Introduction

Ever since computers were invented, the ability to communicate with them was paramount. The RS 232 serial port became the standard way to do this. Modern computers now use USB ports to communicate together be it a camera, mobile phone or a hard disk drive.

There are programs on the internet that test Serial Ports. The object of this section is to use these programs to test the different USB Serial cables that are candidates to use with Eazylink2.

Software

The following windows software was downloaded. 

Hardware

The following items were made

Name	Item	Circuit	Function
Loopback Connector			To test individual Serial Port
NULL MODEM adapter			To connect two Serial Ports together

Tested USB Serial Cables

4 cables are tested. These are:-

PL2303HX PLUGABLE	FT232R TRONIX	FT232R CHIP-10X	TUSB3410

Test & Results

Run as administrator
	It was found that unless these programs were "Run as administrator," errors and a Blue Screen Of Death were encountered.

PL-2303 - Cable Test Program Ver 2.2.1.1

This program tests two serial ports connected together by a NULL MODEM cable, by sending data from one port to the other, changing parameter settings and reporting the results.

This screen shot shows a successful test provided that the Check Signal Events was un-ticked.

The RTS Signal testing ... section failed. This was due to the NULL MODEM cable was a 3 wire type. This only connects the data pins together. At least it shows that this program reports errors correctly.

This test will be run again with a fully connected NULL MODEM adapter.

Com Port Stress Test

This program either tests serial COM Ports individually , using the a Loopback connector, or with 2 COM ports as above.

If the COM port is faulty, error messages are generated and recorded into a log file. The following screen shot shows COM3 and COM4 connected together with the 3 wire NULL MODEM with RTS CTS selected randomly. As expected, error messages, like the result above were generated.

These tests will be repeated when I have the correct NULL MODEM Adapter.

Single USB Serial Cable Results

USB Serial Port (COM3) FTDI Results

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This test shows this These results shows the test running at 38400 baud with RTS and CTS enabled. There are different values in the port settings. This has had no effect on the speed of transfer. 

USB Serial Port (COM3) FTDI Results

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There are no errors.

Keyspan USB Serial Port (COM5) Results

This test shows this test running at 38400 baud with RTS and CTS enabled. There are different values in the port settings. This has no effect on the speed of transfer. There are no errors.

USB Serial Port (COM6) FTDI Results

This test shows this test running at 38400 baud with RTS and CTS enabled. There are different values in the port settings. This has no effect on the speed of transfer. There are no errors.

Prolific USB-to-Serial Comms Port (COM4) Results

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Conclusion

Initial tests look promising. Both FTDI cables and the Keyspan pass the individual test.

The Prolific one didn't pass the test when connected to another USB Serial Cable, but this could be due to the incorrect NULL MODEM being used.