Hi there all.
(This problem is on APM1 2560)
2 days ago I was merrily aduplaning around doing some PID tuning and all was well. Brought the aircraft in for a smooth landing and called it quits for the day. The very next day went for a drive down south to do some more tuning, fired up the telemetry and noticed No GPS lock on the planner screen. No dramas i thought... i'll just check the light on the gps(mediatek)... it was solid. Weird. So I tried every reset type and still no joy. Still a solid light on the gps but no fix on the planner. Called it quits for the day and just did some manual flight. Came home and decided to connect via USB. More problems.. now I can connect via USB only as the ardupilot is rebooting/initialising. If I wait till eveything initialises i can no longer connect. I get the message serial link isn't fast enough. (please see the attached picture). What makes it even more weird is that if I swap back to Ublox I can connect whenever I want (booting or well initialised) and get a gps fix within 2 mins (whilst sitting by the window). To make things even more confusing..... when using the Ublox the HUD is pitching up and down slightly +/- 10°. Talk about a frustrating couple of days!
Any ideas anyone... maybe a troubleshooting method? By brain hurts!
Ah rite. Tried scoping the GPS serial lines to see if there is something being sent? If there is try and scope the track on APM to make sure there is an electrical connection, not a broken pin or something. Failing that sounds like some dodgy code...which is odd
Finally managed to find a spare mediatek.....
The original GPS is damaged.
Original GPS would not accept any commands or configuration. RX line on gps faulty inside the module.
New Mediatek works perfectly.
Thanks for all that chipped in!
John, that's great. I won't throw that "bad" MTEK GPS away yet. Chances are it's just the rx line on the connector is bad. It's not switching into binary mode because the APM does it by sending the command via rx. This is why when connected through FTDI, the MTEK display NMEA properly.
Could be as simple as replacing the cable on the MTEK to get it working again.
Thanks mate... good thought....
Multiple cables tried, even attaching to the pads that are on the underside too..
Belled the connector and pads all the way through the DIY drones adapter board all the way to the little surface mount tag that mounts the GPS module to the board.
Found that I can only read via the FTDI cable, I can't configure the GPS via FTDI either.... only listen.
When I use a teminal program in conjuction with an ftdi adapter (using Mediatek commands), it won't aknowledge reciept of those commands... and the tx light (data into GPS) when attempting to send a command is extremely dim compared to the rx light (data from GPS) which is pulsing nicely in unison with the NMEA data coming in.
I really should protect my GPS a little better.. there was a lot of dew around on the grass after my last flight. Maybe a couple of drops got inside and wreaked havoc. I have now made a foam cover to keep the drips away.
On the positive side. At least this may help someone troubleshoot in the future.
Thanks again for the input.