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Topic: BPv3.6 Getting Started - how do I identify the signal in a RC car controller? (Read 143 times) previous topic - next topic

BPv3.6 Getting Started - how do I identify the signal in a RC car controller?

Working on a project to programmatically inject commands to an RC car controller; I've opened it up (photos linked below):
https://photos.app.goo.gl/iiEfXgRKhvKzsiKk8

I think the most straightforward way is to tap into the signal wires coming off of the left/right and accelerator controls.  On the image they are the two sets red/yellow/black wires coming into connectors off the top of the PCB.

I measured the red/black voltage at 3V.  How would I use the BP to identify the signals on the yellow wires?

Re: BPv3.6 Getting Started - how do I identify the signal in a RC car controller?

Reply #1
Are you trying to control the motors and servos directly, or emulate the RF commands going to the control chip?
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Re: BPv3.6 Getting Started - how do I identify the signal in a RC car controller?

Reply #2
Initially I'm trying to tap into the signals on the controller, figure out how they work/protocols, then put in a chip like an esp32 to be able to programmatically emulate the signals coming from left/right/accelerator.  The controls might just be pots, so I'd just need to generate an analog signal.  But it could be some digital protocol.  How would I hook up the BP to analyze the signal off the controller knobs?  GND and 3.3V I think; which BP pin connects to the signal wire - would that be MOSI or ADC?

What software do you recommend? Someone recommended sigrok but I got the error below and elsewhere I read that it doesn't work with BP:
Code: [Select]
C:\Program Files (x86)\sigrok\sigrok-cli>sigrok-cli.exe --scan
sr: ftdi-la: Failed to get the FTDI strings: -4

So now I'm trying Open Bench Logic Sniffer

Eventually I'll put a chip on the car itself to control it, maybe by emulating the commands between the RF receiver and the motors but for now, controlling it through the transmitter so I can do development from a laptop.



Re: BPv3.6 Getting Started - how do I identify the signal in a RC car controller?

Reply #3
I imagine all the buttons are analog signals. You can hook up the ADC probe to the wires and use the 'D' command in the bus pirate to measure voltage continuously while you press the buttons. You could also use a multimeter though :) Unless you find a digital bus I worry there might not be must the Bus Pirate can do. The logic analyzer will also only measure digital signals, so if it is all analog (I suspect it is) the results won't really be helpful.
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Re: BPv3.6 Getting Started - how do I identify the signal in a RC car controller?

Reply #4
Yes we were thinking the physical controls were just pots, but when I measure the voltage and turn the wheel to the extremes the measured voltage stays at 1.34V; so I'm thinking it may be digital, some kind of rotary encoder.  So I'll try some logic analyzer software that works with BP to see if I can detect any signal coming through.  But I've never done this before so kind of flying blind.