Yes, I requested an SDK token back on 15-May. Except for the auto-generated immediate response, it’s been crickets. Maybe they ran out of tokens and are waiting for new ones from China (joking)?
–Richard
The “paired but bereft” “mode” is a great trick. I’ve been wanting to experiment with relaying through a GTM mounted atop my Mavic Pro. I know “atop” puts the drone battery and some other bits between the GTM and the world, so really wanted a way to see if the top-mounted GTM is reachable. I’m assuming that some XY-offset will allow me, as pilot, to talk to it, but was really loathe to send a GTM and a phone up for experiments. With your approach, I can see under what positional relationships I can reach the drone-mounted GTM. We camp well out away from cell service (think: southern Utah, eastern Oregon) where LOS is hard to come by. Am hoping a drone-mounted relay would allow us to touch base at scheduled times with travelling companions we would otherwise not reach. Scheduling will matter…usable time aloft is going to be ~15 minutes. So reduced GTM battery life won’t be a constraint.
I have the mount printed…it’s not perfect, but will work, and is pretty light. Went out to do some experiments today, but about the time I got somewhere sufficiently unoccupied to fly, the wind really picked up. I’ve flown in worse, but not with something sticking up 4" above the drone.
With luck, it will catch some air tomorrow.
–Richard
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From what I’ve seen you should be able to easily reach the mavic mounted GTM from 400’ or less no problem. I bet it would work great in a pretty large radius underneath your hover point as well. All that said is provided you don’t have any interference from the quadcopter. The one time I tried something similar with an M200 the GTM seemed to interfere with the M200’s gps location accuracy and it wanted to move around a lot by itself trying to stay in what it thought was one place. It was enough of an issue that I haven’t tried it since. I suspect that with some more testing we could have found something that works. I hope the mavic doesn’t have the same issues.
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Yeah, it’s why I want the first flight to be well away from anything and anybody, on a calm day. So if things go south, I can just push the vertical stick forward and set it down. Hopefully.
–Richard
Did the experimental flight at a park just under a mile from my house…but with a substantial ridge in between. Left a phone with a GTM in a ground floor window at home. Could ping it until I crossed the ridge, and then nothing.
Woke the “air drone” up, let it pair with my iPad Mini, and then killed the GTM app there. Gently took off…no sign of GPS or compass interference. Was probably 30 feet horizontal away from launch point. Ran the drone up to 200’, it pinged fine, no communication back to home. Ran it up to 400’, the FAA ceiling, no problem pinging the GTM on the drone, no luck pinging home. Landed the drone, changed the max ceiling to 750 (temporarily), relaunched. Got a warning when it passed 400’. Stopped at 500’, drone GTM still pinged, still nothing to home. Stopped again at 610’, and could both ping the drone GTM and ping home relaying through it. Brought the bird back down, changed max ceiling back. The drone handled like always. Given the angle you get with 30’ lateral against 610’ vertical, the GTM clearly had no issue getting signal straight down through the drone battery and body.
So it worked! I was a little surprised how much height it took, but fed the launch point + 610’ into heywhatsthat.com, and my house is just barely in the coverage shadow for LOS. This is mostly because our house is very close to the bottom of the ridge…there’s a 12% grade sidewalk to get up to the top. It’s the main reason I abandoned the idea of placing a stationary node on our property.
So this silly little bracket will go with us, along with the GTMs and the drone, when we head off into the wild.
–Richard
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That’s good news! Is the mavic mount available on thingiverse or elsewhere?
The original Mavic Pro battery mount is here: https://www.thingiverse.com/thing:3203638/files
I used Blender to shave the top off flat. I rolled my own two-piece GTM holder…the latch attaches to the base via a M2 screw. Glued the base onto the shaved Mavic mount…there’s really no way to print that as one piece without a ton of supports. The latch could be more snug, but I can pick the drone up by the GTM. I went ahead and threw a rubber band around the latch and GTM for flight.
This forum seems not to be willing to allow upload of my STL files. If you really want them, I can email them to you.
–Richard
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Impressive! Thingiverse will be just fine. Thanks for sharing
So I now have an SDK token, have a Pi Zero W set up, experiments will proceed.
But wanted to give you some hope. It’s not zero-lift, but it’s doable. If you don’t care about verifying status (the “bonus points” section at the end), it’s really not much.
