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General => General Technical Chat => Topic started by: cybermaus on November 24, 2024, 07:37:13 am

Title: Canbus box CanBox Rx/Tx voltage levels
Post by: cybermaus on November 24, 2024, 07:37:13 am

Hello. Small question.
Hello

I recently build a CanBox decoder model  RP5-RN-101 into my Renault Traffic III, and the aftermarket android car radio is not seeing the signals.
Measuring, I see Tx/Tx have 0,35V
That seems very weak. (see image)

For normal TTL based serial, this is *way* too low, but I know lttle of these units, maybe this is current driven levels, not voltage drive. (Note: I am talking about Rx/Tx between Box and Radio, not about CAN-H and CAN-L)


(BTW: it shows the same 0.35V with, and without plugging Rx/Tx in, so that would hint it is not current driven, as voltages would rise without a drain.)
See image

Can anyone confirm what the correct voltage levels should be on typical china CAN boxes? Indeed 0,35V, or a more normal 3.3V or even 5V

Ref: CanBox RP5-RN-101 Renault

Title: Re: Canbus box CanBox Rx/Tx voltage levels
Post by: darkspr1te on November 24, 2024, 08:18:54 am

The CANBOX units for android radio's usually have the following pinouts


20 pin adapter

Code: [Select]

1: Batt                                       2: GND
3: AVC -                                     4: AVC LAN +
5: REVERSE OUT To HeadUnit   6: ILL-OUT to HeadtUnit
7: REV CAM Power                    8: Park Signal IN
9: IGN In                                   10: ACC in
11: CAN-L to Car                      12: CAN-H to Car
13: NC (model feature)            14: H/Unit RX Can data (3.3v)
15: H/Unit TX Can data (3.3v)  16:NC (model Feature)
17:Amp In Signal                     18: SWC1
19: SWC2                                 20: SWC3

In this case the unit I have posted is a Toyota/Lexus unit.
H/Unit TX/RX is a uart type signal for comms from canbox to the mcu on the Android head unit (MCT/MCD/FTY etc) which in turn tell android whats going on with the various BUS's this lexus would have.

AVC LAN is the car's audio system comms control for vehicles. (bmw has it's own system so does merc )
SWC1/2/3 is a resistor based switch that reads teh Steering wheel control. (this is very common for 2000+ year vehicles as it's super simple to read many buttons from just 2/3 wires.

I have *LOT* of documentation posted on xda forums on this subject already, you should search darkspr1te + canbox on xda.
as well as code samples on my github

attached also is the 16 pin v/w and volvo shcematics.


darkspr1te

Title: Re: Canbus box CanBox Rx/Tx voltage levels
Post by: darkspr1te on November 24, 2024, 08:27:06 am

You should also state what android model/device  you have as there are many diff systems (MTCD/FTY etc) and they use different menus to access the canbus settings where  you set it if it's a Simplesoft unit, RCZ, Raise and other brands. that does normally need to configured but i have a noticed a new trend on some brands to have a auto detect but that does not always work.




darkspr1te

Title: Re: Canbus box CanBox Rx/Tx voltage levels
Post by: cybermaus on November 24, 2024, 09:35:08 am

Quote from: darkspr1te on November 24, 2024, 08:18:54 am

The CANBOX units for android radio's usually have the following pinouts

Thanks, I will search and read for your stuff. HOWEVER I have to urge you to be cautious on showing your "default pinout" to strangers with unknown boxes
While a noob, I found SEVERAL incompatible pinouts, none of them mine, but after research I can *definitely* state that my RP5-RN-101 pinout is as below in th eTraffoc III column

Anyway, you confirm UART level, so 0.3 V is just too low, right?

Title: Re: Canbus box CanBox Rx/Tx voltage levels
Post by: darkspr1te on November 24, 2024, 10:50:35 am

The TX signal from the CANBOX is pulled high by the RX(radio) and pulls canbox pulls RX low to transmit so you wont see a voltage on TX when not connected to RX on the radio. you should see 3.3v on RX but nothing on tx when not connected, and same on the radio. (it often gets confusing remembering a device RX/TX High/low levels ) 


Yes I know there not default pinout, it it's up the the reader really to interpret the info to apply to themselves. hence the mention that Toyota have AVLAN but BMW has EBUS and merc has KLINE , while the physical interface of these 3 bus'es is the same (rs485) electrical interface they all 3 work on differing protocols. There is also the was you read the pin out, eg top down/left right or left right /top bottom 


Also i have posted about 10 different pinouts & schematics on the XDA threads with the most common pins marked to support as many in my code and to get feed back but rarely happens, the second problem is the two alternate types of radios these unit mate too but that another discussion.


Be aware there is a known thing on citreon/renualt that boxes are ment for pre 2017 vehicles or post-2017 , theres a thread on xda covering this in a megane(2012) and a little toyota (2018) , quite detailed too.




darkspr1te

Title: Re: Canbus box CanBox Rx/Tx voltage levels
Post by: cybermaus on November 24, 2024, 06:27:05 pm

Turned out there is a menu hidden behind a pascode, in my case 8888, where you have to select model box and model car.

I simply select "basic" brand box rather then a specific brand. Renault Capture by lack of option for Renault Traffic III, and it works.

Mort importantly: volume and phone.
Less important, but also working: AC info, door open/ajar info.

I think without select any canbus, it is simply not driving the lines high, so the canbus is not able to sinc it low, therefore the very meager signal.
Thanks @darkspr1te