LIN bus interception

Ideas and discussion of what to do with the CAN Bus ( i.e. XMDirect, iPod, Carputer, etc... )
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nr0x
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Joined: 2014 Jun 19 08:55

LIN bus interception

Post by nr0x » 2014 Jul 22 01:57

Ok, I had another hair brained off the wall idea.

So I monitor the interior bus, and I see traffic. I identify the message that turns the lights on. I send that message. The lights turn on, and then immediately go back off. That is because the module that normally sends that message is saying "this is MY bus, bi*ch". The OFF signal is being constantly sent, because that is what position the switch is in, so even when you DO send a message, it gets counteract right away.

So what we need is a big red "Shut The Frick Up" button. I'm a picaxe kid, so naturally I wonder if I can get a chip to help out. Here is my thought.

What if you take the lin bus off the instrument cluster (I think that is where it gets to the interior bus through) and stuck a picaxe in there instead. Then the picaxe could listen to bus traffic, and forward it all to the instrument cluster, which would be none the wiser.

But then you could tell it to block certain messages. Now when I turn the lights ON by command, the chip stops forwarding the OFF command to the cluster, and the lights stay on.

Being able to intercept, block, and filter the lin bus like this could make for some pretty cool stuff. I don't use that hands-free button on the steering wheel ever, so what if I made it a multifunction button? Tapping the left signal lever makes the left signal blink 3 times. Tap the hands free button THEN the signal, and you turn on your left side floodlights instead. Tap it before hitting the hazard light switch, and you turn on the safety strobes. And of course, the same microcontroller can send 295 commands to the cluster, and use the EVIC to tell you what you just turned on.

I mean, if I can wrap my head around this, it could attend multipurpose function to anything on the linbus. And I'm one of those guys who hates drilling up the dash to mount switches, so this is pretty badass to me.
Granted that there is a big difference between a crazy idea and something that works, but this is definately going on my "watch this sh@t" list.

Anybody got any thoughts?

OBDRipper
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Re: LIN bus interception

Post by OBDRipper » 2014 Jul 22 06:53

Nice idea, only problem is the cluster has many functions, so it means you will have to thoroughly know how it works otherwise you might end up loosing a feature or 4.
Ive done it before, switch on head lights , but then it just goes off straight away, I then flood it, and it stays on but every now and again it dips and comes back on again.
Not a lekke solution though, bit dodgy.

In stead find a digital button that doesnt have an on or off position, I.E in my Case my Jeep Rubicon has a swaybar disconnect button, which only send the message 1 once when you press it once.
1 press for on and another press for off.

Here is an example of what i have done.
https://www.youtube.com/watch?v=cAHTUXI8yVY
i made a device that hooks up to the CAN-BUS then switches on the swaybar light by pressing once.,


You can then change it if you press the button 5 times in say 10 seconds it switches something else on and if you press it 5 times again, it switches it off again (I'm thinking external 3rd part accessories like an LED light bar)
and if you haven't pressed the button in 10seconds it resets it 5 time counter. (The sway bar will not disconnection when in high range instead the light will just flicker)

nr0x
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Posts: 22
Joined: 2014 Jun 19 08:55

Re: LIN bus interception

Post by nr0x » 2014 Aug 11 21:02

I see what you're saying. Hopefully, if this works, it will stop them from turning right back off. I've tired flooding, too. Crappy at best. My goal here is to kind of make everything on the linbus act just like your switch does.
Now does anyone happen to know the linbus speed and protocol for a 2014 Jeep JK? I had it written down somewhere, but I can't find out now.

nr0x
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Posts: 22
Joined: 2014 Jun 19 08:55

Re: LIN bus interception

Post by nr0x » 2015 Jan 27 12:55

Yea, I haven't done much here yet. Paycheck and sanity come before hacking. But now that winter is settling in, I've found myself with more desk time, and Im trying to get back to work on this idea. I'll try to keep in touch.

robertoal
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Re: LIN bus interception

Post by robertoal » 2016 Mar 02 10:33

I have the exact same problem, only i want to make double use of the radio control panel: Mode 1 for integrated car audio, mode 2 for controlling my tablet.

What I had in mind, although i have no clue if it would be possible, is using an arduino.
Theoretically you could use the arduino to just bridge te messages: Digital I/o IN (from your light switch) -> to Digital I/O out (to canbus network from the vehicle)
Then when you want to control a function you program the arduino that by repeating message X it will go into 'custom' mode: so only messages you want will be sent.
All this just with using raw data, so without the intervention of an interpreter like the ELM327.

Some of the potential problems i can think off:
- Latency - although this probably only will be a problem with High speed busses
- Number of messages from the slave node - Putting an arduino between the ECU and the car wouldn't be a great idea
- Only possible with non critical secondary node's
- If an ELM327 (or the like) chip HAS to be used: cost
- When the arduino isn't working well: possibility of flooding the network?

Pro's:
- Unlimited functions per key/function button
- Without an ELM -> quite cheap to implement
- Just plain cool :)

Would love to know your thoughts! And if you guys thinks this would be even remotely possible :-)

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