Photos of the setup and the GPS board and a sample terminal output would make this a trivial exercise to troubleshoot.
Without photos/board layouts to view and maybe eliminate RF noise and other transient sorts of things, I would guess you have a mismatch between the PC terminal and xbee speeds.
That really does appear to be a comms mismatch issue. You can see repeating patterns, but the chars are garbage. You also mention it updates about every second, which means the GPS is sending data and you are receiving it at the default 1Hz rate. I notice the HT has 8N1 on the bottom display. Maybe this has something to do with CRC/error correction on HT that’s not on the source signal from the xbee usb adapter?
Also, you should twist vcc/ground pairs together whenever running them any distance. The gps leads are probably too short to cause problems, but it’s a good habit to get into. Twist them together somewhat tightly and keep the pair away from your signal line.
One last test, switch your xbees. If the HT chars/patterns change, your xbees are talking at different speeds. If there’s no change, they are communicating properly but the problem exists on the GPS or computer side.
That schematic shows the same connection you have except it has 2 caps (10pF and .1pF I think) from vcc to ground at the xbee connection and what appears to be a voltage divider using resistors (only one showing). The caps wouldn’t be a bad idea to filter the RF, but the xbee’s caps should be good enough and your adapter shield probably already has them.
I keep going back to this being a comms mismatch. Try reprogramming xbees and gps to 9600. If the garbage chars are showing up at 1 sec intervals and the GPS communicates with HT with real data, the xbee to gps link must be mismatched as waltr mentioned earlier.
Ok, after some more tinckering and putting the gps out through a invertor it still didn’t work.
Then I wanted to reset everything but first I wanted to check the nmea output again of the gps with HT directly connected to the pc. All the data was gash …
I decided to reflash the mediatek again with the diydrones firmware. I also read somewhere that the specific protocol was called upon by the arducopter software and that the gps was default in NMEA.
Also the default bps was 38400.
I then rechecked with HT and the NMEA strings were coming in.
Reprogrammed the xbee’s to 38400 an behold … It works!!!
Finally.
Nevertheless thanks for the help.It started me thinking a lot.
Curious about the application… because the RF range of the XBee Pros without high gain antennas: is not a great deal more than the error in GPS location estimates!
I got arround testing the xbee pro’s 900 with standaard wire antenna’s in a build up area with the receiving station indoors and I would get about a 200m range. So If I would use high gain antenne at a height it would be greatly improved.
