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Nov 22, 2020, 12:19 PM
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Tean's Avatar
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Discussion

GEPRC Crocodile Baby


I'm a bit surprised there doesn't yet seem to be a thread for the Crocodile Baby so I'm starting one here.

It's usual for early buyers of a new product to rave about how wonderful their new toy is, but I'm going to have to break that mould with a bit of a grumpy harumph.

The Baby Croc looks to be fairly nicely built, apart from some motor screws that had not been tightened, and it seems to fly quite nicely in the limited time I've had it in the air so far, but the non-DJI version has a bit of a problem which Geprc have apparently fixed with a nasty and to me, unacceptable bodge.

Like many small FC/ESC combos the one supplied in the Baby has only two hardware UARTs, but it has three peripheral devices to talk to, the receiver, the GPS and the VTX. And so they have enabled a softserial port for the GPS. It seems a little strange to place the VTX on a hardware UART and the more data-intensive GPS on a software one, but I suppose it works ok. Except that the board is rather short of solder pads to connect the softserial port to, and this is where the nasty bodge has been done. The LED pad has been remapped to be the RX, and that's ok, but the TX has been directly soldered to the leg of a chip which I assume to be part of the current sensor because this has been disabled and its pin remapped to the softserial port. So we get a working satnav but at the expense of no fuel gauge. Thanks Geprc.

Perhaps I'm a bit old fashioned but I kinda think a fuel gauge is perhaps more important than a satnav and I think that at best this is a poor bodge, and at worst could even be considered rather dishonest as there's no warning of no current monitoring that I can find anywhere in Geprc's specs.


Fortunately there appears to be a solution to this although it requires some delicate soldering, which sort-of negates the attraction of a bind'n'fly. The attached picture shows the board as supplied in the Baby. The offending GPS wires are the white and green at the top, soldered to the LED pad and the leg of a component. Notice too the unused T1 and R1 pads beside the USB connector. The GPS can be moved onto these pads and its port changed to UART1. The VTX which uses UART1 as supplied, can be moved to softserial1, and this can be remapped to the LED pad. The VTX appears to be wired as one-way communication with only the TX from the FC being used. Once this is done the current sensor becomes unmolested and can be re-enabled on pin B01. The multiplier value of 210 given in the board spec sheet seems to be wrong but the value of 100 that is set in the Betaflight config gives credible readings. I have done all this and it all appears to work fine.

So hopefully I haven't bought a turkey and I'm looking forward to seeing how far it can go if I can only get some decent weather. It's been foul here lately.
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Nov 22, 2020, 03:39 PM
Registered User
Thank you for writing this. I spent considerable time deciding between Croc Baby, Chimera4, and Explorer LR. Chose the Chimera for the fc stack instead of an aio, but seem to have found myself in almost exactly the same boat as you anyway. Same issue with the gps on the spot needed for telemetry on the R9mm rx. I don't consider anything without telemetry to be a long range machine, but that is what the Croc/Chimera/LR is/should be. In your case it was the fuel gauge, in mine its the telem.

Its great there are people like you finding solutions to the problems presented by these manus not thinking things through properly.

In my case the solution may be there, but with no knowledge of remapping and no sign of any thread, info or discussion about the Iflight Success-E F405 mini fc anywhere, I have little hope of a fix.

Of course there is no Chimera4 thread yet either...
Had mine 2 days and its still on the bench.

May end up getting a Croc just to employ your fix and enjoy the quad the way it should have been when it left the factory!
Nov 23, 2020, 02:45 AM
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Tean's Avatar
Thread OP
Well I'm not familiar with the SucceX-E F4 but a quick look at the manual shows that it has six UARTs, so I can't see why you shouldn't be able to get everything to work. Can't you just use a different UART for the telemetry? Or if you're using Sbus/Smartport then they can share the same UART? Or you could use Fport on the R9mm in which case everything goes along the same wire?

