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.

64 bit

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

Manufacture Chip set	PL2303HX PLUGABLE	FT232R TRONIX	FT232R CHIP-10X	TUSB3410
Picture
Where Purchased
COM Port	4	3	6	5
8/6/14 inc. VAT £ p+p	£11.59	£9.98	£19.18	£23.99

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, by sending data from one port to the other, changing each parameter settings and reporting the resultsresult of each test.

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 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.

I now have a correctly wired NULL MODEM Cable. Here are the results of 2 USB Serial Cable connected together.

Both FTDI Serial cables

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Keyspan & Prolific Serial cables

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Keyspan & FTDI Serial cables

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Com Port Stress Test

This program either tests COM Ports individually, or with 2 COM ports as above.

Dual USB Serial Cable Results

These results shows the test running at different baud rates with RTS and CTS enabled.

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

Both FTDI Serial cables

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This is not using any handshaking and has no errors

Keyspan & Prolific Serial cables

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This is using RTS and DTR, reports errors to start with and then is stable.

Keyspan & FTDI Serial cables

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This is using RTS and DTR, reports errors to start with and then is stable.

Prolific & FTDI Serial cables

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This is using RTS and DTR, reports errors to start with and then is stable.

Single USB Serial Cable Results

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

USB Serial Port (COM3) FTDI Results

There are no errors.

Keyspan USB Serial Port (COM5) Results

There are no errors.

USB Serial Port (COM6) FTDI Results

There are no errors.

09/06/2014 Test Results

Just to make sure that the test are the same I ran the same test on all 4 cables one after the other at the same speed.

There were no errors.

If I ran the Keyspan at a higher speed I would get a blue screen.

Keyspan

Tronix FTDI

CHIPI-X FTDI

Prolific

Conclusion

All cables pass the individual single speed test.

The dual serial port test still need to be run.

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.

We know that the Keyspan adapter works but if the FTDI adapter can be used instead, it is half the price.