14 replies to this topic

[Count]

Hi,

I have a Ublox 6 based GPS module and it is working fine, as long as I connect it to my PC through a USB2TTL adaptor. I tried it with the u-center software, GPS Utility and in GCS as GPS Mouse and Flight GPS connected through serial.
But as soon as I connect it to the CC Board Flexiport, it does not get a fix (constant green LED) and it is shown red in the GCS System Health gadget. I activated the GPS module under "HWSettings>optional Modules" in the UAVObjects Browser. Both CC and the GPS are set to 57600baud.
Did I miss a setting or do I have to select only certain NMEA messages? Does it only show up green in System Health, if it gets a fix?

Sebastian

[Rusty]

Hi Sebastian,

I've struggled with this as well.  I've tried several different GPS units, and getting a lock is a real challenge.  I spent quite a lot of time testing this, but eventually had to move on to something else without coming to any real conclusions.

There certainly seems to be something about connecting to the CC that makes a lock difficult.  I ran two identical GPS units on the table next to each other, one connected to the computer, and the other to the CC.  The computer GPS locked, and the CC didn't.  I switched the connections around several times to verify that it wasn't the actual GPS, but rather the connection that was at issue.   At some point, I'll have to do more testing, and maybe put a scope on the wires from the CC to see if I can see any reason for it.

I can get a lock on an old EB-85A, but it appears to be weak.  On the health gadget, red is actually good.  It seems to indicate that the GPS is communicating, but doesn't have a lock.  It will turn yellow when you get a lock, and eventually turn green at 7 sats.  What you don't want is white with a red X through it, since that means it's enabled but not communicating.  

As for NMEA messages, I have no idea what is needed.  I've tried various settings, but that's not the lock issue of course.  It would be nice to know what messages are needed, so the others could be turned off.  

I do know that David has spent plenty of time with GPS units, and apparently doesn't have issues with locking.  I'm not sure what the difference is though.  

Cheers,
Rusty

[Count]

Thanks for your reply Rusty. I really thought I missed something obvious, but it seems it is not as easy as "you can hook up any NMEA GPS". Something I read in the meantime states, that it could be a powersupply/voltage issue. Some GPS units seem to be really sensitive (never getting a fix) to little voltage variations or too little voltage. I think, I try to split the connection and only hook up RX/TX to the CC, powering the GPS from the TTL adaptor. I hope I do not break anything. It should not take too long, since everything is right in front of me.

Sebastian

[Count]

I now tested it both ways, powered through usb, RX/TX connected to the CC, getting no fix and powered through the  CC and RX/TX hooked up to the TTL adaptor, getting a fix in no time. It also can not be some kind of interference, because the GPS module is mounted as if flightready, near to all other antennas.

[peabody124]

My guess would be EMI issues then from CC.  On Revo we added more filtering to the serial port explicitly for this.  I remember having similar issues with the original main board.  It would work fine standalone (powered through serial port) but when I added the PipX that would propagate noise via the power supply line that would interfere with GPS.

[Count]

I have an Apc220 connected to the main port, maybe i should remove it and see how it goes.

[Count]

Success! I changed a few things on my T-Copter and just went outside for a short testflight. Suddenly, I noticed the LED on the GPS module was blinking. Unfortunatly I left my netbook inside, so I have to do it again, to see what GCS is showing. But the GPS never got a fix before, while connected to the CC. And the APC220 is connected, too. I do not know why it is working now, I changed the mixer settings, rotated the CC 180° yaw and ( I know it is bad) have connected all BECs to the CC-Board, perhaps the GPS is getting more power this way (just a wild guess). Will test it again tomorrow and this time with my netbook.

Sebastian

[miniplanes]

HI Sebastian, could you tell me how do you have you APC220 modules conected to the PC and Copter ?
Did you followed the Wiki instructions using the Bluetooth module or have you conected these modules directly to the comunication ports (PC and CC board) ?

thanks

[jakestew]

I had trouble with a GPS connected through a cheap Chinese TTL adapter.  It would only lock outdoors, and wouldn't get very good reception even then.

So I can verify that they're pretty sensitive to interference.  Fastrax makes a model with an extra SAW filter, which they claim is good for telemetry applications where the GPS is near a transmitter.

