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I cannot get the radio to talk to the computer

The most likely problem areas are 

1) the COM port number is not correct. See below for using CommTest to determine the correct Com port number and here for changing the COM port setup.

2) there is a cabling problem between the receiver and computer. See here for cable type.

3) you are running a PDA hotsync program that has acquired all of the COM ports

Using CommTest

CommTest is a free program to help with checking communication between the radio and the PC. It is available on the Download page of the author's web site. This screenshot shows the communication from a radio after power on. In this instance Com 4 and Com 7 are present on the PC. Note that the last message shows that the radio is connected to Com 7. 

USB attached devices

If the programming cable or USB/serial adapter uses a Prolific chip then please contact the author who has 'known to work' drivers for Windows XP, Vista and Windows 7.

Be aware that these USB to serial adapters and programming cables that plug directly into a USB port will be assigned a different Com port number by the operating system for each USB socket that you plug into. You will have to change the Com port number in the program if you use a different USB socket otherwise you will get an error when trying to read/write the radio.

To determine the correct Com port number do the following:

1. with the USB cable/adapter NOT plugged into the PC run CommTest and take note of the ports that are shown in green.
2. stop CommTest, plug in the USB cable/adapter and run CommTest again. The extra port shown in green is the port that has been assigned to the cable. Use this port number in the program. If no extra port is shown then you probably need to install drivers for the USB cable/adapter.

An alternative way to determine the port number is to plug the USB cable/adapter into the PC and then use the Windows Device Manager. Look at the section Ports (COM and LPT) to see if your device is listed. If it is not listed look for any other entry in the list of devices with a yellow question mark (?) next to it showing as an unknown device. Remove the cable and see if the unknown device disappears. If it does then you need to install drivers for it to be recognised by the operating system.

Serial ports

Occasionally you will find that the serial port you are using does not comply with the RS232 spec regarding voltage levels. This is most likely to be found with laptop computers. Whether this is an issue for you depends on the level converter you are using, and whether or not you are attempting to power the converter from the serial port. 

Using a 10K resistor across the meter leads to provide a load, check the voltage between pin 3 (TX) and the casing of the comm port connector. You should have at least -7V (negative with respect to the casing). If you don't use the loading resistor the voltage should be at least -8V.

If your serial port does not pass the above test and you do have problems communicating with the radio then you can try using a USB/serial port adapter. But still do the voltage test because not all adapters are equal.

Level converters that directly attach to the USB port of your PC are powered from the USB port.