I discharged a GTM completely…just left it on until it quit blinking. Connected it to my Pi Zero W via OTG cable, powered the Pi up. GTM started charging, as expected, and was fully charged after about 2.5 hours.
There’s a section in the SDK Python doc that’s interesting:
This suggests that even after total power loss, upon power restore, if only there was something smart enough to exercise these SDK commands connected via USB, the GTM could be put back into relay service mode.
In your situation, my attack on this would be to use a Pi Zero W and a Witty Pi 3. The power from your supply feeds the Witty Pi 3, which plugs in as a “hat” atop the Zero. It allows scheduling power-up/power-down/wake-up of the Zero…it has an on board CR2032 for RTC, which looks like would be good for about 6 years between replacements. I’d set it up on a daily schedule: wake for 3 hours or so every morning to fully charge the GTM, and allow the Pi to do whatever SDK housekeeping is required. At a minimum, put the GTM into relay mode before retiring. I’ll need to verify that once put into relay mode, the GTM stays there when the power drops, but see no reason why that wouldn’t be the case.
(bonus points)
The stretch project would be to have the Pi, upon wakeup, put the GTM into “normal” mode, configured with an SDK token, known GID per relay, and respond to messages. Of course, it would keep right on relaying during that time. And then before going nighty-bye, switch the GTM to relay mode.
For this last to be useful, you’d need a companion SDK app for your phone (or whatever), using the same token, that could ping/query the relay while it had a “personality”. Aside from needing to construct the app (which could be pretty bare bones), this shouldn’t be much overhead from what you’re doing now. The GTM would run at lower power. The Pi would only be up for 3 hours per day, and by turning off wifi, BT, etc, can get down below 100mA while it’s awake. Of course, it’d be charging the GTM then, so the 100mA5V3H gives you an added daily load of 1500mAH. I suspect the Pi could shut itself down sooner, and let the Witty Pi continue to supply power to charge the GTM…in which case, that 3 hour window could be as short as you are comfortable with, probably sub 1 hour. The WP would still wake it up back up on schedule. Either is a bite out of your V50 capacity, but when the sun comes back out, it all wakes back up.
The PZW and WP3 each run somewhere around $50. This seems like a better approach than punching the power button with a plunger. I’ll try to verify that the GTM stays in relay mode if put there via SDK when the controlling device shuts off. I’m positive the WP3 can wake the PZW…it’s done over GPIO.
–Richard
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Never mind. It appears the SDK is full of excrement. The GTM may indeed be in some “special mode” when it’s off and power is applied, but it appears to be unreachable…doesn’t even show up as a device via “lsusb” until you power it on. And even then, it appears you have to set a GID (which relay mode would ignore) and jump through more hoops to get “connected” before you can call set_operation_mode(). So it looks like once you jump through enough hoops, you could change to relay mode via Python, or (swell, right?) turn the device off. I’ll keep poking. The SDK doc really seems to differ from what I am seeing here.
Don’t give up on the solenoid.
–Richard
I’ve given up on the solenoid in favor of opening the GTM case and wiring direct to the GTM switch contacts. It works well enough for my needs but anything to conserve power means the GTM would be on more. It’s cool to see you experimenting with all this but to be honest All that you are doing is way over my head! Keep going with it though I’m sure lots others will benefit.
In for updates on this one!
As a firefighter (very small, rural, all-volunteer dept.) in the southern Idaho mountains, I’m interested in setting up a mesh network here in my community, so I hope this thread keeps going. I just ordered a pair of GTM that should be here in a couple days, so we’ll see how it goes when I get to testing.
Now… if only that ATAK-CIV plugin could be made available for GTMs again!
I’ve got 5 mountain top relays all happily ready to relay messages. All are now solar powered with the V50 Or sla battery and modified to restart. Each of the relays I placed last year had some outages throughout the winter snow but all restarted themselves as hoped. Now that summer is here I don’t expect any outages until the fall/winter weather sets in. I just messaged each one today and all messages were confirmed. These relays give us communications in several comm free areas already but it’s also really easy to increase coverage just by adding a temporary relay. I hope for some more GTM win stories as the season progresses. With our traditional radios on the decline and issues with cell service the chances are increasing for the GTM network to save the day. I’ll be sure to share as they arise.
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All the relays stayed in service all summer but unfortunately I don’t have any communications win stories. The relays are now off and on as the sun and snow come and go.
I guess one win would be that it’s been close to a year since I’ve had to visit most of my relays and one hasn’t been touched for 2 years now as of last month!
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