GEPRC Nano ELRS RX Randomly Bricked (Tentative???) | ExpressLRS Community | Page 1

covert mortar Jul 18, 2023, 7:48 AM

#

I currently have a geprc nano elrs rx (on UART 2) which was working perfectly. Suddenly, one day, it just randomly "soft bricked" itself, and the light is a solid blue from power up of the quad. Whenever I unplug my vista (which is on UART 1) and power on the quad, the rx is "unbricked", and binds fine with my radio, and is working properly. However, when I plug the vista back in, the rx stops working again, and bricks itself. The vista harness already has the extra ground and sbus wire detatched, so im not sure why the vista is affecting the elrs rx, even though they're on completely different uarts. any help would be much appreciated!

tribal robin Jul 18, 2023, 7:49 AM

#

covert mortar I currently have a geprc nano elrs rx (on UART 2) which was working perfectly. S...

can you post a photo of the wiring? are you certain it's the SBUS wire that was dettached?

#

because that's the only explanation I got for you..

you said that with the vista disconnected, it works properly.. connecting the vista makes it stop working

covert mortar Jul 18, 2023, 7:57 AM

#

tribal robin can you post a photo of the wiring? are you certain it's the SBUS wire that was ...

the sbus wire on my vista isn’t even connected

tribal robin Jul 18, 2023, 7:57 AM

#

covert mortar the sbus wire on my vista isn’t even connected

and you're sure that the rx and tx isn't in the same uart?

#

could you try moving the receiver into a different uart?

covert mortar Jul 18, 2023, 7:58 AM

#

tribal robin and you're sure that the rx and tx isn't in the same uart?

yep. the vista is on uart 1, per the plug port on the fc. and the rx is in uart 2 (and i can control all switches and arm if i disconnect the vista)

covert mortar Jul 18, 2023, 7:59 AM

#

tribal robin could you try moving the receiver into a different uart?

the current board i’m using only has uart 1 (for the vista), uart 2, and uart 5 (for the gps which is being used)

tribal robin Jul 18, 2023, 7:59 AM

#

covert mortar the current board i’m using only has uart 1 (for the vista), uart 2, and uart 5 ...

swap uarts with gps

covert mortar Jul 18, 2023, 7:59 AM

#

i’ll give that a shot

tribal robin Jul 18, 2023, 7:59 AM

#

gps goes to uart2
receiver goes to uart 5

covert mortar Jul 18, 2023, 8:11 AM

#

tribal robin swap uarts with gps

i just swapped them, same thing

#

solid blue light when vista is plugged in, blinking to connect when vista is unplugged

tribal robin Jul 18, 2023, 8:12 AM

#

that is certainly weird..

#

you're using a plug to connect the vista into the fc? were all wires still in the plug?

covert mortar Jul 18, 2023, 8:15 AM

#

tribal robin you're using a plug to connect the vista into the fc? were all wires still in th...

yes. all wires in (besides the ground and sbus for dji tx)

tribal robin Jul 18, 2023, 8:17 AM

#

covert mortar yes. all wires in (besides the ground and sbus for dji tx)

then it's not all.. only 4..

#

can you inspect whether the sbus and gnd pins are touching or shorting out in any way please..

covert mortar Jul 18, 2023, 8:19 AM

#

tribal robin can you inspect whether the sbus and gnd pins are touching or shorting out in an...

#

they look fine to me

tribal robin Jul 18, 2023, 8:20 AM

#

covert mortar they look fine to me

and the vista works fine?

covert mortar Jul 18, 2023, 8:21 AM

#

tribal robin and the vista works fine?

yep. i get video, and my wtfos shows up

#

no issues there

tribal robin Jul 18, 2023, 8:22 AM

#

weird..

first time I encountered this..

#

which FC is it?

covert mortar Jul 18, 2023, 8:22 AM

#

yeah i’m not sure either. it also worked previously, and then just now decided to not work

#

span f722 bt hd v2

#

from geprc

tribal robin Jul 18, 2023, 8:27 AM

#

what if you solder the wires from the vista instead..skip the plug?

#

(unsolder the wires from the vista, and use a different set of wires so you still have the plug for later)

covert mortar Jul 18, 2023, 8:28 AM

#

hmm

#

i can give that a shot

covert mortar Jul 19, 2023, 4:22 AM

#

tribal robin what if you solder the wires from the vista instead..skip the plug?

so i just tried it again

#

i first swapped out the dji harness and used another one

#

plugged the vista into the fc, powered on, and it worked!!

#

and then like 5 attempts later, the rx softbricks again

#

so i took out the plug and soldered directly on

#

still soft bricked

#

works if i remove the vista

#

i don’t get why it works in the beginning a few times, and then stops working

tribal robin Jul 19, 2023, 4:24 AM

#

I don't get why it shouldn't work at all with the vista plugged in..

covert mortar Jul 19, 2023, 4:24 AM

#

yeah i don’t get it zz

#

sbus isn’t connected, i can clearly see vista is on uart 1, rx is on uart 2, gps is on uart 5

tribal robin Jul 19, 2023, 4:25 AM

#

try connecting a pull-up on the receiver's uart RX pad

covert mortar Jul 19, 2023, 4:25 AM

#

uhh, not sure what that means

tribal robin Jul 19, 2023, 4:27 AM

#

https://www.expresslrs.org/assets/images/pull-up.png

covert mortar Jul 19, 2023, 4:28 AM

#

is that something i need to buy?

tribal robin Jul 19, 2023, 4:28 AM

#

covert mortar is that something i need to buy?

the resistor, if you don't have any with those values

covert mortar Jul 19, 2023, 4:29 AM

#

#

one of these?

tribal robin Jul 19, 2023, 4:30 AM

#

covert mortar one of these?

yes

covert mortar Jul 19, 2023, 4:32 AM

#

so one side connects to the rx pad on my fc? where does the other side connect to

tribal robin Jul 19, 2023, 4:32 AM

#

covert mortar so one side connects to the rx pad on my fc? where does the other side connect t...

a 3.3v pad.. or a 5v pad

covert mortar Jul 19, 2023, 4:33 AM

#

hm ok. i’ll give that a try

#

https://geprc.com/docs/why-geprc-elrs-rx-is-always-on-and-can-not-work-when-powered-it-up/

GEPRC

maxiulian

Why GEPRC ELRS rx is always on and can not work when powered it up?...

Recently, many users have reported that some F4 flight control Uart 2 ports are wired according to the crsf receiver in the manual, and the ELRS receiver is always on and can not work. After data inquiry and test, it is determined that for the receiver with ESP chip, if the TX interface is placed [...]

#

so i found this

#

but i dont get why it would work in the beginning a few times, and then stop working

#

also, i just tried this: i unsoldered the rx and tx pads for the vista, so only the ground and 12v are still connected

#

and the rx is still soft bricked

#

even though the uarts for the vista are now open

tribal robin Jul 19, 2023, 4:45 AM

#

it could be the power pull on the fc..

#

even the document you posted suggest the pull-up

covert mortar Jul 19, 2023, 4:46 AM

#

gotcha

#

is it safe to solder the pull up to a 5v?

#

or does it need to be 3v3?

tribal robin Jul 19, 2023, 4:48 AM

#

if you have 3.3v, then it's best to use that.. because the logic levels on the chip is 3.3v

if you will use 5v, use a higher value resistor..

e.g. if you will use 3.3v, you'd usually pair it with a 330ohm or a 470 ohm resistor..
so if you don't have a 3.3v, you'll want to use a 470 ohm or a 560ohm resistor

covert mortar Jul 19, 2023, 5:08 AM

#

do you think this issue is because of this specific geprc rx as well?

tribal robin Jul 19, 2023, 5:08 AM

#

covert mortar do you think this issue is because of this specific geprc rx as well?

I don't think so..

#

an EP1, and RP1 and the like will behave like that as well..

#

the iFlight receivers could fare better, because afaik, those have on-board pull-ups..
because iFlight knew their FCs have the pull-down issue

covert mortar Jul 19, 2023, 5:13 AM

#

hmm i see. i just don’t get why this is randomly an issue. i’ve been flying this quad for months without a problem

tribal robin Jul 19, 2023, 5:15 AM

#

it always work without issue with the vista disconnected? not a single bootloader mode when vista is disconnected?

covert mortar Jul 19, 2023, 5:17 AM

#

yeah i’ve been flying it for the past 2-3 months consistently. didn’t switch out a single part, was always using the vista

#

never had a problem at all

tribal robin Jul 19, 2023, 5:18 AM

#

I mean have you tried with the vista disconnected whether the receiver will still power up in bootloader mode?

covert mortar Jul 19, 2023, 5:18 AM

#

oh

#

so yesterday, every single time the vista was disconnected, it would work fine

today, when i tried it about 10 times, every time the vista was disconnected, it would work fine. but now, even with the vista disconnected, it stays in bootloader mode

#

but this only started happening maybe the past 2-3 times i tried, just now

tribal robin Jul 19, 2023, 5:20 AM

#

were you power-cycling the receiver as test? how soon were you powering it off then powering it off again? sudden power drops?

covert mortar Jul 19, 2023, 5:21 AM

#

i would power it on, hold it for maybe 2-3 seconds, see that the light isnt blinking, and then disconnect

tribal robin Jul 19, 2023, 5:22 AM

#

do you have another receiver you can swap over?

#

(I'd still recommend the pull-up though)

#

curious why it's behaving this way now though..

covert mortar Jul 19, 2023, 5:24 AM

#

i don’t have a spare one unfortunately

tribal robin Jul 19, 2023, 5:24 AM

#

order one or two..

#

maybe try those from iflight

covert mortar Jul 19, 2023, 5:26 AM

#

would these be okay if i wanted to try a resistor to a 5v pad?

tribal robin Jul 19, 2023, 5:26 AM

#

covert mortar would these be okay if i wanted to try a resistor to a 5v pad?

these might be too big..

#

1/4W pieces should be enough

#

(they are smaller)

covert mortar Jul 19, 2023, 5:27 AM

#

#

470 good enough for 5v? or you recommend going higher to 560?

#

i heard lower is more effective

#

not sure if thats true

tribal robin Jul 19, 2023, 5:27 AM

#

470 ohm should be good

covert mortar Jul 19, 2023, 5:28 AM

#

got it, thanks. ill order some and see if that fixes it

#

are iflight ones the only ones with a built in pull up?

#

i was going to order an ep1 dual or superd eventually

tribal robin Jul 19, 2023, 5:29 AM

#

afaik, iflight are the ones that do..

covert mortar Jul 19, 2023, 5:31 AM

#

got it

#

i assume trying to reflash the rx wont do anything right?

#

i dont know what would suddenly cause it to go into bootloader after a few months of use

tribal robin Jul 19, 2023, 5:32 AM

#

I don't think reflashing would do anything different.. more so it has been working well previously..

covert mortar Jul 19, 2023, 5:37 AM

#

hmm got it

covert mortar Jul 20, 2023, 10:06 PM

#

i just wanted to check something with the pull up resistor. i wire one end to the uart rx pad that i'm using for the receiver (in my case, r5), correct?

and then, the 5v pad that i use, can it be the same one thats powering my receiver? or does it have to be an empty one?

covert mortar Jul 20, 2023, 10:57 PM

#

@old minnow

#

if you have any other suggestions to try, im all open before i try the resistor

old minnow Jul 20, 2023, 10:59 PM

#

Why can't you move the receiver to a different UART?

covert mortar Jul 20, 2023, 10:59 PM

#

covert mortar i just swapped them, same thing

i tried swapping uarts here

#

and the same thing still happened

old minnow Jul 20, 2023, 10:59 PM

#

Rewire your receiver to a non-SBUS UART and show some photos of your wiring

#

It either goes into bootloader or it doesn't. If it works sometimes but not others it sounds like you have a different problem

covert mortar Jul 20, 2023, 11:01 PM

#

my sbus uart is uart 2, my vista is on uart 1. i tried uart 5, didnt work. theres uart 3, but my fc manual says thats for sda/scl for my gps, so thats being used

#

but idont get why uart 2 or 5 wouldnt work

old minnow Jul 20, 2023, 11:01 PM

#

Can you show some clear photos of your wiring?

#

What FC?

covert mortar Jul 20, 2023, 11:02 PM

#

old minnow Can you show some clear photos of your wiring?

i dont have them wired up anymore, i took it apart since the last test i did

#

i can try it again tonight

#

span f722 bt hd v2 (geprc)

old minnow Jul 20, 2023, 11:02 PM

#

Do that, or order a new receiver

covert mortar Jul 20, 2023, 11:02 PM

#

i flew it fine for 2-3 months, without any issues

#

and then one day, it just randomly went into bootloader

old minnow Jul 20, 2023, 11:04 PM

#

For a F7 FC SBUS doesn't matter, there are no pull down resistors

#

This is a hardware problem, either FC or receiver

#

I'd replace the receiver first as that is cheap

covert mortar Jul 20, 2023, 11:06 PM

#

oh. so these won’t work?

old minnow Jul 20, 2023, 11:07 PM

#

They would if it was a pulldown issue, but it isn't

covert mortar Jul 20, 2023, 11:08 PM

#

mm got it

#

how would i tell if its a pulldown issue? if swapping to a different uart fixed the problem?

old minnow Jul 20, 2023, 11:11 PM

#

That's one way, but the pulldown issue is due to hardware inverters used on F4 FCs. They're not used on F7 FCs because they support software inversion. And also it wouldn't work for some time and then stop working, if it was a pulldown issue it would have never worked on that UART without a pullup.

covert mortar Jul 20, 2023, 11:12 PM

#

ah gotcha

tribal robin Jul 21, 2023, 1:31 AM

#

old minnow That's one way, but the pulldown issue is due to hardware inverters used on F4 F...

it was worth a test, imho.. more so it's very abnormal..

#

what was very odd here is that with the vista disconnected, it'll work without issue..
with the vista connected, with with just the vcc and gnd, the issue will rear its head..

old minnow Jul 21, 2023, 1:52 AM

#

tribal robin what was very odd here is that with the vista disconnected, it'll work without i...

It didn't sound like it always worked with the Vista disconnect though... But if is is only when the Vista is powered it sounds like a failing BEC or regulator on the FC

tribal robin Jul 21, 2023, 1:52 AM

#

old minnow It didn't sound like it always worked with the Vista disconnect though... But if...

the last few posts did menioned that the receiver has started acting up..

old minnow Jul 21, 2023, 1:53 AM

#

Could be both FC and receiver 😅

tribal robin Jul 21, 2023, 1:54 AM

#

it could be power rails, yes.. but the vista has been the biggest factor of the issue..

#

could also be the vista pulling way too much, more than necessary..

#

this will be an expensive testing, requiring you to have double of all devices to test.. 😄
might want to just swap flight controller, or ditch the vista and go back analog..
and even that might still not fix the issue, if it's the FC afterall.. or the receiver itself.. 😄

It is weird, since it's not consistent..

covert mortar Jul 24, 2023, 8:56 PM

#

i swapped out the geprc elrs rx to an ep1, and everything seems to be fixed now!

#GEPRC Nano ELRS RX Randomly Bricked (Tentative???)