Experiences with low cost M8N GPS modules?

[KDan]

About a week ago I installed a BN-800 GPS in my backup Solo. I thought that for under $18 it was worth experimenting with. I had hoped to get one of the V2 GPS shields from the 3DR store, but it seems they aren't available now. I ended up reusing the original one.
I also created a design for a 3D printed mounting bracket (uploaded to Thingiverse).
Someone else has a generic GPS mounting bracket for the Solo on Thingiverse, but it moves the GPS lower behind the battery, which can't be a good thing. My bracket keeps the GPS module at the same height and slightly more forward.

I've noticed that some other people have installed this GPS (or the seemingly identical RTFQ Mini8) in their Solos and have reported mostly good results.
I did not update the firmware or any settings in the GPS. I just spliced the new wiring harness into the original one. After about a half-dozen flights, my impression is also mostly good.
It definitely acquires satellites quickly, but seems to need a few more of them before Solo is happy with the HDOP and gives a ready for takeoff. It easily gets 12-14 on the ground, and then increases to around 20 in the air. It occasionally gets 21. The HDOP values peak at around 0.6 to 0.7.
Compared to the original REV B, it gets at least 6 more satellites. (most ever seen was 15 on REV B). The best HDOP on the REV B was 0.7, so not a big improvement there...
One thing I have noticed with the new GPS is that it seems to drift a bit more over time. Not an enormous amount, but perhaps 10 feet or so. The original REV B was usually only a few feet.

I'm curious what experiences other people may have had with these inexpensive GPS's - especially the RTFQ Mini8. Did you reflash the firmware or change any of the stock settings?

Yes, I know the mRobotics GPS is better, but it's also 4x the price of the BN800.

 

[xman4242]

How long does it take to acquire all the satellites needed for takeoff?
Also, how much faster is it that the Rev B?

 

[KDan]

Noticeably faster than REV B. Impossible to say how much faster because there are many variables involved. Also, some people - including myself - like to wait for an additional few satellites after Solo says ready for takeoff.
If I've just flown and am swapping out batteries for another flight, it typically comes up with the same number of satellites it had almost instantly.

 

[xman4242]

Noticeably faster than REV B. Impossible to say how much faster because there are many variables involved. Also, some people - including myself - like to wait for an additional few satellites after Solo says ready for takeoff.
If I've just flown and am swapping out batteries for another flight, it typically comes up with the same number of satellites it had almost instantly.

Ok. Thanks for the info[emoji3]

 

[Superman04p]

KDan ive been shouting that cheap gps units praises for weeks now... got mine off Amazon for like 20 bucks...18 to 20 sats everytime... alsi purchased a 2nd gps cable from ebay to have for original warranty purposes...full setup was cheaper than a rev b board

 

[nuggetz]

I got the mrobotics gps and tho it's not cheap the damn thing has been solid. Being able to use the original cable is a big plus too. Plug and play.

 

[jbrunel]

I've tried them all and its a lot of work but nothing beats the Here GPS on a mast. I get a lock 2 sec after waiting for solo ends with 15 sats .6 HDOP

 

[KDan]

I've tried them all and its a lot of work but nothing beats the Here GPS on a mast. I get a lock 2 sec after waiting for solo ends with 15 sats .6 HDOP

I think that putting any GPS on a mast is going to make a big difference on a Solo. The location of the stock GPS seems to be the cause of much of the issues.
I believe that 3DR let the styling take precedence over the engineering design. The GPS is too close to the electronics, and not located completely above everything that could partially block the GPS antenna view of the sky.
I've built DIY quad's with older Neo-7 modules that have much better GPS performance than the Solo. The difference is the GPS mounting location.

 

[pyrate]

at less than 50 bucks why mess with anything but the Here
that thing is awesome and looks badass

 

[KDan]

at less than 50 bucks why mess with anything but the Here
that thing is awesome and looks badass

I'm sure the same could be said of the mRobotics for $80. Why not just spend $80?
I'm just wondering if there is any discernible difference between the $18, $50, and $80 M8N options.

 

[BillHally101]

I'm sure the same could be said of the mRobotics for $80. Why not just spend $80?
I'm just wondering if there is any discernible difference between the $18, $50, and $80 M8N options.

I installed this in my Solo too and my expierience is much the same as yours 19 - 20 Sats locked very quickly for an HDOP of 0.6. I have been building multi copters for many years and agree whole heartedly with someones comment about 3DR's postioning being more cosmetic than functional. I did see your bracket on Thingyverse but decided to simply fit it using two of the existing holes and some heavy duty double side stick pad. There really is no substitute for getting the GPS away from other electronics and mounted higher this is where the Here GPS scores. Maybe some clever 3D programmer will design a folding bracket for this GPS unit the same as the one I have seen for the Here GPS that will get it away above and forward of the battery a little and at the same time is foldable to still fit the back pack.