And if you can't find a thread for the Chimera then you could always start one.
Nov 24, 2020, 01:13 PM
Registered User
I've had my Crocodile Baby for a couple of weeks now. I like it a lot - it flies very smoothly. But I'm having some problems with the GPS.

I accept that it is not the most accurate GPS. I armed the quad and let it sit for a couple of minutes while watching the altitude change from 0 to -10 feet to +25 feet and then go back down. There is no barometer, so the quad is entirely relying on GPS for altitude and I know that isn't very accurate, and for a "return to home" feature, if the altitude is off by a few feet, that's fine. I've also flown around and returned to the launch point and the GPS indicated it was 20 feet or more from home. Again, for a "return to home" feature, that is close enough.

The problem I have is that the "arrow" on the OSD (usually) does not point towards home. On my first test of RTH, the quad spun to point away from me (stopping in the direction the arrow had been pointing), ascended to 50m (the RTH altitude) and then started to fly AWAY from me. I took back over and brought it back safely. The second test it flew off at a 90 degree angle from the direction is should return. The third try did work. I've been doing a bunch of testing since then, and I can't get the arrow to consistently point to home.

I thought maybe the battery wire was too close to the GPS causing interference, so I attached the battery with the plug away from the GPS and stretched the cord across the top so it was as far from the GPS as possible (a bit hard since it attached to the flight controller on the GPS side). That did not change the results.

Other random thoughts ... The quad does not have a magnetometer. At least, it doesn't show up in Betaflight (I verified by re-watching the Bardwell video on this quad). So how does it know which direction is North? I don't think it uses the GPS magnetometer (if it even has one) I can't add a compass on the OSD (I guess that is not a feature supported by DJI FPV), but without a magnetometer, it probably wouldn't work anyway. I tried launching with the quad pointed north, which worked once, but then did not on subsequent tests.

Any ideas how to get the return to home arrow to work consistently?
Nov 26, 2020, 08:49 AM
Registered User
Smoothcruizer3's Avatar
Quote:
Originally Posted by Tean
I'm a bit surprised there doesn't yet seem to be a thread for the Crocodile Baby so I'm starting one here.

It's usual for early buyers of a new product to rave about how wonderful their new toy is, but I'm going to have to break that mould with a bit of a grumpy harumph.

The Baby Croc looks to be fairly nicely built, apart from some motor screws that had not been tightened, and it seems to fly quite nicely in the limited time I've had it in the air so far, but the non-DJI version has a bit of a problem which Geprc have apparently fixed with a nasty and to me, unacceptable bodge.

Like many small FC/ESC combos the one supplied in the Baby has only two hardware UARTs, but it has three peripheral devices to talk to, the receiver, the GPS and the VTX. And so they have enabled a softserial port for the GPS. It seems a little strange to place the VTX on a hardware UART and the more data-intensive GPS on a software one, but I suppose it works ok. Except that the board is rather short of solder pads to connect the softserial port to, and this is where the nasty bodge has been done. The LED pad has been remapped to be the RX, and that's ok, but the TX has been directly soldered to the leg of a chip which I assume to be part of the current sensor because this has been disabled and its pin remapped to the softserial port. So we get a working satnav but at the expense of no fuel gauge. Thanks Geprc.

Perhaps I'm a bit old fashioned but I kinda think a fuel gauge is perhaps more important than a satnav and I think that at best this is a poor bodge, and at worst could even be considered rather dishonest as there's no warning of no current monitoring that I can find anywhere in Geprc's specs.


Fortunately there appears to be a solution to this although it requires some delicate soldering, which sort-of negates the attraction of a bind'n'fly. The attached picture shows the board as supplied in the Baby. The offending GPS wires are the white and green at the top, soldered to the LED pad and the leg of a component. Notice too the unused T1 and R1 pads beside the USB connector. The GPS can be moved onto these pads and its port changed to UART1. The VTX which uses UART1 as supplied, can be moved to softserial1, and this can be remapped to the LED pad. The VTX appears to be wired as one-way communication with only the TX from the FC being used. Once this is done the current sensor becomes unmolested and can be re-enabled on pin B01. The multiplier value of 210 given in the board spec sheet seems to be wrong but the value of 100 that is set in the Betaflight config gives credible readings. I have done all this and it all appears to work fine.

