Late (Dumpster) Santa - found a 2.4GHz controlled car with no chip markings - Page 1
Forum section: electronics / general

author: RoGeorge
author_rank: Super Contributor
timestamp: January 25, 2020, 10:23:16 pm
content: 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!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?

author: MT
author_rank: Super Contributor
timestamp: January 25, 2020, 10:44:07 pm
content: Wet the surface, sometimes sanding is not 100% and shows some text

author: TerraHertz
author_rank: Super Contributor
timestamp: January 28, 2020, 12:09:35 pm
content: 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) RDA58071BPin 4 is Antenna input.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: January 28, 2020, 12:56:23 pm
content: 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.

author: TerraHertz
author_rank: Super Contributor
timestamp: January 28, 2020, 01:44:35 pm
content: Surprisingly, the same car has a second 2.4GHz receiver in the motor control block.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 28, 2020, 06:33:31 pm
content: Quote from: Ed.Kloonk on January 28, 2020, 12:56:23 pmDog and Cat already reported you to the Admins!Quote from: TerraHertz on January 28, 2020, 01:44:35 pmIs 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.Quote from: MT on January 25, 2020, 10:44:07 pmTried water and IPA, but with no luck. From some similar Nikko toy, the Rx chip might be X2455 (because of a similar pinouthttps://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-94140R24Schematic diagram:https://fccid.io/V9Q-94140R24/Schematics/Circuit-Diagram-2989596Internal pics:https://fccid.io/V9Q-94140R24/Internal-Photos/Internal-Photos-2989601All 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 fromhttps://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?