UPDATE: See the manual.
Hey guys, this is mainly a question for our friends at 3DR, but anyone who has looked at the traces on the APM2 daughterboard, and knows the GPS module, could offer ideas.
I wonder what you'd think about (as a hack, as a revision to the APM2 daughterboard, etc) installing some jumpers or switches to "disconnect" the onboard GPS, as needed. We might also add a battery socket to maintain the almanac, for those who want to accept the extra weight of the small battery, but that is another topic.
I have a small but growing fleet of APMs, some APM1 and some APM2s. However, I never have enough, so I find myself swapping them around as needed. I leave the magnetometers, air speed sensors in place and connect them as needed. Some airframes are better served with an external GPS, but I would prefer to have all my APM2s be, physically, the same. That is, I'm willing to buy all my APM2 with the extra cost of the onboard GPS whether or not I need it, in order to ease my "fleet management" if you will. If the daughterboard were not soldered in place, I might instead get extras, but this approach might work best.
However, I would also like to buy or use uBox and other external GPS units, as needed. I think this represents opportunities for the 3DR and affiliate stores. Many users will purchase the APM2 w/GPS, and some will later decide they want to use an external. Some will buy a separate unit w/o the GPS, but most will not. Most of the population simply live with the existing GPS. However, if there were a switch or jumper(s) to kill the onboard GPS, then casually swapping to an external GPS (and, casually purchasing additional GPS units) is easier. It also allows for subsequent upgrades (opportunities for sales) to future GPS units.
As a hack, are there recommendations on which trace(s) are best to cut and/or install a jumper for an existing APM2? I imagine there are a couple of ways to do this, not all are ideal. Is there any merit to a revision of the APM2 where there is a jumper or switch for the GPS?
The next rev of APM 2 will have that.
Does that mean that there is no way to make the GPS antenna separable from the current version? I was considering buying another mediatek from the diyd store and cabling it back to the tail so it'd stay away from my Frsky 2 way receiver.
Is this not possible on the current board?
The current board comes in two versions: with built-in GPS and with external GPS. If you buy the first kind, there's no easy way to disable to built-in GPS. Maybe in a future version we may enable that, but right now if you want to try different GPS modules choose the version with the external GPS.
Hi Chris. I too am working through GPS lock issues. (only since 2.6 FW).
Will there be the ability to just purchase the daughterboard separately with only the Flash mem onboard. Then we could simply swap it out, and use an external GPS module. No mess, no fuss, no hacking traces, bridging with Resistors etc.
thanks very much
You can easily remove the U3 on the shield (this cuts the power to the GPS module) or you can do a mod like I show in the attached PDF file
Mehdi: Thanks for that, but I had a bit of trouble following the schematic. Any chance you can post a tutorial, which photos, so we can link to in in the manual?
What I actually did was that I de-solder the GPS part and got the GPS board with no GPS mounted from 3DR and soldered the GPS back on that board I will see if I can post some pictures later or you can simply remove the resistor looking part (it is actually a ferrite) called U3 from the board and simply use an external GPS. I hope this was usefull
When is the release of the new revision APM 2 planned?
No doubt as Chris says, in a later hardware release, all will be good. As for those of us now with the current hardware we own, posed with the need (for whatever reason) to implement external GPS, where do we turn? Below refers to another of your posts on the same subject
If I don't get an answer there, I will eventually start cutting traces on one of my boards to figure it out myself, and I will post something there. Either way, we'll have an answer there eventually.
Let me know when you go for the chop Mike, I'll go in sympathy with you. I have just been through 15 odd pages of the hardware forum and found 10 threads started on the same topic, for nil posted results. One member has apparently done it successfully but could only manage to post a thumbnail size picture of his attempt. I have familiarized myself with the Tx pin on the gps unit and feel confident enough to give it a snip.
In my case I will just need to make sure I have earth continuity between the other gps unit I have installed in the aircraft (for antenna tracking) and then piggyback the Tx from that unit onto the daughter board of APM2. Should that not work, I have a U-blox to try on the external gps header.
5 minute job............ ... :)
Any comments on the chance of success with this mod Chris? I figure if it all goes pear-shaped I'll have an excuse to buy the external gps version of APM2 right? :)
I have been considering cutting the trace that is closest to the "reset" button, which should be power. This way, the onboard GPS does not even power up, saving a tiny bit of juice. I suspect this will kill the 3D fix LED onboard, so you can easily see that this APM2 has a non-functional onboard GPS. Then, just plugging in an external GPS should work without additional changes.
However, there are a few things I'm not certain about yet -
* Will the onboard GPS unit "leach" power from the RX/TX lines, or other connections, and power up partially, or create other problems?
* There is nearly enough space to put in a jumper, however, I have not sorted out how to make it mechanically sound. The risk of a hacked in switch or jumper disconnecting during flight is too high, in any way I've considered so far...so once cut, the onboard GPS can only be used again with a very careful solder job.
Are there any thoughts on a better way to do this? I think this is easier and better than cutting the TX line, which does not appear to be accessible, largely because cutting the power reduces the draw on the battery (a tiny amount) kills the GPS Fix LED onboard (as a visual indicator) and is accessible to be cut without removing the soldered-in daughterboard.
I want to do this too. Could we solder a resistor between the enable pin (2) and ground do you think? This is probably the least intrusive first test.
My main concern would be the TX and RX lines still being connected to the disabled module...