JB4 & Comma Two (fighting for OBD II)

[stonger]

Hi there,

I've got a first world problem here with a 2018 GT2 AWD - I'm trying to have a self driving car, and a fast car, but I don't think I can have both at the same time.

I'm running a Comma Two (see comma dot ai for their website, can't post a link) for self driving on long trips, which is brilliant, but I also want to run the JB4 for ripping around. The Comma Two requires the OBD port to take over the steering. If anyone wants a write up on what this is like, let me know and I'll make another thread.

My questions are

1. Given the OBD II port is a serial port, rather than a bus, there's zero chance of running both devices at the same time, correct?
2. How much is performance of the JB4 affected by not running the OBD port? Can I run map 0/1/2 without the OBD plugged in?
3. Am I able to plug/unplug the OBD for the JB4 while the engine is running? i.e. after a highway trip can I unplug the Comma, and plug in the JB4 without stopping the engine?
4. I assume the JB4 is using the OBD for closed loop control on more aggressive maps. Is there a map that is safe/reliable to run without feedback. I know other stock ECU solutions like APR tunes don't require OBD but they're running on the ECU rather than piggy backing.

Cheers,

Stonger.

 

[Luc343]

The link is comma.ai – Introducing openpilot

Wow, that's very interesting...

 

[Intelliburn]

Hi there,

I've got a first world problem here with a 2018 GT2 AWD - I'm trying to have a self driving car, and a fast car, but I don't think I can have both at the same time.

I'm running a Comma Two (see comma dot ai for their website, can't post a link) for self driving on long trips, which is brilliant, but I also want to run the JB4 for ripping around. The Comma Two requires the OBD port to take over the steering. If anyone wants a write up on what this is like, let me know and I'll make another thread.

My questions are

1. Given the OBD II port is a serial port, rather than a bus, there's zero chance of running both devices at the same time, correct?
2. How much is performance of the JB4 affected by not running the OBD port? Can I run map 0/1/2 without the OBD plugged in?
3. Am I able to plug/unplug the OBD for the JB4 while the engine is running? i.e. after a highway trip can I unplug the Comma, and plug in the JB4 without stopping the engine?
4. I assume the JB4 is using the OBD for closed loop control on more aggressive maps. Is there a map that is safe/reliable to run without feedback. I know other stock ECU solutions like APR tunes don't require OBD but they're running on the ECU rather than piggy backing.

Cheers,

 

[Intelliburn]

It would be nice if there was a OBDII splitter

 

[stonger]

It would be nice if there was a OBDII splitter

There is, but they're sketchy.

The issue is (based on my understanding) it's a serial port, not a bus (like CAN bus, or Universal Serial Bus - USB).

It's been a while since I've done low level stuff with a serial port, but without digging into how the comma communicates with the car (luckily it's all open source) I don't really want to risk steering input packets from the comma getting stomped on by the JB4 while I'm doing 75mph around a corner without my hands on the wheel. Similarly, I don't want the OBD-II output (JB4 input) getting corrupted and getting spurious engine management output from the JB4.

Secondly, looking at the various OBD-II specs (haven't looked what variant the Stinger implements) their bandwidth is crap - like 10.4kbps crap. It's a known limitation with data logging having pretty poor resolution and it's why you do pulls for road tunes in 3rd/4th, so you can get enough resolution on time/RPM.

Even if I can run both at the same time from a physical and electronic perspective, there may not be enough overhead in the protocol to support both communicating at the same time, so I figured I'd ask the experts

 

[Avon]

You don't need the obd-II for the comma it is powered and fully controlled via the harness you bought with the Comma 2. I have one on my car now right now. @stonger

 

[stonger]

The link is (see link from OP above - I'm not allowed to post links)

Wow, that's very interesting...

Yeah, for $1200 it's wildly good value, and wouldn't hesitate to recommend to anyone.

It's not perfect, and I'm not about to jump in the back seat like a 16 year old TikTok kid in a Tesla, but it's pretty f*cking good.

