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Quectel L80

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Should we switch to Quectel L80 because of the problems with the other one? (Problem shown above)

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  • no

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Hello, thank you for paying attention. We are trying to switch to Quectel L80 GPS module from GY-NEO6MV2 for our rocket. The rocket will be a 1500m sounding rocket. GY-NEO GPS module has us worried because it doesnt easily connect to the satelites (At least in our experience so far.).
Our questions are:
Would the Quectel L80 require a PCB to use with Arduino MEGA?
Would the library we are currently using (TinyGps++) work with Quectel L80?
 

mikec

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I'd think you would have better luck with the NEO6, which uses a Ublox GPS receiver. I can't tell what type of receiver the L80 uses. What problems are you have with the NEO6? I assume you are outside, with a good view of the sky, antenna pointing up, etc? I've had really good luck with Ublox receivers.

Assuming they send standard NMEA strings, all GPS modules should be roughly compatible.

The L80 is a module and would need some kind of breakout board to use.
 

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A month or more ago at our university campus during night time NEO6 module (that we never dropped btw) didn't connect to the satelites for 2 hours (then we gave up). The only thing that was obstructing the sky was the cafeteria building in front of us. But 3 other sides and above us were open.

The module doesn't always connect to the satelites easily and we have an upcoming contest. This is the problem we are having with NEO6. We dont want to go there and have problems.

If you could suggest any other GPS module to use instead, that would be much appreciated.
 

UhClem

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The NEO6 is an all in view receiver and its time to first fix even for a cold start is about 30 seconds. Any longer than that and you have a problem. It could be a poor antenna, ESD damage to the GPS chip, or something else.

Note that the antenna pins of GPS receivers are especially ESD sensitive so you should never touch the antenna except in an ESD safe work environment.
 

mikec

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I agree with David, you most likely have a bad module. I've used very similar modules to the GY-NEO6MV2 in rockets and they work great and lock up quickly.

Does it send empty NMEA strings when it's not locked up? If it just doesn't send anything it's probably dead or you have the baud rate wrong.
 

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My friend experimented with module yesterday and successfully read data from it at his balcony. When he got back to his room though the module disconnected and reconnected after a bit. I guess we were just unlucky for whatever reason. That night the module wouldn't connect to any satelites for 2-3 hours. Thank you all so much for your replies we decided to stick with NEO6 but really would appreciate further information about the module such as the battery inside it.
 

g.pitts

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My friend experimented with module yesterday and successfully read data from it at his balcony. When he got back to his room though the module disconnected and reconnected after a bit. I guess we were just unlucky for whatever reason. That night the module wouldn't connect to any satelites for 2-3 hours. Thank you all so much for your replies we decided to stick with NEO6 but really would appreciate further information about the module such as the battery inside it.
My experience in the design of systems is that if you have issues that magically disappear without understanding their cause, they will magically reappear at an extremely inconvenient time - like the day of your launch. The advice you've been given is wise: get another module. I would add one thing to that advice: put a mark on top of the suspect module with an indelible marker so that you do not mix up the two!
 

mikec

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To be clear, we are suggesting that you get another module of the same type.

If the battery is installed, it will hold the module's state for some time (days to weeks, maybe?) when power is off. It charges in circuit. You don't need it if you don't cycle power in flight, but it will speed up the start time if present.
 

jderimig

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The Quectels use an MT3339 chipset, which is very solid. It should have ephemeris backup with a battery or the option for that. If it does make sure you are using that option. Cold boots should take ~5secs in that case. If you are still having issues it may be the antenna or its connection has a problem. You can hook the module to ublox ucenter program and see what the signal strengths are as it starts acquiring a lock. Outside you S/N for each satellite should be above 30. If not, replace the module.
 

mikec

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The Quectels use an MT3339 chipset, which is very solid.
Solid on the ground, certainly. FWIW, I've had several experiences with Mediatek chipsets freezing in flight and reporting the same position even after being moved, so I'm not flying anything except Ublox any more. YMMV.
 

jderimig

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Solid on the ground, certainly. FWIW, I've had several experiences with Mediatek chipsets freezing in flight and reporting the same position even after being moved, so I'm not flying anything except Ublox any more. YMMV.
The MT3339 have different dynamic modes that need to be selected by their binary protocol just like uBlox. The have a terrestial mode and 2 dynamic modes.
 

mikec

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The MT3339 have different dynamic modes that need to be selected by their binary protocol just like uBlox.
Do you actually have flight experience with the MT3339? I tried those and they didn't seem to help.

At any rate, absent any compelling reason to use something else, I'd stick with the flight-proven ublox.
 

jderimig

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Do you actually have flight experience with the MT3339? I tried those and they didn't seem to help.

At any rate, absent any compelling reason to use something else, I'd stick with the flight-proven ublox.
Hmm, very limited, but I flew some last year, no issues. But I agree ublox is good. The MT3339 does have a balloon-mode which supposedly unlocks altitude to 80Km which makes it somewhat intriguing.

Are you sure you flew the MT3339? Mtk has some different modules, MT3337 is more popular.
 

mikec

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Are you sure you flew the MT3339? Mtk has some different modules, MT3337 is more popular.
Pretty sure. https://www.adafruit.com/product/790 But going back and checking, I'd have to admit that I wasn't changing the dynamic mode, just the DGPS and SBAS modes. I actually can't find any documentation that even describes the dynamic modes, don't see it in https://cdn-shop.adafruit.com/datasheets/PMTK_A11.pdf

At any rate, having the module freeze in normal mode really eroded my confidence in it, so I went to U-blox once the integrated-antenna SAM-M8Q came out, and those have been much more solid for me.
 

jderimig

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Pretty sure. https://www.adafruit.com/product/790 But going back and checking, I'd have to admit that I wasn't changing the dynamic mode, just the DGPS and SBAS modes. I actually can't find any documentation that even describes the dynamic modes, don't see it in https://cdn-shop.adafruit.com/datasheets/PMTK_A11.pdf
That page does not have the latest PMTK release. For others this using this module, the dynamic mode settings can be found in this document, page 22.
https://cdn.sparkfun.com/assets/parts/1/2/2/8/0/PMTK_Packet_User_Manual.pdf
 
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