITION function on the device, I was wondering if an example was available somewhere.

Thank you

nicolas Ginet

[Ben]

I have heard of an example that runs on a FPGA that does I2C but not serial.

There is a lot of functionality built into serial that would have to be coded explitly. Examples that come to mind are,

Over-sampling - ASICs capable of handling serial comm typically over-smaple at about 10X the bits cell time.

Framing - distingishing between start-stop bits and the data.

Parity checking - computing and checking the parity.

So this seems less a question of heresy but rather of re-inventing the wheel. At the rate I charge my customer, I would have to be able to write the "pseudo-serial" function in less than 20 minutes for it to be worth their money to pay me to do so.

I'd like to urge you to spring for the serial adapter and save yourself a lot of work and head-aches (everytime you have a com issue, you will have to question your psuedo-serial code).

Trying to help,

Ben

[gritche]

I am a biologist and a self-taught Labview user and sometimes I misjudge my true capabilities !!!! You are right with reinventing the wheel, and I have decided for a simple USB to RS 485 cable from our beloved National Instruments to solve my connection problem.

Thank you !

Nicolas GINET