Eagle Tree + EB-85

[drPhibes]

Does anyone here know exactly what I need to do to connect my EB-85 GPS receiver to my Eagle Tree eLogger v3? (without buying the 45$++ adapter board).

If the eLogger transmits/receives standard 8N1 UART (4800 or 38400bps), all thats basically needed is a simple logic level converter from the eLogger's 5V TTL I/O to the EB-85's 2.8V. Can someone confirm that this is the case, or does eagle tree use some other protocol between the eLogger and their GPS units/adapters?

Thanks in advance,
J

[Fluffy Monster]

EagleTree use I2C for talking to some of their device such as the LCD. Maybe that is why the board is $45?

[lajon63]

I can confirm it works, I have tested it with my EB-85 GPS module a while back (I have not done any actual GPS logging while flying yet). The eLogger expects the GPS is configured for 4800 baud and send the command to switch it to 38400. I had some trouble getting it to work initially, this might have been becuase my module was configured for 38400 already.
/Lars

[13brv3]

I've done this, and it worked fine. The ET uses 38400 for the GPS, and that's what all my EB-85s use as a default. I don't think the ET sends any info to the GPS, but I hooked up the wire without any level shifting (5V from ET to the GPS). The data sent from the GPS has to be raised to 5V as you mentioned.

All that being said, I bought the adapter when it came out, because it's a nice neat package, and includes a battery which typically speeds up acquisitions.

Rusty

[lajon63]

The ET does some setup, I logged it but can't find the file now, from memory it was the speed setting (but then only if needed I guess), then PMTK_API_SET_NMEA_OUTPUT (this is command 314 to set which NMEA sentences the GPS will send and how often). Last was the command to enure 5Hz update (PMTK_API_SET_FIX_CTL).
/Lars

[13brv3]

The ET does some setup, I logged it but can't find the file now, from memory it was the speed setting (but then only if needed I guess), then PMTK_API_SET_NMEA_OUTPUT (this is command 314 to set which NMEA sentences the GPS will send and how often). Last was the command to enure 5Hz update (PMTK_API_SET_FIX_CTL).
/Lars

Hi Lars,

No doubt you're correct about this. Thanks for the info.

Rusty

[drPhibes]

Thanks for the info. I'll make a simple schematic w/level shifter and backup battery, and post it here when I'm done.

I'll be using a 2.8V voltage ragulator and some small signal transistors for the level shifting. The EB-85 accepts 3-5V as VCC, but I might add a diode (1N400x-series) in line with the receiver for an approx. 0,7V drop in VCC (this probably isn't necessary,but I might as well play it safe with my 100$+ GPS).

With everything built on a prototype board, it shouldn't cost more than a few $ from the local electronics supply store (Elfa).

Btw: Which pins on the eLogger is tx/rx? 1 (red) = VCC, 2 (white) = GND, 3 (yellow) = ?, 4 (orange) = ?

-J-

[lajon63]

I don't have the cable I made here but as I recall the pinout was the same as for the GPS (which has TX on pin 3 and RX on pin 4). Note that you need to connect EagleTree TX to GPS RX and EagleTree RX to GPS TX.
So Elfa is your local store, same here, maybe we live in the same country? :D
/Lars