$25 GPS Solution

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I recently seem to have had a total lapse of cognitive ability and have been staring at my USB to micro USB adapter here:

https://www.aliexpress.com/store/pr...-mobile-phone-to-USB/1988232_32669867029.html

for days with the idea that it was an OTG adapter, which is not, and they are not the same. Micro OTG requires a jumper between pin 4 and pin 5.

I just ordered a hand full of micro OTG adapter cables but in the meantime I will make one for testing purposes from some old cables I have. After I get it built I will re-attempt using a few of the Android applications that I was unsuccessful with previously and hopefully report back with a Bluetooth-less solution.

Edit: Or maybe what I have is an OTG adapter and not just a USB to micro USB adapter. Still researching.

You have to remember, if you are going to plug in a dongle/receiver that is going to require a power source, it's going to suck it from your device's battery and your run time is going to be very limited. Trust me on that one. Running the screen as bright as it can, the onboard GPS for local position full time and having to power the outboard dongle from your device's battery is going to run it down extremely fast without a means of external power.

Now most OTG devices cannot use a simple Y cable to apply external power AND have a USB dongle connected at once period. If you look at that ElementalX
address I posted above, some devices can be modified to do so but there are just a few of them. If you don't own one, don't know how to "root" your device, you will be out of luck and your tracking time will be constrained.

I do not think that receive Dongle for those 3DR radios are passive. That is they take power from the device to run and I don't think it pipes the NMEA strings over B/T directly. It's meant to decode from USB and go from there. Yeah you might be able to use your device to pipe the incoming strings over B/T to
"another" device but why do that? Use two devices? That sounds awkward.

Best strategy is to decode the NMEA strings right off the receiver in a local mapping app period. Kurt
 
I didn't realize that the linked radio was USB only. I thought it was like these...

https://ardupilot.org/copter/docs/common-sik-telemetry-radio.html

Those have a UART output that can connect directly to a BT module or any other UART device. If you only have USB, you would need an OTG cable. Or I guess you could use a USB Host/OTG microcontroller and translate it, but that's a lot of work when you could just plug it in.
 
If you buy a second 'air' module you can program it to suit and then use the tx and rx pins directly into a bluetooth module.
I disassembled a USB charge pack to install an air module, hc06 bluetooth module and a battery into.
If you get a 2 or 3 cell USB battery bank you can keep 1 or 2 of the cells inside to supply you with a power supply for the unit with a built in charger.
Inside the smaller single 18650 cell units you can normally fit a 600mAh battery with room for a bluetooth adapter and an air module.
file.php

I wire a plug outside the case for the battery which allows me to use it to charge my tracker battery from any USB power supply.
 
You have to remember, if you are going to plug in a dongle/receiver that is going to require a power source, it's going to suck it from your device's battery and your run time is going to be very limited.

You can buy a cheap 5V powered hub and power it with a cheap 12V to 5V USB power supply... Then plug the radio into the hub.
 
I've gotten lost at this point. Its clear that some of you know this a lot better than me, I am still learning though, and I'm just going to sit and watch this thread and hope that someone can figure out a way to make this work. I'd love to experiment but I just don't have the money too.
 
If you buy a second 'air' module you can program it to suit and then use the tx and rx pins directly into a bluetooth module.
I disassembled a USB charge pack to install an air module, hc06 bluetooth module and a battery into.
If you get a 2 or 3 cell USB battery bank you can keep 1 or 2 of the cells inside to supply you with a power supply for the unit with a built in charger.
Inside the smaller single 18650 cell units you can normally fit a 600mAh battery with room for a bluetooth adapter and an air module.
file.php

I wire a plug outside the case for the battery which allows me to use it to charge my tracker battery from any USB power supply.

So, the "transmitter" is actually a transceiver and you are using a second "transmitter" as a receiver? I don't understand the use of the B/T module if that is the "air" tracker? I can see the B/T module as a convenience to program the tracker but I think
it would be highly desirous to have a receiver that can send the strings over B/T to a device for interpretation or mapping.

What I'm looking for is something like the EggFinder/EggFinder LCD arrangement. Put the HC-06 B/t board in the LCD receiver and it sends the strings to the Android/Tablet device wirelessly for processing or mapping.

Wires, cables, and dongles can get jostled if triapsing out to a recovery site and can really mess up one's day if the system halts. Can the 3DR receiver be modified to use an HC-06 B/T board? If so, I have a USB battery source that can power the Dongle directly. Kurt
 
So, the "transmitter" is actually a transceiver and you are using a second "transmitter" as a receiver?


