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Tips and questions relating to the GPS modules from SFE
By NukWaste
Has anyone had any luck at all with the second serial port on the EB-85A GPS module?

I can use the primary serial all day long but the second serial port is a mystery to me.
I'm currently working on a project that is using the EB-85A GPS unit and here is the response I received when I last contacted the vendor about the second UART:
2nd UART is available, but It works when the WAAS or DGPS is connected. So this is why you never get any serial data from 2nd UART.
The answer is pretty cryptic, but from what I gather from their statement is that you need to tell the GPS unit to enable WAAS usage and once it gets a DGPS lock then second UART will output DGPS related information. I'm not sure if the second UART will provide the same information along with DGPS data that is on the first UART or not. I have a feeling it won't.

I personally have yet to be able to get the second UART to output any data, but then again I am playing around with the EB-85A indoors for right now, so DGPS could possibly simply just does not work indoors. :)

The following is commands that need to be given to the GPS unit in order for it to use DGPS I believe:

Set DGPS correction data source:

The following are available for mode:
0 – No DGPS source
1 – RTCM
2 – WAAS


Enable/Disable SBAS satellite usage:

Mode has only these two values:
0 – Disabled
1 – Enabled


I think you will have to set the DGPS source to WAAS and then enable SBAS. Maybe SBAS has nothing to do with DGPS, who knows. After playing around with those settings and the GPS unit does in fact go into a DGPS mode of some sort you'll get data pumping out of the second UART. Well good luck and enjoy! :)
By NukWaste
Thank you for responding. I try it.
By corvette123
when etek was making these modules, the 2nd port for DGPS wasnt working in the current firmware 1.8xseomthing......

however it can be used to receive RTCM updates if you set it to that!!!

not sure what would come out of the port in WAAS mode (if anything)....

remember DGPS RECEIVES RTCM information... so yah youd need a DGPS receiver to get those beacon signals and send it to the 2nd serial port.

however in some cases WAAS is more accurate than DGPS!

just use WAAS if you got it. and leave the 2nd port alone.\

what cases?

the distance you are from the DGPS transmitter / beacon... it does matter!!! accuracy affects that.

and DGPS RTCM beacons / and transmitters arent located everywhere.. in the US the coast guard runs them along the coast for naval use.... some other systems are into play.

but you need a separate receiver to receive and decode those transmissions.

i suggest you do a google search for DGPS and read up on the topic and see if DGPS is even available in your area.

you are better off using WAAS.

i dont know the current status of sannav's tinkering with the firmware or if they have it fixed, but last i heard the DGPS RTCM updates werent working.

anyways in 2 years when L1C and L2C satellites are launched and the GPS system is updated we will all have 4 inch accuracy.



yah pretty scary huh.

its coming.

:D :D :D