I have this old DeLorme Earthmate PN-40 Handheld GPS that I'm trying to use.
It has a proprietary data/charging connector, and the original cable is long since broken and gone.
DeLorme was purchased by Garmin, and Garmin really had no interest in supporting DeLorme's old products. I'm pretty sure they only wanted DeLorme because they have such awesome maps.
Anyway, you can't buy a new cable. They were never made by any third-party companies. They're also notoriously fragile. There are none available on eBay, unless you happen to find an entire GPS that includes one. You need the cable if you want to send software updates or up/download points, routes, and tracks.
The connector design is a decent concept. It consists of eight gold-plated pads. This is pretty good for a waterproof, outdoor device. Much better than the Micro USB connector that other GPS units seem to have: If the contacts get wet and filthy, you just wipe them off.
The weak points are all on the cable. First, it has a sucky strain relief that's too weak, and broken conductors are common as a result. The connector has tiny spring pins that are extremely susceptible to dirt and grime. Also, the spring inside the pins corrode if you get them wet, and they break or stick. Sometimes WD-40 will buy you a little more life, but there's no way to replace the spring pins or clean them out.
DeLorme used to be pretty awesome about replacing these cables for free, no questions asked. Garmin, not so much. Garmin, 12 years after this GPS came out on the market? Yeah, forget it.
And so begins my quest to make a data connector from scratch. I'll share what I learn here, to help out anyone else looking to do the same.