If you can see the lane lines, and the curves aren't outrageous (on/off ramps/winding mountain passes), it's about as good as Tesla's autopilot at lane centering, and it won't jerk you into concrete barriers at full speed like a Tesla can.

It can even change lanes with assistance. Put your indicator on, check your blinds spots (it can only see forward), and nudge the wheel, and it'll change lanes.

For anyone playing along at home, I've done the I-70 mountain drive a few times with it. In 200 miles I only had to assist it around 3 bends that were too sharp (45mph suggested corners while cruising at 65mph) and it drifted out of a lane once, because the lane line was rutted away and simply didn't exist.

None of it catches you by surprise - you quickly learn the limitations and learn where you can completely trust it, and where it might need a bit of baby sitting. You can help it around corners by steering and it won't disengage, or adjust your position in a lane based on a truck/shitty driver nearby.

Under 99% of circumstances it's extremely reliable and a major upgrade over the SCC and LKAS (the stock system is next to useless IMO).

It's amazing to be able to look out the windows at scenery on long straight sections with little traffic, and an absolute god send in long traffic jams. It can slow to and start from 0mph while engaged and will follow the lane you're in till you run out of gas.

 

[stonger]

You don't need the obd-II for the comma it is powered and fully controlled via the harness you bought with the Comma 2. I have one on my car now right now. @stonger

Oh dude, seriously? I need to go for a drive now to check this.

What's the OBD-II for then? I assumed it was communicating over OBD. It must be injecting into the stock LKAS and giving it more accurate estimation of the lane position.

 

[Avon]

@stonger IDK for sure but been told by people on discord that know more about it than me that it wasn't needed and sure enough isn't. Maybe it is because on some platforms it is needed so they just include it. Again IDK. BTW what branch you using? My tune is good but has a pesky minor bounce in straight aways at highway speed.. Thanks.

 

[stonger]

@stonger IDK for sure but been told by people on discord that know more about it than me that it wasn't needed and sure enough isn't. Maybe it is because on some platforms it is needed so they just include it. Again IDK. BTW what branch you using? My tune is good but has a pesky minor bounce in straight aways at highway speed.. Thanks.

I'm using the standard release branch from comma. I haven't looked into forks extensively yet.

Have you got a shortlist of forks that you could recommend? I know what you mean about the wiggle it does.

Once they get longitudinal control working I'll take a look. I'm in the discord but haven't really dug into things yet.

 

[Avon]

I actually haven't tried an official branch in over a year now. A buddy on mine has a branch that I use. I better ask him before I post about it. Liability and all. Maybe I should just try an official branch myself as it has been along time.

 

[Terry@BMS]

It's not going to work right and we have zero interest in hearing about how you tried to get both working and self drove your car off a cliff.

Just use JB4 without OBDII if that is what you want to do. You'll make less power but it's still way better than factory.

 

[stonger]

It's not going to work right and we have zero interesting in hearing about how you tried to get both working and self drove your car off a cliff.

Just use JB4 without OBDII if that is what you want to do. You'll make less power but it's still way better than factory.

Given what @Avon said I'll confirm the comma works without OBD-II and if that's the case I'll run the JB4 with OBD and the comma without.

Don't worry - you probably won't hear from me if I go flying down a ravine

 

[stonger]

I actually haven't tried an official branch in over a year now. A buddy on mine has a branch that I use. I better ask him before I post about it. Liability and all. Maybe I should just try an official branch myself as it has been along time.

Not concerned about the liability - it's open source and I take full responsibility for driving. Their safety model is solid.

 

[Einate]

Not concerned about the liability - it's open source and I take full responsibility for driving. Their safety model is solid.

Hey man, I'm getting ready to do exactly this. Did you ever get both to work?

 

[Einate]

Not concerned about the liability - it's open source and I take full responsibility for driving. Their safety model is solid.

Hey man, I'm getting ready to do exactly this. Did you ever get both to work?

 

[jzc0125]

Any updates? Got the jb4 installed and about to purchase the comma 3