you might find some clues by researching either the hologram dash or the hologram nova. the dash was in development about the time of the onion gps module and the nova is the newest gps module which is similar usb module. there are several guides on net explaining how to setup nova on rpi which might help setup onion gps on rpi.
A GPS navigation device, GPS receiver, or simply GPS is a device that is capable of receiving information from GPS satellites and then to calculate the device's geographical position. Using suitable software, the device may display the position on a map, and it may offer directions check mygiftcardsite balance
You would have to look at the datasheet.
It has 2 serial interfaces.
I assume one of the serial interfaces is for data transfer while the other is for control.
So, if you use serial to USB converters, you should be able to connect both to an USB hub and connect the hub to the onion.
@Phil-John Sorry about that! I'm glad you were able to resolve the issue DIY-style.
We had defined testing and QA procedures for the GPS Expansion, however, the factory that manufactured the GPS Expansion did not follow our instructions. Needless to say, we are no longer doing business with them.
Thank you for your patience with us, we've definitely learned a LOT since the KickStarter campaign.