Bill

 

[Pedals2Paddles]

The HERE unit is a phenomenal GPS and a compass. It replaces the stock GPS and it replaces the stock leg compass. Having the compass up on the mast moves it further away from the vehicle's electromagnetic crap. It also moves it away from magnetic anomalies in the ground. The GPS is basically the best you can get, it is also up and away from RFI. The LEDs on the HERE provide feedback on system status. So it is all around the best hardware. The guy who designed and built it is a former 3DR employee. He's also the guy that designed the Pixhawk 2.0 and the new new Pixhawk 2.1, that is basically the flagship of drone autopilots. Tech support is readily available here and on the facebook groups. His business (ProfiCNC) is responsive and on the ball. The trade-off is that it's externally mounted. You either love the AWACS look, or you hate it. it is slightly more vulnerable to mishandling and damage in a crash. You need to consider this when you buy. If you frequently crash, this may not be the product for you.

The mRO is a phenomenal GPS, very similar to the GPS in the HERE.. I It is the same form factor as the stock GPS, and mounts in the same place under the hood. This is the GPS the Solo should have had to begin with. It is plug and play. So if you prefer the sleek look/function, the mrRo is for you. The guy who designed and built it is a form 3DR employee that helped design the Solo. His small business selling this stuff is extremely responsive and helpful. Tech support abounds for those that need it through his business, here, and on the facebook groups.

The Drotek GPS is comparable to the mRO. But it is not plug and play. You will need to cut and splice wires. There is also no support here or in the facebook groups for that GPS. The manufacturer just doesn't. So you're kind of on your own with it. Given the price, this is obsolete since the mRo is plug and play, and fully supported here and on FB.

The cheap Chinese knockoffs are exactly that. They use inferior hardware, inferior assembly and soldering, and inferior child labor. There is little to no quality control. They use stolen and hacked firmware running on stolen and hacked hardware designs. They usually require custom wiring and changing connectors to marry up with the Solo. Do they work? People report success as you've seen in this thread and others. But you do not know what you're buying, and it could fail at any time. Or it could fail out of the box due to lack of QC. There is no tech support, no useful instructions, and nobody backing the product up. Basically, good luck.

The stock Rev A GPS is a steaming hunk of garbage. The engineers at 3DR didn't want to use it, but management forced it to save some pennies. It lacks the very basic and standard filtering. It has a useless copper shield that causes more problems than it solves. It can only use the American GPS constellation. And the almanac battery dies. All of this is why people sit there waiting for a GPS lock until the battery is too low for flight. It's an embarrassing mistake by 3DR's management.

The stock Rev B GPS is "acceptable". It has the filters that the Rev A didn't have. but it is still on the USA constellation only, old hardware, crappy battery, and not super accurate. It's leaps and bounds better than the Rev A, simply because you can actually take off and fly. But it's not a phenomenal GPS.

 

[kneel23]

yeah I have an original revA Solo which shipped in the first batch, and they take a long time to lock on. But this weekend I was flying it and it literally took less than 60 seconds each time, and when I would land to swap out batteries, it would always re-lock right away which is nice

So for me the US satellites alone are "usable" - I would replace it if I was using this particular Solo as a daily flyer or money maker. And if I did I would avoid the chinese knockoffs, simply not worth the savings.

Fired up my "Spare" solo this weekend to get some updates and setup done, and it must have the revB board as it locks on right away every time, no long waits. Safe to say I will be flying the "spare" solo from now on.

Now if only the batteries would hold a charge for more than 2 minutes

 

[cynfab]

Cheap "M8N" GPSs from e-bay, bangood, aliexpress fall into 4 categories:
1) those that use real u-blox M8N modules.
2) clones: (bn800 etc) that use the 8030 chip and add other parts to make a module that supports the ubx protocol, but may or may not have the correct size/type eeprom. (2.01 won't support Galileo and if the eeprom isn't right you can't update it)
3) counterfeits: usually have look alike "M8N" modules that are not real u-blox parts, they may or may not work alike. Many are based on the same circuit boards that were used for previous generations of u-blox modules Neo 6, Neo 7, etc, and may or may not have the Glonass compatible SAW filter that real M8N's should. (the 7020 and 8030 are pin compatible)
4) fakes: do not even use the 8030 chip so don't support ubx protocol.

I fitted my Solo with a bangood "M8N" module about a year ago. On the ground it worked great with good fast acquisition and 18+ sats. In the air it was very unstable. I attributed this to poor EMI resistance. I got an mRo as well as did some other GPS hacking ;>))

A close look at the original 3DR Solo's GPS reveals that the Neo 7N module is followed by an LNA and SAW filter. In the mRo, there is no such circuitry. THat's because u-blox added an LNA and SAW internally to the M8N module to improve its performance. So the mRo performs better than the original, even though the mRo uses the same GPS only antenna as the original. The antenna is wide band enough that it doesn't matter enough.

For those interested in learning more, read the u-blox user forum.
Recent questions - u-blox forum

Enough rambling... back to my cave...

 

[andrew.baker.142]

yeah I have an original revA Solo which shipped in the first batch, and they take a long time to lock on. But this weekend I was flying it and it literally took less than 60 seconds each time, and when I would land to swap out batteries, it would always re-lock right away which is nice

. So as long as you are in US its "usable" - I would replace it if I was using this particular Solo as a daily flyer or money maker. And if I did I would avoid the chinese knockoffs, simply not worth the savings.

