GPS mod (Some may say upgraded)

[Mode-S]

Ref: 22 Satellites with a HDOP of 0.5

Hi,

First of I have to say I never had any issue with the stock GPS unit as I fly my Solo generally in locations the u-blox Neo-7 series was designed for (rural and sub-urban areas) but I did think to myself... a better GPS unit can easily be designed and be a like-for-like replacement. So I powered up my PCB (printed circuit board) design program and started clicking away.

After a few hours that afternoon I had a new board designed - Sweet!

I sent the PCB files of to be made and started ordering the components I selected in the design so when everything gets delivered i can populate and reflow the board.

OK, a basic run down of the design... I selected the U-Blox NEO-M8U because it had the ability of out putting GPS data in a dead reckoning (Internal navigation system) scenario due to bad GPS reception and it had dual reception paths to allow simultaneous GPS and GLONASS - unlike the stock GPS with can only do one or the other. The next thing I had to pick was a low noise amplifier (LNA) and pass band filter (SAW) because the NEO-M8U didn't have an "in built" LNA, I picked a nice one which combined both an LNA and SAW.

Antenna? well I had to get one that fitted in the small space 25x25cm so their wasn't that many to select from but i did find one with better gain then the one that comes with Solo.

One other thing I did was brake out the USB port from the NEO-M8U so I could use u-block software directly into the unit.

Well whats the conclusion? Me likely, I get so many more GPS/GLONASS and with a ready to fly in under a minute from a cold start is always a great thing. At start of flight I have about 13 Satellites but as I fly it picks up more and I've had up to 22 Satellites with a HDOP of 0.5 by the end of flight.

The only thing I would change is the backup power from a rechargeable battery to a supercap, the battery option is not really the best solution for how the GPS unit is used.

-I've attached some photos and design file under the open source licence, the design files are from a program called Diptrace (for the size of this design it is free)

-The attached screen shot image is a side-by-side test between the stock GPS (NEO-7N) and the NEO-M8U inside my home. Stock GPS is top, replacement GPS/GLONASS one is botton

 

[Jubalr]

Welcome to the forum. Very impressive MR. S. Nice clean layout. What was the total cost of parts involved? Does it make sense to offer as a plug-n-play solution?
With your handle, I assume an aviation electronics background?

Having been here from the beginning, I have to say that this needs an award as best First Post Ever....

 

[Dmitry]

settings in the configuration view?

 

[Pedals2Paddles]

Definitely the most epic first post. Some newb will need to build a JATO module to top this one. Or maybe find a box of Sony cameras and gimbals that fell off a truck for sale on eBay.

 

[Mode-S]

Welcome to the forum. Very impressive MR. S. Nice clean layout. What was the total cost of parts involved? Does it make sense to offer as a plug-n-play solution?
With your handle, I assume an aviation electronics background?

Having been here from the beginning, I have to say that this needs an award as best First Post Ever....

Thanks,

I went with the plug-n-play solution because the way i saw it I had two options,
1-replace the GPS unit on the stock PCB or
2-made a new PCB.

As it was only going to be a few dollars more for a new PCB i went with that, no need to modify the original if i didn't have too. The total cost was around $75 - the most expensive thing was the GPS unit its self because I only wanted two. I payed $59 each NEO-M8U (if you get 100 the unit cost goes down to about $20) all the other parts were minimal.

Cost run down....

GPS (NEO-M8U) = 59
Antenna = 5
LNA = 1
Voltage Reg (Low noise) = 1
USB connector = 0.75
Connector for Solo = 0.65
other passive components = 0.5
PCB = 6 (only because i did immersion gold finished, you can get it cheaper with a HAL finish) - the total cost was $65 for min order of 10 PCB, well the min is 5 but 10 is the same price so you might as well go 10
Total = $73.90

Yes I do have a avionics background, I've worked in the maintains/engineer area in different forms over the years (about 14 years)

settings in the configuration view?

You can pull the GPS data from solo if you wish but solo's not happy with it (don't try and fly when doing it)

To connect to the GPS via Wifi follow these instruction (option #1) once your connected you need to change the protocol out from " 0 -UBX " to " 0+1 - UBX+NMEA " under the flowing configuration tree UBX>CFG>PRT

Once done click "send" at button right, If you DON NOT change anything else the config is temporary and a reboot will set things back to default.

After you make this change the Ublox U-Center program will display satellite information from Solo's GPS unit

 

[RichWest]

Yep, impressive work and thoughtful consideration for the battery and usb.

Any consideration to have mounted the antenna on a mast, say by 2-3" above the bird?

 

[fpvsteve]

great work!
You may further improve GPS by using the new V2 shield provided by 3DR. Attenuation is significantly better than copper or aluminum.
Also you may enable Galileo in addition to Glonass.
I am getting up to 25 sats at a HDOP <0.5 with my m8 mod.

 

[n01kn0ws]

Very... very nice!

Maybe U can contact spektreworks for making this a more wide open for buying to solo users?

 

[SARDG]

First posts are traditionally problems with, or complaints about, Solo - with no detailed info attached to help the poster out if we wanted to.

@Mode-S, you need to go back to First-post School.

 

[cynfab]

Mode-S,
Very nice.
I always wanted to do a GPS board, but I've too many irons in the fire. Are you thinking of producing your boards or maybe doing a group buy of the hard to get components.
Good choice of the u-blox M8U. As it is targeted for the Automotive market, it will be a cheaper option than other versions. And the Automotive market is VERY picky about safety so the UDR stuff should be first rate. I also like the combined LNA/SAW as well as the ferrites on Tx & Rx lines.
I'd also be interested in where you sourced the u-blox M8U module.

