Ultimate Helper GPS Adapter

I'm a big fan of the Adafruit Ultimate GPS. It has pulse-per-second support, supports 5V and 3.3V, and both includes a ceramic antenna and has support for an external active antenna. But, it's useless outside of a breadboard. So I made this.

What's it do?

This base for the Ultimate GPS adds what I most often wanted: more LEDs, USB, and DB9. First, supplementing the Fix LED on the GPS itself I added a PPS LED, a power LED, and two LEDs for receive and transmit. Next I added an expensive USB chipset (FTDI232RL from Digikey or Mouser) and mini-B connector so you can plug the board into your laptop and watch the NMEA stream or power it standalone from USB. Finally, there's a TTL-to-Serial adapter (MAX232 or SP232) with PPS on the DCD line via a Schmitt trigger inverter (SN74LVC1G14) so you can plug it into a motherboard with a real serial port and use this adapter as a reference time source for NTP with the PPS+NMEA driver.

That's cool, what else?

The GPS module sits above the adapter board and inserts into female headers, it stacks well. And the board isn't just resting on your table top, there's 6mm standoffs with M3 screws to raise it up a little.

Neat. And the options?

I expect many people already have an Ultimate GPS v3 from Adafruit just sitting around, so I hope this board makes it more usable. But for those who don't, I can ship a compatible GPS assembled. And for the two of you without an extra USB Mini-B cable, I can ship that too, send me a note requesting it.

As to the GPS options, there's now two choices: One is built with a PA6H module, which provide GPS and support for an external antenna. I drop in the u.FL to SMA adapter, but do not include an antenna. (But I have a couple extra Taoglass antennas, send a message if you don't want to buy your own from Mouser.) The other module uses a GMS-G6 which tracks both American GPS and Russian GLONASS so you have double the satellites to find. However, it doesn't support an external antenna. Despite that, they still work great indoors.

Driver support?

MacOS has had FTDI support built-in since OS 10.9 or so. And the official FTDI drivers work on my antique Vista laptop. I went with the FT232 instead of much cheaper PL2303 or CHP340/341 just to make it a little easier for everyone that has to use this board.

How do I use it with NTP?

I have this in my ntp.conf:

server 127.127.20.1 prefer mode 18 minpoll 3
fudge 127.127.20.1 flag1 1 flag3 1 refid PA6H

And this in my devfs.conf (FreeBSD)

link  cuau0 pps1
link  cuau0 gpspps1
link  cuaU0 gps1

pps1 is used by driver 22, gpspps1 and gps1 are used by driver 20. cuau0 is my hardware serial port, and cuaU0 is the first USB serial device. But don't blindly copy that, read the NTP documentation about the "flags" and "mode" to understand what's happening.

Cool.

Yeah. I think so. I hope you enjoy it.