Comma AI self driver assistant

[astrand1]

Why does it need to be 8-9ft long? Maybe I missed something but curious.

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[Ajzride]

Why does it need to be 8-9ft long? Maybe I missed something but curious.

It's an electronics issue having to do with canbus signal reflections on an unterminated stub. You can read the whole techincal discussion here:

https://github.com/commaai/openpilot/issues/30302#issuecomment-2681736903

The summary is we need to add resistors close to the rearview mirror to kill off the reflections. Currently that is done by extending the harness and using only the short USB. But in theory you could use a long USB and a short USB (like they sent you) with some resistors in the coupler. That is what I'm going to try and make this week.

 

[astrand1]

It's an electronics issue having to do with canbus signal reflections on an unterminated stub. You can read the whole techincal discussion here:

https://github.com/commaai/openpilot/issues/30302#issuecomment-2681736903

The summary is we need to add resistors close to the rearview mirror to kill off the reflections. Currently that is done by extending the harness and using only the short USB. But in theory you could use a long USB and a short USB (like they sent you) with some resistors in the coupler. That is what I'm going to try and make this week.

Copy that. Thanks for the TLDR version. keep us updated. I’m definitely in on a group buy if it works.

 

[UncleTony]

It's an electronics issue having to do with canbus signal reflections on an unterminated stub. You can read the whole techincal discussion here:

https://github.com/commaai/openpilot/issues/30302#issuecomment-2681736903

The summary is we need to add resistors close to the rearview mirror to kill off the reflections. Currently that is done by extending the harness and using only the short USB. But in theory you could use a long USB and a short USB (like they sent you) with some resistors in the coupler. That is what I'm going to try and make this week.

Working perfectly. I'll let you take the PCB design on.

 

[Ajzride]

Working perfectly. I'll let you take the PCB design on.

Well, this is exactly what I was going to try. I misunderstood what you had done.
I can skip prototype and go to PCB Design.

 

[UncleTony]

Well, this is exactly what I was going to try. I misunderstood what you had done.
I can skip prototype and go to PCB Design.

I originally mutilated a thunder bolt 3 cable and added resistors as needed. I went to a funeral over the weekend out of state and the boards were in by the time I made it back, just finished this today.

I shortened my jumpers so I can leave it installed and test it out. I was mostly stuck on the pcb design as I'm not an electrical engineer by any means.

 

[Pod]

So….reading the new posts was getting my hopes up. My XLT without adaptive cruise will not work with this, right. Bummed.

 

[Ajzride]

So….reading the new posts was getting my hopes up. My XLT without adaptive cruise will not work with this, right. Bummed.

You can install radar DIY. It's been done by quite a few.

 

[UncleTony]

Just adding this in case anyone wants to get rid of the can bus errors and doesn't already have the custom harness. This is to be done at your own risk as I have only tested it for about 50 miles so far.

You just need these breakouts https://a.co/d/hFHdHoM as well as these resistors (as suggested by @Ajzride) https://a.co/d/h7GIwWR.

All you have to do is bridge B2 to B3 and A10 to A11 with the 62 ohm resistor on the breakout board. I would strongly suggest cutting the wire down as much as you can and solder the resistor into the wire. I would also not suggest you use this as a long term solution, but could save you from spending more or modifying your existing harness while the PCB gets worked out.

Everything you need outside of the resistors and what you need to solder is included in the kit.

Edit to add what mine looks like when complete now that I've had the time to solder it properly.

 

[B177y]

So….reading the new posts was getting my hopes up. My XLT without adaptive cruise will not work with this, right. Bummed.

I added ACC/LKA to my 2024 Pro following this thread. It was worth the hassle.

I ordered a Comma and I'll post here if it works.

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