Correct. Both 3DR radios are transceivers.

PC is plug and play for the USB Ground 3DR with all the GPS programs I've used (windows 7). Maybe if someone has a Windows tablet or some other portable windows device they could plug in the ground 3DR and run U-blox (u-center) or some other PC program to verify functionality. If it works, well good for the windows users. But I want a portable android solution using an air side and ground side 3dr radio (not two air side radios).

I am still working on OTG and Bluetooth solutions for Android. My device (S4 Galaxy) supports host mode and OTG but I can't figure out how to make it work with any of the programs I've tried with the OTG cable I just pieced together. All I did was solder bridge pin 4 and 5. The ground 3dr gets power and pairs with the air radio, but that's it. So far I have used droidplanner, andropilot, gnss comander and a couple others with OTG and can't get anything to work. I'm guessing the programs aren't able to find a vehicle or give coordinates because I am sending only NMEA data back from the GPS antenna/air side 3dr instead of plugging the air side 3dr into a flight controller as they were designed to be and getting some other data from the flight computer that the programs need to run.

As far as bluetooth, I understand that USB signal works differently than serial data in that there are no Tx and Rx signal wires in USB like there is for serial data. Hence FTDI chips. This must be why Vance down under used an airside radio on the ground. What I am trying to figure out is the difference between the air side and ground side radios. I assume the difference is the serial to USB conversion, in that the air side radio does not convert but the ground side does so to be plug and play for PC.

1) Will I have to throw an FTDI board between the ground radio and HC-06 module?

2) Can the HC-06 be connected directly to the ground radio?

3) Why can't this be easier?

Vance, chime in if I am on point or need clarification on your setup.
 
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1) Will I have to throw an FTDI board between the ground radio and HC-06 module?

I don't think that will work. A host controller has to communicate with your ground radio. FTDI chip converts serial to USB, not the other way around.
 
I don't think that will work. A host controller has to communicate with your ground radio. FTDI chip converts serial to USB, not the other way around.

You're right and I have just been able to do some more research. The ground radio has a conversion chip. I just need to figure out how to tap into the serial data for the HC-06. I need to look up the specs on the radio I have. There are genuine 3DR radios and there are clones. My clones do not use hope radio modules, they use some other radios with SiK firmware. I need to get schematics n stuff.

I just searched youtube really quick and found this, skip to 2:57:

[video=youtube;rRR_MvRC02U]https://www.youtube.com/watch?v=rRR_MvRC02U[/video]
 
My ground radio:

20170727_214957.jpg20170727_215412.jpg

It appears as though any soldering to serial leads may be impossible. This thing is way small!

I'm researching the radio specs now.
 
You're right and I have just been able to do some more research. The ground radio has a conversion chip. I just need to figure out how to tap into the serial data for the HC-06. I need to look up the specs on the radio I have. There are genuine 3DR radios and there are clones. My clones do not use hope radio modules, they use some other radios with SiK firmware. I need to get schematics n stuff.

I just searched youtube really quick and found this, skip to 2:57:

[video=youtube;rRR_MvRC02U]https://www.youtube.com/watch?v=rRR_MvRC02U[/video]
That video.... That is exactly what I was thinking about. However, what does that third board do and is it necessary for our purposes? With this video I think it could easily be done using Bluetooth and now the trick is to just find a nice software that reliably works with this.
 
If you buy a second 'air' module you can program it to suit and then use the tx and rx pins directly into a bluetooth module.
I disassembled a USB charge pack to install an air module, hc06 bluetooth module and a battery into.
If you get a 2 or 3 cell USB battery bank you can keep 1 or 2 of the cells inside to supply you with a power supply for the unit with a built in charger.
Inside the smaller single 18650 cell units you can normally fit a 600mAh battery with room for a bluetooth adapter and an air module.
file.php

I wire a plug outside the case for the battery which allows me to use it to charge my tracker battery from any USB power supply.

Vance, to what device are you sending the data (over bluetooth) and what program/s are you using?
 
That video.... That is exactly what I was thinking about. However, what does that third board do and is it necessary for our purposes? With this video I think it could easily be done using Bluetooth and now the trick is to just find a nice software that reliably works with this.