Fired up my "Spare" solo this weekend to get some updates and setup done, and it must have the revB board as it locks on right away every time, no long waits. Safe to say I will be flying the "spare" solo from now on.

Now if only the batteries would hold a charge for more than 2 minutes

Remember, the "G" in GPS stands for Global. The stock Solo GPS will work as well in Africa as it does in the states. It's just called the US Constellation because the US launched the 29 satellites (28 plus one spare) into space, not that it only works in the US (unlike Sirius satellite radio).

 

[just_bruce]

The HERE unit is a phenomenal GPS and a compass. It replaces the stock GPS and it replaces the stock leg compass. Having the compass up on the mast moves it further away from the vehicle's electromagnetic crap. It also moves it away from magnetic anomalies in the ground. The GPS is basically the best you can get, it is also up and away from RFI. The LEDs on the HERE provide feedback on system status. So it is all around the best hardware. The guy who designed and built it is a former 3DR employee. He's also the guy that designed the Pixhawk 2.0 and the new new Pixhawk 2.1, that is basically the flagship of drone autopilots. Tech support is readily available here and on the facebook groups. His business (ProfiCNC) is responsive and on the ball. The trade-off is that it's externally mounted. You either love the AWACS look, or you hate it. it is slightly more vulnerable to mishandling and damage in a crash. You need to consider this when you buy. If you frequently crash, this may not be the product for you.

The mRO is a phenomenal GPS, very similar to the GPS in the HERE.. I It is the same form factor as the stock GPS, and mounts in the same place under the hood. This is the GPS the Solo should have had to begin with. It is plug and play. So if you prefer the sleek look/function, the mrRo is for you. The guy who designed and built it is a form 3DR employee that helped design the Solo. His small business selling this stuff is extremely responsive and helpful. Tech support abounds for those that need it through his business, here, and on the facebook groups.

The Drotek GPS is comparable to the mRO. But it is not plug and play. You will need to cut and splice wires. There is also no support here or in the facebook groups for that GPS. The manufacturer just doesn't. So you're kind of on your own with it. Given the price, this is obsolete since the mRo is plug and play, and fully supported here and on FB.

The cheap Chinese knockoffs are exactly that. They use inferior hardware, inferior assembly and soldering, and inferior child labor. There is little to no quality control. They use stolen and hacked firmware running on stolen and hacked hardware designs. They usually require custom wiring and changing connectors to marry up with the Solo. Do they work? People report success as you've seen in this thread and others. But you do not know what you're buying, and it could fail at any time. Or it could fail out of the box due to lack of QC. There is no tech support, no useful instructions, and nobody backing the product up. Basically, good luck.

The stock Rev A GPS is a steaming hunk of garbage. The engineers at 3DR didn't want to use it, but management forced it to save some pennies. It lacks the very basic and standard filtering. It has a useless copper shield that causes more problems than it solves. It can only use the American GPS constellation. And the almanac battery dies. All of this is why people sit there waiting for a GPS lock until the battery is too low for flight. It's an embarrassing mistake by 3DR's management.

The stock Rev B GPS is "acceptable". It has the filters that the Rev A didn't have. but it is still on the USA constellation only, old hardware, crappy battery, and not super accurate. It's leaps and bounds better than the Rev A, simply because you can actually take off and fly. But it's not a phenomenal GPS.

I'll tell you what, I'd pay a fair bit of money for a GPS module that was sorta located in the factory location next to the battery but could "pop up" on an extendable telescopic mast for those times when I'd like faster acquisition or more isolation from the EMI.

(Yes, I know, Have Cake & Eat it too. But a man can dream...)

 

[Pedals2Paddles]

The elevation helps the HERE's compass way more than it helps the GPS. If it even helps the GPS at all.

 

[andrew.baker.142]

I'll tell you what, I'd pay a fair bit of money for a GPS module that was sorta located in the factory location next to the battery but could "pop up" on an extendable telescopic mast for those times when I'd like faster acquisition or more isolation from the EMI.

(Yes, I know, Have Cake & Eat it too. But a man can dream...)

The Here GPS mount I made doesn't extend, but it is just held on with Velcro. I lay it down in the battery tray when transporting this Solo in the backpack. I made it high enough to get above the prop arc but not so tall that it wobbles around.

 

[skyhax]

Thanks for the tip on the cheap Amazon unit, ordered one. I have 2 REV a that can get 14 after doing massive shielding. The REV b never gets more than 10. That's even if it's swapped with a REV a install. All three go from 8-0 back to 8 sats in a tenth of a second. I just don't believe that's really even possible. Sometimes this is just sitting in the grass and the motors aren't even spinning. This is across three different refurb bodies.

 

[jbrunel]

I have the here gps and the $33 shipped Mini uBlox M8N both work well mounted outside the body with the edge going to the here for the pretty lights and no more searching for gps bs
Mini uBlox M8N GPS GLONASS W/ (35x35mm) Mounting backplane and Compass V2