APM 2.6 3DR Ublox LEA-6H rx and tx pins

[JP B]

Hi all,

Currently writing some custom firmware for a rover, using the APM 2.6 as the micro-controller platform.

I have attached a 3DR UBlox LEA-6H gps and I am trying to use the Tinygps/Tinygps++ libraries for GPS processing.

Does anyone know what RX/TX pin numbers may be assigned to the GPS port on the APM 2.6 (As I will have to set these up using SoftwareSerial).

Many thanks in advance, much appreciated.

[JP B]

Just to further elaborate, I can get data from the GPS using the sketch in this article:

https://sites.google.com/site/wayneholder/self-driving-car---part/evaluating-the-3dr-ublox-lea-6-gps

Which, as far as I understand, is processing the NBX protocol sentences from the GPS.  I also understand however that the LEA-6H is multi-protocol, and is set as such as standard (?), so at a loss as to why I cant see NMEA sentences which I can process with tinygps example sketches.

Any advice/pointers most appreciated.

[Ben Nizette]

On 30/10/2013, at 7:24 AM, JP B wrote:
>
> I also understand however that the LEA-6H is multi-protocol, and is set as such as standard (?), so at a loss as to why I cant see NMEA sentences which I can process with tinygps example sketches.

Regarding this point, are you using a GPS module from 3DR?

The LEA-6H modules sold specifically to interface with APM often have a permanent configuration programmed at the factory to suit APM usage. Amongst other things, all NMEA messages are disabled. If you don't want this, you can issue the UBX CFG-CFG message with a full clear mask to reset to factory defaults, see uBlox Receiver Protocol Spec Section 5.

HTH
--Ben.

[JP B]

Hi Ben,

Yes that helps, thanks very much.  I am indeed using the 3DR LEA-6H GPS module from the 3DR APM 2.6, however I am using my own custom APM 2.6 firmware sketches (not Ardurover or Ardupilot etc).

I think longer term it will be useful for me to cobble together a JST to FTDI cable to allow me to configure the GPS via U-Centre, I have seen some wiring diagrams such as this one:

http://paparazzi.enac.fr/wiki/Sensors/GPS#Wiring_Diagram

although I'm not sure what voltage the GPS runs on hence wondering if a line level convertor from 5v 3.3v is required.

I'm also currently evaluating whether just to proceed with working with the current default UBX protocol or change configuration to get NMEA messages.

Thanks.

[Ben Nizette]

On 30/10/2013, at 6:53 PM, JP B wrote:
> although I'm not sure what voltage the GPS runs on hence wondering if a line level convertor from 5v 3.3v is required.

The GPS is 3.3V but you shouldn't need a level translator per-se, just use a USB to serial with a 3.3V I/O like the venerable https://www.sparkfun.com/products/9717

The other week I had to make up exactly this kind of cable and hacked something together out of an old xbee/usb breakout board I had lying around

>
> I'm also currently evaluating whether just to proceed with working with the current default UBX protocol or change configuration to get NMEA messages.

Which protocol to use is up to you, but don't let changing the config make the decision for you. To reset to factory defaults right now, all you have to do is to hack your Arduino code to send the following bytes once and you're golden:

0xb5 0x62 0x0c 0x00 0x00 0x06 0x01F <checksum>

--Ben.

>
> Thanks.
>
> On Tuesday, October 29, 2013 11:38:26 PM UTC+1, Ben Nizette wrote:
>
> On 30/10/2013, at 7:24 AM, JP B wrote:
> >
> > I also understand however that the LEA-6H is multi-protocol, and is set as such as standard (?), so at a loss as to why I cant see NMEA sentences which I can process with tinygps example sketches.
>
> Regarding this point, are you using a GPS module from 3DR?
>
> The LEA-6H modules sold specifically to interface with APM often have a permanent configuration programmed at the factory to suit APM usage. Amongst other things, all NMEA messages are disabled. If you don't want this, you can issue the UBX CFG-CFG message with a full clear mask to reset to factory defaults, see uBlox Receiver Protocol Spec Section 5.
>
> HTH
> --Ben.
>

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