I think the third board is just an adjustable power supply or something because he's using a big 3S and 2S batteries. It's not necessary as long as you only use a 1S, 3.7v lipo power source with this stuff.

Here is my exact problem already encountered:

https://diydrones.com/forum/topics/mini-3dr-radios-v1-6-bluetooth-bridge-problem

Since the 3dr radios I linked in the first post are clones and do not use hope radio modules the circuitry is extremely small! Check out the attachments on that link. Not sure how I'm going to solder to the radio board...
 
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CORZERO,

I think you have found everyone a nice cheap solution for GPS. I'm going to attempt to see if i can order this and get it here before i start school (AP classes take up lots of time) and get it done and in the nosecone of my level two. I might even see if i can pop it in someone else's rocket to test it out.

These are what I will use to build this::
GPS
Guide
Battery

Now should I use HC-05 or 06 because the guide uses 05 but 06 seems to be the same just a newer version?
HC-05
HC-06
 
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CORZERO,

I think you have found everyone a nice cheap solution for GPS. I'm going to attempt to see if i can order this and get it here before i start school (AP classes take up lots of time) and get it done and in the nosecone of my level two. I might even see if i can pop it in someone else's rocket to test it out.

These are what I will use to build this::
GPS
Guide
Battery

Now should I use HC-05 or 06 because the guide uses 05 but 06 seems to be the same just a newer version?
HC-05
HC-06



Looks good! I will be using an HC-06. I'm waiting for Vance to drop a dime with some info regarding the programs and devices he uses with his setup.

IMPORTANT CAVEATS:

1) FOR BLUETOOTH: As I have not yet tested a mobile solution with bluetooth or with an OTG cable, I am not certain that either will work. This is why I'm antsy for a response from Vance. The ground radio plugged into my laptop using the programs U-center and VisualGPS gives me coordinates down to the dining room chair I'm sitting in, but I have not yet been able to tap into serial data on my ground 3dr radio. I'm at work right now, and haven't had time to mess around with it much yet. I wasn't interested in bluetooth anyway, but am providing what info I have discovered at no extra cost. Also, regarding bluetooth modules; Apparently some are sent with different pre-set baud rates. Be mindful of baud rates and that programming the module to match application baud rates may be necessary. Looks pretty easy but you will need an FTDI board. Lots of info online.

2) FOR OTG: I solder-bridged a jumper between pin 4 and pin 5 and made an OTG cable. It looks like **** though and I'm not sure I have good connections which is perhaps why I am unsuccessful with getting programs to work with OTG.

OR

Again, I suspect perhaps the android drone programs require some other data that would normally be sent from an air side 3dr that was plugged into an APM or other flight controller (PIXHAWK) in order to work properly. I don't know at this point. I have several actual OTG cables on order from ebay or gearbest or something and will report back when they arrive. In the meantime I'll keep working on finding some other android GPS program and let the forum know as soon as I am successful.

This is where I'm at right now.

---------------------------------------------------------------------------------------------------------------------------------------------------------

Edit: Also, don't forget to include the GPS antenna in your parts list :)

https://www.aliexpress.com/item/HAK...32799709822.html?spm=a2g0s.8937460.0.0.lWTIuU

And as for the battery, you may want to consider a larger capacity. The HC-06 consumes about 100mah, draining your battery in less than 3 hours if also used to power the ground radio. Maybe use something like this, I don't know, look around. Cheap LiPos are everywhere:

https://www.ebay.com/itm/3-7V-1500-...489809?hash=item28388d8211:g:rxUAAOSwhvFZJNRT
 
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Folks, while you are all trying to figure out the receive end, it remains that the receiver can still be plugged into a USB port of a laptop / tablet. One can still experiment with the system. Getting data out of a receiver wirelessly is the problem. It appears that the transmitter in some of these sets is actually a transceiver and can act as a receiver. Once someone troubleshoots a modification on a given system to use a B/T board to get the strings out of the receiver and into another device for processing, it will be very easy to follow those instructions.

The major advantage here would be for a higher powered tracking system in the 70 centimeter band AKA 433 megahertz but technically that's only open to ham radio licensees.

If one is truly apprehensive about trying to Cobble something together here, consider an EggFinder system and have someone build it for you. Unless of course you have the time and money to acquire the skills, if you don't already have them.

My major interest here is a higher-powered Tracker that is not APRS and is on a band that has better propagation characteristics. I haven't lost a rocket with a 900 megahertz tracker on board yet, but I would like to see better recovery of data positions while the rockets in flight. Increasing the power of the transmitter could improve this. I've noticed quite a few dropouts in the 900 megahertz band with live tracking on a map. I do have to emphasize that plenty of positions are received to effect a recovery though with a 100milliwatt, 900 megahertz tracker for sport rocket flying. Kurt
 
Just use this:

https://play.google.com/store/apps/details?id=googoo.android.btgps&hl=en

The program has everything you need to track. Rocket Locator works with NMEA by default, but you will need a network connection for plotting. I'm not sure why some people are so adamant about having a program plot a course from point A to point B for them. I guess the days of being able to read a map, figure out where you are and plot your own course are lost for some.

The HC-06 module is all you need for a BT connection. Just cut an old USB female cable and wire it up, pair with the application and that's it. But again, the radio and BT module will require power. My goal was to plug the 3DR receiver directly into my phone and not need any additional hardware. The Rx uses nothing for power, so I'm not sure why some are concerned with cell phone battery life. I would wager the apps most people don't know are running in the background suck more juice than an OTG radio receiver.

Quick correction here. You do not need a live network connection to plot on a map with GPS rocket locator. One can download Maps online for storage and can cache them for later use. The Google Maps link no longer works in GPS rocket locator. Unfortunately that's the default map set that gets called up when opening the program. One needs to go to the pull down in the upper right and select osm Maps. Again you do not need a live Network link for maps to work as long as you have downloaded the map tiles you need before going out in the field. This makes it simple for any Android device that has an on-board GPS to be used as a ground station. It's the device does not have an on-board GPS chipset you won't be able to get the GPS rocket locator to download.
You could even use an old cell phone that doesn't have active cell service as a device. As long as it has Wi-Fi one can download the map set and it Bluetooth is active you're in business. Kurt
 
m to use a B/T board to get the strings out of the receiver and into another device for processing, it will be very easy to follow those instructions.

The major advantage here would be for a higher powered tracking system in the 70 centimeter band AKA 433 megahertz but technically that's only open to ham radio licensees.

I ordered a 433Mhz version to play with. My concern is that as far as I know the 433 version is still FHSS. Even if you are a ham, I am not sure that a 100mw 70cm signal hopping around even a limited segment of the band would be neighborly at a launch. I do not know enough about 3DR radios to know if you can set the min-max frequency range tight enough to avoid stepping on a few mhz of 70cm frequencies.
 
I ordered a 433Mhz version to play with. My concern is that as far as I know the 433 version is still FHSS. Even if you are a ham, I am not sure that a 100mw 70cm signal hopping around even a limited segment of the band would be neighborly at a launch. I do not know enough about 3DR radios to know if you can set the min-max frequency range tight enough to avoid stepping on a few mhz of 70cm frequencies.

Would be interesting to see if it would interfere with the APRS Beeline trackers near frequency. Probably only minimally with the RDF trackers but perhaps
lost packets with APRS.

Still the issue with callsign ID but perhaps breaking in on frequency with an aural ID would be suffeicient. Kurt
 
My ground radio:

View attachment 324656View attachment 324657

It appears as though any soldering to serial leads may be impossible. This thing is way small!

I'm researching the radio specs now.


Check the pads at the top of the PCB on the close-up pic. I'll bet those are rx/tx/vcc/gnd. The two on the left look to be connected to the radio chip, they are probably data. The right is connected to the top plane, likely ground. Verify with a meter before connecting power/ground, use a FTDI cable, logic analyzer, bus pirate, etc to figure out the rx/tx.
 
Would be interesting to see if it would interfere with the APRS Beeline trackers near frequency. Probably only minimally with the RDF trackers but perhaps
lost packets with APRS.

Still the issue with callsign ID but perhaps breaking in on frequency with an aural ID would be suffeicient. Kurt

Thats not the only issue. Part 97 also requires of HAMS:
(3) Maintain a record, convertible to the original information (voice, text, image, etc.) of all spread spectrum communications transmitted.

Good luck with that.
 
Thats not the only issue. Part 97 also requires of HAMS:
(3) Maintain a record, convertible to the original information (voice, text, image, etc.) of all spread spectrum communications transmitted.

Good luck with that.

I could be wrong, but doesn't that apply only if deemed necessary by a District Director to assure compliance.
 
Your are correct, I looked that up after your reply.

