I have a Dell 7040 small form factor system which has a port on the motherboard for a serial port, but I can’t find the right cable for it. I want to connect a GPS module with PPS and a real serial port is the best option.
The chip is a MAX3243C, which converts RS232 voltage levels to logic levels (probably 3.3V), so that shows that the port carries the serial signals. The serial port is part of the chipset, it’s not a USB add-on or something like that.
If I can get one of those cables I can most likely find the right signals on the PCB, de-solder the MAX3243C and tack some wires on there, and then connect a GPS receiver internally. Re-purpose the wifi antenna port for a GNSS antenna.
If you’re feeling adventurous, could you not simply solder direct to the pins and ignore the connector? They look pretty exposed.
And the GPS module almost certainly also uses TTL serial with a MAX232 or clone chip on the RS232 side. Bypass that and you can connect direct (assuming same TTL voltage level - most stuff is 3.3v these days)
I was thinking about that. It would be nice for it to be removable but 1mm pitch isn’t too bad to solder wires onto. Getting the pinout will have to be a bit of trial an error, but I only need the RX and CTS lines (for NMEA output and a PPS signal).
The GNSS module I have in mind was bought for use with an RPi so it’s 3.3V signalling. I’d mount it internally, hopefully it won’t get too much interference in there, with a pigtail going to an unused cut-out in the case for a WiFi antenna.
Back in the day I did a mod chip for a slim PS2. I think the pitch of the chips I was soldering too was 0.5mm, might have been 0.8mm. Anyway at that time I realized it’s not that bad.
You need a decent iron with a good, flat tip. Conical tips are stupid, I don’t know why they even exist. You need some good flux and solder, and patience. Kynar wire is good, or you can use magnet wire.
Honestly at this point 1mm pitch legs on a connector isn’t something I’d think twice about. The main worry is that being so near to other components it might be awkward to access.
You can buy the Dell part off eBay, but only from the US so it’s kinda expensive by the time it gets here. The other end of the cable has the same connector but at least I have a part number for the socket.