So hopefully I haven't bought a turkey and I'm looking forward to seeing how far it can go if I can only get some decent weather. It's been foul here lately.
I'm now interested indeed, have you made any adjustments to the board? Is the previous or outta box wiring still legit to fly? I have one on the way, also will the vtx have enough power to be able to supply the full 600 mw? Thanks
Nov 26, 2020, 01:14 PM
Registered User
Tean's Avatar
Thread OP
I had my first proper outing with the Croc Baby today. I have the 4k analogue version with a Crossfire receiver. Battery was an 18650 pack made from VTC6 cells, 3000mAh capacity and 210g, probably the same cells as the Geprc pack. Some reviewers have seemed unsure whether the battery is included with the Croc but mine came without one.

Previous test flights have been with a 4s 1050mAh lipo pack of about 100g (TBS Gemini pack) and the extra weight of the 18650 was very noticeable but the Croc didn't ever seem to struggle with it. I wouldn't want to acro it with the heavy pack but it can manage 'spirited' flying about ok.

The GPS takes a little while to find satellites but it managed up to 22 of them once it got a fix. I didn't test rescue mode but the direction to home arrow seemed to stay surprisingly accurate considering there is no mag.

Overall I enjoyed the flying experience and was surprised how well it handled the wind which was about 10 knots or so. There is some pitch twitching on the HD recording and the motors can be heard twittering, usually just after a wind gust has disturbed things. I think it's just the PID gain is a little high and will try with it turned down a bit next time. I couldn't see it through the FPV camera.

The Caddix Tarsier HD camera seems to make quite nice pictures. The recordings not surprisingly look very compressed and you won't get good still grabs from them but they generally look ok when playing. The FPV camera is terrible though. I don't have wide experience with lots of FPV cameras but compared to the various Swifts I use in other models the Tarsier is just horrible. As a viewfinder for the HD it might be just about tolerable but for enjoying the view while you fly it's just awful.

The VTX/antenna seemed to work as expected. On 25mW it goes out to a few hundred meters ok. I bumped it up to 200 and it got a bit cleaner. I didn't feel the need to try 600 on this flight. This is the first model I've used Crossfire with a horizontal antenna in. The dead spots off the ends are really noticeable and I will be looking to get a vertical install done before I try to push the range at all.

With my modified resource mapping everything seemed to work fine. All the reviewers I've seen have been using DJI and no-one has mentioned any problems so I assume that the current meter problem only applies to analogue versions.

All in all, a good first outing, except for the FPV camera. I flew for about 15 mins before my hands started getting cold and that used about half of the battery.
Nov 26, 2020, 03:26 PM
Registered User
Congratulations on your successful remapping . Good to know about the batts, I have the same, also the camera (won't be getting one now). You are really making me consider ordering a Croc Baby...

My remapping attempt has so far failed, and I wonder if my board is even capable of telemetry.
Dec 03, 2020, 12:46 PM
Registered User
Flying Potatoes's Avatar
Just ordered a Tarsier version for my son. I see the gps is now on top of the battery - is this how it's been from launch? I thought it was out back like the Explorer etc.

Edit: revisited Geprc website. Tarsier version is the only one showing strap mounted gps. Guess this is down to the rf interference from split type cams. It's what I did with my turtle v2 / 5"lr.
Last edited by Flying Potatoes; Dec 03, 2020 at 12:54 PM.
Dec 03, 2020, 01:03 PM
Registered User
Tean's Avatar
Thread OP
The first ones had the GPS out on the back bumper but mine came with the it on the battery strap. It seems sensible as it has a better view of the sky and the battery acts as shielding, but it makes it a bit of a faff to strap the battery on, especially if you want to swap between the big 3000 lion pack and smaller lipos.

Many people seem to find the GPS on these micro long range jobs is a bit crap. The Diatone actually comes with it disabled and the Flywoo apparently doesn't work half the time, but I have to say the GPS on my Croc Baby seems to work just fine, always finding plenty of sats within a minute or so of switch on. Maybe it's the strap mount that makes the difference.
Dec 03, 2020, 01:58 PM
Registered User
Flying Potatoes's Avatar
Quote:
Originally Posted by Tean
The first ones had the GPS out on the back bumper but mine came with the it on the battery strap. It seems sensible as it has a better view of the sky and the battery acts as shielding, but it makes it a bit of a faff to strap the battery on, especially if you want to swap between the big 3000 lion pack and smaller lipos.

Many people seem to find the GPS on these micro long range jobs is a bit crap. The Diatone actually comes with it disabled and the Flywoo apparently doesn't work half the time, but I have to say the GPS on my Croc Baby seems to work just fine, always finding plenty of sats within a minute or so of switch on. Maybe it's the strap mount that makes the difference.

The unit itself also makes a difference. I built my Dave_C 5" lr with a TBS M8 which always struggled for a lock, so swapped it out for a Bn880 which, though enormous, works a treat. Strap mounted.
Dec 03, 2020, 02:34 PM
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Flying Potatoes's Avatar
I see Hobbyrc now have a new M8.2 with flash memory. Might grab one.
Dec 03, 2020, 02:41 PM
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Flying Potatoes's Avatar
Need to get some spare props. Any thoughts on these?

https://droneauthority.co.uk/collect...ade-propellers
Dec 04, 2020, 05:41 AM
Registered User
Tean's Avatar
Thread OP
They look more bull-nosed than the stock Gemfans. Perhaps a bit more thrust and a little less efficiency?

I've not generally been a lover of Gemfans in the past but I am impressed by the balance of these ones. No jello whatsoever on the HD recordings with a hard mounted camera.
Dec 04, 2020, 07:38 AM
Registered User
Flying Potatoes's Avatar
Quote:
Originally Posted by Tean
They look more bull-nosed than the stock Gemfans. Perhaps a bit more thrust and a little less efficiency?

I've not generally been a lover of Gemfans in the past but I am impressed by the balance of these ones. No jello whatsoever on the HD recordings with a hard mounted camera.
Thanks for that. I couldn't find UK stock of the stock props.
Dec 23, 2020, 05:08 PM
making crashing a lifestyle!
dutchcommando's Avatar
i've had ordered a crocodile baby HD (digital) but had gotten a 4K (analogue) version by mistake of the (Chinese) vendor.
after contacting the vendor, he told me he would be willing to send me a separate vista, but they weren't in stock anymore and he couldn't get new stock at that moment. so he told me he gave me two options:
1: i'd send back the 4K croc and he would send me a I-Flight Chimera4 digital.
2: he send me an DJI air unit.

now sending back the baby croc to china is way to expensive, so i took my loss and agreed to get a (free) air unit.
so now i had a crocodile baby with analogue setup but i wanted it to be digital..
so i took out the Caddx Tarsier V2 and the vtx and started designing a mount for the air unit, and whilst i was at it designed a new tail that would house the two antennas, the gps and the buzzer. i couldn't help myself, so i made a new nose to so i could use my insta360 Go camera if i wanted to..

now i have a crocodile baby with DJI air unit and onboard HD recording that weighs only 11 grams more than the 4K version!

i did not like how the AIO fc/esc was sitting inbetween the carbon of the arms since the esc wires/solderpoints were to close for comfort next to the arms.
so i just flipped the frame upside down. it's not needed to fit the air unit in, but it's just for my ease of mind.

if anyone want to convert their analogue baby croc to an air unit here are the files:

https://www.thingiverse.com/thing:4689740


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