Downloading data from my FURUNO GP-30 gave me no problems. But it took me long time to figure out why I coudn't upload waypoints and routes to the GP-30 via the serial port in my ThinkPad T30.
I tried nearly everything tested the cable, tested a lot of different software and even wrote a little c-program to communicate with the serial port. I also tried a serial-to-usb converter with no results. Then I stumbled over this RS232 Tutorial.
According to this - serial ports are not just serial port but can be divided into three general categories:
The types of driver ICs used in serial ports can be divided into three general categories:
* Drivers which require plus (+) and minus (-) voltage power supplies such as the 1488 series of interface integrated circuits. (Most desktop and tower PCs use this type of driver.)
* Low power drivers which require one +5 volt power supply. This type of driver has an internal charge pump for voltage conversion. (Many industrial microprocessor controls use this type of driver.)
* Low voltage (3.3 v) and low power drivers which meet the EIA-562 Standard. (Used on notebooks and laptops.)
Then I installed the waypoint upload software to my ten years old Compaq Presario and suddenly I could upload routes and waypoints but only via the on board serial port. The serial-to-usb converter didn't still work.
So if people experience no result trying to upload data to these old GP-30's from their notebooks and laptops. Then I think it could be a matter of these Low voltage ports not are able to provide the FURUNO device with enough voltage. See the above RS232 Tutorial.