RS-485 Serial Communication

The following pictures show some SuperCom specific timings ("direction" switch latency) with the RS-485 controlled through the onboard COM1 and through serial ports on a multiport PCI card.

The data monitor used was capturing data on a Notebook and was not involved in data communications.

The captured data packet was 82 bytes long ("A012345....B").

The last event shows only the RTS signal dropping.


OnBoard COM1

it took 0.36ms* = 360 µs (micro seconds)


Serial ports on a PCI card

it took 0.45ms* = 450 µs (micro seconds)

*Direction switch latency was on the above tests constantly less than 1 ms.

The switch latency in SuperCom is also related to the transmission speed (bps). We measured a latency of about 3.50ms when transmitting with 2400 bps, about 1.20ms with 9600bps and below 1 ms when higher than 9600bps. The type of serial port, the number of open serial ports and running on a busy server may have affect on the result.

The RS-485 support, in SuperCom, is easily activated by setting the ComType or by a function call.

Please also ask for the 'SuperCom Technical Library -- RS-485 and 9-Bit Multidrop Communications Paper'.

The DEMO software found online, even when activating RS-485, are working with limited functionality, especially when it comes to response timing. The complete functionality is contained only in the licensed version.

Modified at: