Author Topic: Late (Dumpster) Santa - found a 2.4GHz controlled car with no chip markings  (Read 322 times)

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Online RoGeorge

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Went to the dumpster to throw away some garbage, found a 2.4 GHz remote controlled car near the dumpster, thank you late Santa!

I would have killed for suck a toy when I was a kid!   :D

Looks like a nice platform for future robotic projects, has two brushed motor, one for each each of the left/right sides.  The front/back wheels on the same left/right side are mechanically connected (like in a tank track, just that there is no track between the front and the back wheels).

The RF chip has no markings on it, any clues what can it be, please, or how can I control such a car?
« Last Edit: January 28, 2020, 05:46:30 pm by RoGeorge »
 

Offline MT

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Wet the surface, sometimes sanding is not 100% and shows some text
 

Offline TerraHertz

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Funny coincidence. Today I grabbed a kerb-tossed kid's play electric car. Once upon a time it was switchable between remote controlled and manually (kid) driven. Now it's missing the battery and remote controller, and is so battered and broken it was only worth pulling apart for curiosity.

But, the 'radio' board chip has intact markings. It's a 2.4GHz receiver. See pics.
2nd-last pic is the radio board. Antenna pin circled in red.  RF chip center-bottom. Chip at top left is something to do with audio.
The RF chip number is (I think) RDA58071B
Pin 4 is Antenna input.
« Last Edit: January 28, 2020, 12:15:44 pm by TerraHertz »
Collecting old scopes, logic analyzers, and unfinished projects. http://everist.org
 

Offline Ed.Kloonk

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As a kid, I was never allowed a remote controlled car or such toys because apparently there was a risk that I would torment the dog with it.

A few years ago I saw one for sale in a shop and impulse buy, I brought it home. You'll be pleased to know that not only did I harass the dog, I gave the bloody cat what for as well.

 :)
 
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Offline TerraHertz

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Surprisingly, the same car has a second 2.4GHz receiver in the motor control block.
Collecting old scopes, logic analyzers, and unfinished projects. http://everist.org
 

Online RoGeorge

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As a kid, I was never allowed a remote controlled car or such toys because apparently there was a risk that I would torment the dog with it.

A few years ago I saw one for sale in a shop and impulse buy, I brought it home. You'll be pleased to know that not only did I harass the dog, I gave the bloody cat what for as well.

 :)
Dog and Cat already reported you to the Admins!   ;D

Surprisingly, the same car has a second 2.4GHz receiver in the motor control block.
Is that a nrf24l01 module in the last pic?  If so, you could spy on its pins to find the channel, maybe get some hints about the protocol, too.

About my 2.4GHz Rx side only, I couldn't find yet any documentation about the protocol.

Wet the surface, sometimes sanding is not 100% and shows some text
Tried water and IPA, but with no luck.  From some similar Nikko toy, the Rx chip might be X2455 (because of a similar pinout https://hackspace.raspberrypi.org/articles/can-we-hack-a-radio-controlled-car ) , but I couldn't find any datasheet for X2455 either.

However, the one I found is kind of famous, from NIKKO, named "VaporizR 2" and is for either land or water.  That explains why everything was encased and water sealed, including the batteries and the on/off switch.  They even made video ads about it:


So far I could only find the schematic and the user manual, starting from the FCC ID label:  "V9Q-94140R24".  The FCC ID have a lot of nice PDFs, including pics and RF test.
All docs:  https://fccid.io/V9Q-94140R24
Schematic diagram:  https://fccid.io/V9Q-94140R24/Schematics/Circuit-Diagram-2989596
Internal pics:  https://fccid.io/V9Q-94140R24/Internal-Photos/Internal-Photos-2989601

All clues from other searches indicate NIKKO is using their own protocol for 2.4GHz, and so far I couldn't find any documentation about it (other than the one from the FCC ID site).

I am not very sure what are the R&S spectrum analyzer screenshots at page 10 and 11 from https://fccid.io/V9Q-94140R24/Test-Report/Test-Report-2989597
- Did the receiver actively Tx (for example for pairing with a transmitter remote) or those screens are just for unintended RF radiation coming from the receiver?
- Are those at page 10 and 11 time domain screenshots, or frequency domain?
« Last Edit: January 28, 2020, 06:39:47 pm by RoGeorge »
 


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