CAN bus or LIN Bus

pete_d

pete_d

New Member
Hi everyone,

I'm planning to monitor the status of my doors (locked/unlocked) and windows (open/closed) in my T6 when the car is turned off. My idea is to use an ESP32 microcontroller along with a CANbus or LINbus transceiver. However, I'm not sure if these specific messages are transmitted via the CAN or LIN bus, or possibly both.

Could anyone share recommendations on the best points to tap into these bus systems? Additionally, if anyone has alternative suggestions for monitoring door and window status, I'd be very interested.

Recently, one of our cars was left unlocked overnight, and unfortunately, items were stolen. This car has connected services, so we set up a 3D printed model car on our TV. It glows red if the car is left unlocked. Since the van is always within our home's Wi-Fi range, I'm trying to create a similar device for it. Any guidance or advice from the community would be greatly appreciated!
 
Not much is done over linbus (rain sensor and alternator are a couple that spring to mind) the info you need would be communicated on the canbus network, the convenience canbus to be specific as there’s also a drivetrain canbus for engine/gearbox signals etc
The canbus wiring runs throughout the dash area so it’s easy enough to access and tap into but no idea on capturing and transmitting it I’m afraid
 
Thanks, Pauly. It looks like I'll be focusing on the CAN bus, which rules out the LIN bus for this project.

Capturing the data is relatively straightforward for me, but the main challenge lies in finding a suitable physical connection point. I'm looking for a convenient way to access the CAN bus cables without having to dismantle the entire dashboard. There are suggestions that the cables run through the driver's door, but it seems not many have had success with this approach.

Accessing through the OBD port is an option, but it requires transmitting messages to request status. I’d prefer to create a read-only device to avoid any potential issues caused by incorrectly formatted messages.

I'd really appreciate any suggestions on where to tap into the CAN bus cables.
 
Either directly from the BCM under the dash but it’s fiddly to get at or, at the back of the head unit in the quadloc connector.
 
folding mirrors are LIN Bus too
 
Central locking goes just directly to BCM and therefore the status either has to be read from wires directly or extracted from CAN data. Window statuses on the other hand are transmitted by the door control modules in the doors via LIN first to BCM but then translated on to CAN messages. So, to get both the lock and window statuses from a single location it makes sense to look at CAN directly.

As mentioned earlier in the thread, the convenience CAN is the correct bus for this and easiest reached behind the radio or aircon control unit (at least in climatic / climatronic).

For decoding locks: code_composer_build/MOD/MOD_CAN_DYN/cfg/PQ35_46_ICAN_V3_6_9_F_20081104_ASR_V1_2.dbc at a34f54cdee679d0b1104b527aafde5f17054634c · speedbyte/code_composer_build

For decoding windows: code_composer_build/MOD/MOD_CAN_DYN/cfg/PQ35_46_ICAN_V3_6_9_F_20081104_ASR_V1_2.dbc at a34f54cdee679d0b1104b527aafde5f17054634c · speedbyte/code_composer_build

Not entirely sure if above messages are transmitted by your van and if they are also available in sleep states - convenience CAN goes to partial shutdown when parked.
 
I was about to mention you might want to read some of the threads by @n10n who does near continuous CAN bus data capture, but I note you attracted thier attention anyway :thumbsup:
 
n10n said:
Central locking goes just directly to BCM and therefore the status either has to be read from wires directly or extracted from CAN data. Window statuses on the other hand are transmitted by the door control modules in the doors via LIN first to BCM but then translated on to CAN messages. So, to get both the lock and window statuses from a single location it makes sense to look at CAN directly.

As mentioned earlier in the thread, the convenience CAN is the correct bus for this and easiest reached behind the radio or aircon control unit (at least in climatic / climatronic).

For decoding locks: code_composer_build/MOD/MOD_CAN_DYN/cfg/PQ35_46_ICAN_V3_6_9_F_20081104_ASR_V1_2.dbc at a34f54cdee679d0b1104b527aafde5f17054634c · speedbyte/code_composer_build

For decoding windows: code_composer_build/MOD/MOD_CAN_DYN/cfg/PQ35_46_ICAN_V3_6_9_F_20081104_ASR_V1_2.dbc at a34f54cdee679d0b1104b527aafde5f17054634c · speedbyte/code_composer_build

Not entirely sure if above messages are transmitted by your van and if they are also available in sleep states - convenience CAN goes to partial shutdown when parked.
Click to expand...
Thanks for this, It should save some time! I was going to write a basic sketch that listens to all the raw data and then try to work out what messages i need to look at by lost of testing, this should save a lot of time.
 
@pete_d Good luck and please do share how your project progresses (or doesn’t). And yes, VIP membership recommended! :whistle:
 
pete_d said:
Hi everyone,

I'm planning to monitor the status of my doors (locked/unlocked) and windows (open/closed) in my T6 when the car is turned off. My idea is to use an ESP32 microcontroller along with a CANbus or LINbus transceiver. However, I'm not sure if these specific messages are transmitted via the CAN or LIN bus, or possibly both.

Could anyone share recommendations on the best points to tap into these bus systems? Additionally, if anyone has alternative suggestions for monitoring door and window status, I'd be very interested.

Recently, one of our cars was left unlocked overnight, and unfortunately, items were stolen. This car has connected services, so we set up a 3D printed model car on our TV. It glows red if the car is left unlocked. Since the van is always within our home's Wi-Fi range, I'm trying to create a similar device for it. Any guidance or advice from the community would be greatly appreciated!
Click to expand...
All statuses are in CAN. But the problem is that after some time the car falls asleep and data is not transmitted to the CAN
 
The door modules communicate with the BCM by LIN. I think you know that the lin consists of a Master and a Slave, so in normal mode you can just listen to the LIN, and when the car has fallen asleep, you can pretend to be the Master and interrogate the door module
 
F-roger said:
All statuses are in CAN. But the problem is that after some time the car falls asleep and data is not transmitted to the CAN
Click to expand...
I think it will still be ok. Unlocking for sure wakes the CAN and you can’t open/close windows anyway while the van is taking a nap.

So… OP should make ESP32 remember last CAN state when no new messages arrive. Still, ESP32 should transmit something periodically even though van is sleeping just so that communication dying (or van nicked, hope not) is also visually apparent
 
Hi all thanks for keep posting. I assume when a event happens the can is updated even if it is sleeping.

The ESP will remember last state and only update the 'server' via wifi when it see a Message it cares about.

So hopefully it going to sleep should not be too much of an Issue.
 
Last edited:
pete_d said:
Hi all thanks for keep posting. I assume when a event happens the can is updated even if it is sleeping.

The ESP will remember last state and only update the 'server' via wifi when it see a Message it cares about.

So hopefully it going to sleep should not be too much of an Issue.
Click to expand...
I know for sure that when disarmed, CAN wakes up, I don't know if this happens in case of an alarming event!

If you use the LIN, you will have access to the control of the central lock and power windows.
 
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