[Count]

miniplanes, on 28 February 2012 - 01:50 AM, said:

HI Sebastian, could you tell me how do you have you APC220 modules conected to the PC and Copter ?
Did you followed the Wiki instructions using the Bluetooth module or have you conected these modules directly to the comunication ports (PC and CC board) ?

thanks

First I connected both APC220 modules to my PC using the provided USB2TTL adaptor and configured them according to the wiki. Then I left one connected to my PC and connected the other one to the CC boards MainPort. I made the connection cable from the JST-SH4 cable that comes with the CC, cut off one connector and crimped servo terminals to that end. The software to configure them was kind of hard to find, it seems RF-Magic is discontinued. I post a zip with the software I found.
The connection itself is like any connection through a serial port. GCS does not care or does not know, if it is a cable, bluetooth, or a serial RF link.

Right now, my copter is on my balkony and I am 20m and several walls away from it, watching the GPS data, so the APC220 works just fine.

One thing you should know, you can configure the APC220 to different frequencies, be careful to pick one that is legal in your country. (433MHz is alright in Germany and maybe for Portugal)

Good luck,

Sebastian

Attached Files

•  apc220.zip   740.74K   3 downloads

[Count]

jakestew, on 28 February 2012 - 06:17 AM, said:

I had trouble with a GPS connected through a cheap Chinese TTL adapter.  It would only lock outdoors, and wouldn't get very good reception even then.

So I can verify that they're pretty sensitive to interference.  Fastrax makes a model with an extra SAW filter, which they claim is good for telemetry applications where the GPS is near a transmitter.

All I did was disabling the u-blox NMEA extensions and now it works just fine. I have a fix with 6 SVs near to a wall and with a balkony above it. Will test it on an open field in the future.

[jakestew]

I scoped the 3.3v output from the cheap USB-TTL and it was better than I thought, but still fairly dirty.  It was also injecting noise into the computer audio (crappy computer audio system also).  So I soldered a cap across the USB 5V-GND and it really seemed to clean up the power supply.

I think it's still putting some noise out in the 1G range, where I can't see it with my scope.  Hopefully I can eventually figure out a proper filter for the setup.

Right now if I power it from the TTL adapter it gets only a few signals inside.  If I power it from my dev board it's a little better.  And it's pretty decent if I use a battery.  This is all without a transmitter involved, so I've probably got some work to do.


-Jake

[miniplanes]

Count, on 28 February 2012 - 01:58 PM, said:

First I connected both APC220 modules to my PC using the provided USB2TTL adaptor and configured them according to the wiki. Then I left one connected to my PC and connected the other one to the CC boards MainPort. I made the connection cable from the JST-SH4 cable that comes with the CC, cut off one connector and crimped servo terminals to that end. The software to configure them was kind of hard to find, it seems RF-Magic is discontinued. I post a zip with the software I found.
The connection itself is like any connection through a serial port. GCS does not care or does not know, if it is a cable, bluetooth, or a serial RF link.

Right now, my copter is on my balkony and I am 20m and several walls away from it, watching the GPS data, so the APC220 works just fine.

One thing you should know, you can configure the APC220 to different frequencies, be careful to pick one that is legal in your country. (433MHz is alright in Germany and maybe for Portugal)

Good luck,

Sebastian

Thanks for the help, one more thing... are you using these rf modules @ (1, N, 8, 9600) or did you managed to get more speed, these are suposed to work at that maximum, but perhaps a little more can be achieved ?

edited: the Rfmagic doesn´t detect my APC modules, i´m using win7 - 64bits, no comm port is detected with the USB and module connected !!!



thanks

Edited by miniplanes, 28 February 2012 - 06:08 PM.

[Count]

I set the wireless link to 19200baud and so far I had no problems.
If you see no new comm port, change your USB connection. My USB2TTL adaptor is not detected or marked with exclamation mark in Device Manager, If connected to an USB-Hub or front USB port. Connection with an USB extension to a rear USB port works just fine.
You have to start RF-Magic as administrator, otherwise you get an error message.

[miniplanes]

Hi guys, problem fixed... i could install new USB drivers (win 7) for the APC 220, now i can detect these modules, adjusted config as stated at Wiki, and now i got telemetry as it should be !!!

thanks for the tips

Edited by miniplanes, 29 February 2012 - 01:12 PM.