Yeah, I suspect "ideally" a call in one of the strings would be desirous but I don't think anyone is going to soil their shorts if one comes on frequency and identifies what's going on. The only potential problem is if the NMEA tracker rocket drifts
away and is lost. In that regard, I don't think anyone is going to be monitoring for it, where we fly is out in the boondocks anyways and once a rocket is down the ground, the footprint is likely not more than 1 mile radius (as long as the rocket isn't
stuck in a tree or tower!) Plus the battery is going to die probably within a day.

Me not too worried about the receive end as like I mentioned a USB2.0 device is at hand for my purposes. One should be ready to put their receiving device in an open box the inside of which is painted flat black so you can position yourself to cut the
glare from the sun. At the last MWP I had my head buried inside the box in order to see rocket tracks.

With APRS tracking using a Kenwood or Yaesu VX-8GR interfaced with a handheld Garmin GPS of course the Garmins are designed to be read in direct sunlight. Computers/tablets/Android devices and most phones are not legible in
direct sun.

Once the rocket goes out of sight, one might as well see if they can get an in-flight position to develop a trend track on a mapping track. If the altitude is plotted one can know where to point their eyes to perhaps catch the main chute event. Be aware that a small rocket
like a Wildman Jr can be invisible on a 36 or 42" parachute a mile out. That is why I blow my mains no lower than 800 feet and sometimes higher depending on conditions. The higher altitude is better for Rf propagation and you will get to receive more positions
and see a better trend so once there's a loss of signal, you'll know which direction to proceed if you don't find the rocket at the last known position or you're not in the ground footprint to get a new live position.

Many just monitor the lat/long on their receivers and input that into a mapping GPS app/device. That works but the live mapping can give one a bit more of an edge for an aggressive flight that may come down a long distance away.
Kurt
 
They never drift away with a working tracker or GPS in the rocket.
 
They never drift away with a working tracker or GPS in the rocket.

Never say never.:wink::no::tongue: I just about lost one less than 100 feet away and I could hear the beeping of the NMEA receiver. That's when it occurred to stupidhead here to zoom in on the map!!
From now on, I'm going to cram in an aural screamer for the "terminal" phases of tracking!

In reality, I could foresee someone going stupid high stupid fast with a lower powered 100mW, 900Mhz GPS tracker and if they don't jump in their vehicle or dirt bike right away and/or if they are not doing real time
map tracking and just put the last known position into a GPS, they might end up at the last position out of the ground radio footprint and no idea where to proceed.

Granted most sport fliers aren't going to suffer this.:surprised: Kurt
 
Check the pads at the top of the PCB on the close-up pic. I'll bet those are rx/tx/vcc/gnd. The two on the left look to be connected to the radio chip, they are probably data. The right is connected to the top plane, likely ground. Verify with a meter before connecting power/ground, use a FTDI cable, logic analyzer, bus pirate, etc to figure out the rx/tx.

I was pondering that same idea. How convenient that there are four pads, right? Thanks for validating my thoughts! Do you think the tx/rx is before or after the ftdi chip? I haven't had a chance to look. At this point we know we need serial data for bluetooth.

Check this out:

https://api.ning.com/files/FmRNLe*vCpQ0LyKxuwR6vIkMuglkAXc79HR32AccvUi-VG5vCw*V5JUL3-BRT5*O*w8t7kti8fj73zaktIkCtN3izcq7BipF/3drschemat.png

And see page 34, here:

https://www.silabs.com/documents/public/data-sheets/Si1000.pdf
 
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I ordered a 433Mhz version to play with. My concern is that as far as I know the 433 version is still FHSS. Even if you are a ham, I am not sure that a 100mw 70cm signal hopping around even a limited segment of the band would be neighborly at a launch. I do not know enough about 3DR radios to know if you can set the min-max frequency range tight enough to avoid stepping on a few mhz of 70cm frequencies.

How many others do you know use 70cm at a launch? Is it usually that crowded where you fly? As far as I know, the range of frequency programming options span the width of the band. Here is a screenshot:

3drprog.png

Along with frequency selection, another advantage of this system is the ability to program the "NET ID", which is similar in function to channel settings, which as far as I understand is a protective function to prevent interference. Lots of programming flexibility, including TX output power adjustment.

Mission Planner screenshots with data:

https://www.google.com/search?q=mis...#imgdii=R7c9P3rcQ11CCM:&imgrc=0cGOf5ThwGIKPM:
 
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