Real time serial control from NT


Thread Starter

Mark Nicholls

Currently using NT as a automation platform but I need to be able to do 'frame accurate' serial communications. The PC gets an external clock signal via serial line and then the application layer needs to be able to instruct some sort of driver to output a serial command string at a given time. Clearly the input of the time signal and the output of the serial strings are not deterministic under NT.

I have looked at RTX extensions and this seems possible, though probably overkill for doing something seemingly relatively straightforward.

It would be nice to have an easier solution.
You may want to look into a communication technique using shared memory. SCRAMNet is a Real-Time Communication concept that is truely deterministic and has very low latency. It is mostly used in military and aircraft simulators were the frame rates and timeing is critical. It is also used in controlling steel micro mills, high speed assembly, and power plants.

Data is written to memory on the NIC and automatically sent to all nodes so that all the PCs will see the same data within microseconds.

Info on SCRAMNet can be found on website

Study the microsoft knowledgebase and or SDK on how to write a VXD. THe VXD will sit below the application ring and allow you to access the crs232 comm API via a simpler private protocol. Of course, you can buy and install an rs232 VXD from 3rd party(cheapest for small quantity) or

Akumeka Technology

Mark Nicholls

This seems very interesting, OK so I write a VXD driver, but does this get past my latency problem ? I still can't lock out interupts ? or can I ?

Mark Nicholls

The IO format is determined by third parties and is generally RS232, RS422, I had a look at systran, I think that is doing something different and far more complex.

Anand Hebbal

Hi, there are drivers available for Win NT by B&R automation. U can find more info on it by visiting The driver is called PVI(process visulisation Interface). It gives u real time control. The most common application interface is VB on RS485,RS232 & even CAN