PC monitors two-way RS-232 transmission

Posted on Jan 14, 2013

The method in Figure 1a needs no access or knowledge of the communicating devices. A C program opens two COM ports and installs interrupt-service routines for IRQ4 and IRQ3. Upon the reception of an interrupt, the routine stores a byte in a common circular buffer with the COM identifier and error flags. The main program displays the contents of the buffer, indicating time intervals in milliseconds between consecutive transfers. Although the program simplifies the time measurement, it preserves the original byte order and correctly reflects time relationships as long as the main program keeps up with transmission speed.

If you need greater precision, you can easily modify the program to record time stamps, along with the data and status bytes, in the circular buffer. Unfortunately, not all PCs offer two COM ports. This deficiency is a common drawback of notebook compu

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