A Big Thanks for sharing your work.

 

[Perry Lawrence]

Great work and awesome first post. May I suggest you join forces with Jordi Muñoz at mrobotics. He is beta testing his version here:

mRo GPS u-Blox Neo-M8N (Early release)

(75 units sold out in 48 hours)

 

[cynfab]

Mode-S,
I think your schematic has a parts value error. C6 & C7 should probably 20nF not 20pF.

 

[Mode-S]

Yep, impressive work and thoughtful consideration for the battery and usb.

Any consideration to have mounted the antenna on a mast, say by 2-3" above the bird?

Nope, not plan on mounting an antenna on a mast. I'm going form over fictions on that one as I don't see any real advantage.

great work!
You may further improve GPS by using the new V2 shield provided by 3DR. Attenuation is significantly better than copper or aluminum.
Also you may enable Galileo in addition to Glonass...

The aluminum shield works more like a faraday cage then attenuation any signal, I've exposed the ground plan around the mounting hole as to have a contact for the shield when mounting it in Solo.

The unit is designed to work with all four GNSS systems, GPS/GLONASS/Galilieo and BeiDou. I just didn't enable Galilieo or BeiDou because I thought they were not operational yet?

Very... very nice!

Maybe U can contact spektreworks for making this a more wide open for buying to solo users?

I did think about making it available to buy but there is one thing that stops me, postage cost to the consumer. As I live in Australia the postage cost for the finish unit to the rest of the world would add a large amount of additional cost, it would be just as much if not more then the GPS unit itself.

Mode-S,
... I'd also be interested in where you sourced the u-blox M8U module...

I got then direct from u-blox, they have a online store. I did read you can get cheap ones else were but there are counterfeit unit out there...

Mode-S,
I think your schematic has a parts value error. C6 & C7 should probably 20nF not 20pF.

20pF is correct, C6 & C7 are for high frequency decoupling of in-band noise in the GNSS band which may(or may not) find itself on the power rails.


.

 

[fpvsteve]

The aluminum shield works more like a faraday cage then attenuation any signal, I've exposed the ground plan around the mounting hole as to have a contact for the shield when mounting it in Solo.

The unit is designed to work with all four GNSS systems, GPS/GLONASS/Galilieo and BeiDou. I just didn't enable Galilieo or BeiDou because I thought they were not operational yet?

Yes, but with the V2 shield it will be even better - trust me, I tried all the options already
Beidou makes only sense in greater China region. Galileo is operational with its first 4-5 satellites. With my Solo it usually gives me 1-2 sats and ~0.1 in hdop in addition to GPS and Glonass.

 

[cynfab]

Mode-S,
Thanks for the pointer to the u-blox online store, I had never seen that before on their site...
And thanks for the pointer to diprtrace, it works under wine and I can import your pcb design file as well as the schematic.
I'll take your word on the 20pF caps, noise management in GNSS receivers is somewhat of a black art...

 

[n01kn0ws]

Maybe you can hook up with spektreworks or currentuas to make this available to the solo owners?

 

[SurfnSkate81]

Nope, not plan on mounting an antenna on a mast. I'm going form over fictions on that one as I don't see any real advantage.



The aluminum shield works more like a faraday cage then attenuation any signal, I've exposed the ground plan around the mounting hole as to have a contact for the shield when mounting it in Solo.

The unit is designed to work with all four GNSS systems, GPS/GLONASS/Galilieo and BeiDou. I just didn't enable Galilieo or BeiDou because I thought they were not operational yet?



I did think about making it available to buy but there is one thing that stops me, postage cost to the consumer. As I live in Australia the postage cost for the finish unit to the rest of the world would add a large amount of additional cost, it would be just as much if not more then the GPS unit itself.



I got then direct from u-blox, they have a online store. I did read you can get cheap ones else were but there are counterfeit unit out there...



20pF is correct, C6 & C7 are for high frequency decoupling of in-band noise in the GNSS band which may(or may not) find itself on the power rails.


.

@Mode-S I'm on the Gold Coast, I'll buy two if your selling?


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[Cyberblitz]

I live in Brisbane, I'll buy two too.

 

[Mode-S]

Hi all,

Once I figure out the best approach for a issue with the design I'll see what the cost is going to be for a small patch run so people can get they hands on one(or two).

All right what is the issue? its nothing that is going to affect the normal operation of the unit or solo but has to do with the untethered Dead Reckoning (DR) side of the unit, two things

1. When dead reckoning is enabled and the GPS unit has a fix of 3D+DR (GPS fix + Dead Reckoning) solo indicates this as a GPS fail, I assume this is something to do with the software code of Solo itself because of an unknown GPS fix indication.

2. If I do go down the line of making the dead reckoning side fully functional a better backup power supply is needed to hold the calibration data for dead reckoning while off, other wise it needs to self calibrate even time you use it and what I have read from the manual this take some time - basically making the dead reckoning function pointless for a UAV application due to the flight time of the typical UAV.

I just need to find a battery with at lest 400mhA of capacity (looking for a 3 year life or more), fits within the board and is surface mount - haven't had any luck finding a battery of battery mount/clip.


In saying all this if you disable UDR the unit work perfectly fine with Solo.

 

[SurfnSkate81]

If dead reckoning is something Solo doesn't have now I doubt it would be vital if we aren't already using it. But if this is something that you can implement fairly easily then go for it.

I know that most people interested just want the GPS to acquire lock faster and be more reliable by using Glonass and GPS. This is an improvement over what we already have and would be what the market wants, anything else you can add that is still cost effective to produce then go for it but keeping it simple would still have people lining up for your improved GPS.


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