RS-422 Interface programming
 

Hello,
I would like to write a program in linux to control five proffesional Video Tape Recorders. Can I connect a proffesional (dedicated) controller, 'copy' it's actions and put them all in a program, to control the VTRs?
No video is going in to the PC, just commands to the VCRs.
PC Linear editors cost about 15K, so i try to make the proccess cheaper.

Thank you.

You need a RS-232 to RS422 converter. RS-422 is an electrical specification. Hopefully the tape recorder manual will detail the communication protocol and all you need to do is write a program to output the comands via a com port.

If you do not have any details on the communication protocol you could connect the controller to a PCs com port via the RS-232 to RS-422 converter and record the "key strokes".

That's exactly what i need! can you explain the proccess, can it be done simply?
Can I record the actions, and build a simple software that 'plays' the recorded code to the VTR i choose?

To record the actions you need to build a "T" cable that splits the signals to the RS-232 to RS-422 converter. You didn't say if the recorder manual has any details on the communication protocol or the interface. If you do not know the pin-outs of the connector then it might take some work to figure it out. RS-422 uses 4 wires. A twisted pair for the transmit and a twisted pair for the receive. The twisted pair is a differential i.e. polarity + and - signal. The converter will probably not work if the + and - signals are reversed. It would be nice to split the RS-232 receive and transmit signal into two connectors. That way you can monitor both receive and transmit in case the controller requires some kind of response from the recorder.

You can use any terminal program to view. Hopefully the protocol uses straight ASCII characters. If not, you need to save the data and view it via a hex editor.