Comma AI self driver assistant

[Ajzride]

I went through deciphering how the extension cable works just this afternoon. As I understand it the black Comma junction (Panda?) box would go down near the OBD-II plug (below the A-pillar) and the extension cable you're building would run from there up to the rearview mirror, connecting to the Q4 harness. You would need to also run their long 9.5' USB-C cable from the black junction box up to the 3X.

Does that sound correct?

View attachment 95599

Not quite. Give me an hour.

 

[Ajzride]

going to extend the harness myself, have the alex guide (but the newer harness so no need to cut the initial wires and loop back, just planning on extending all wires and putting resistors on the canbus wires....orange, green, blue and pink).....I have the following that I am going to buy:


one other issue that I thought of, with the new v2 connector the plug from the odb2 to the panda box is no longer connected with an ethernet cable.....it has a small plug...if I extend the wiring so that the box is up behind the mirror then I don't think it will reach.....I could extend it or I guess go without it (supposedly you don't need the odbII connector)

do I have that right?

where did your parts list go?

 

[JerseyMike]

where did your parts list go?

I removed it because I figured it out

where did your parts list go?

I removed because I figured it out watching one of your how to videos also switched around slightly

Solder seal
https://a.co/d/bOMuAwO

Resistors
https://a.co/d/gtFRyrI

femaLe to female
https://a.co/d/bgyX29Q

 

[Ajzride]

I went through deciphering how the extension cable works just this afternoon. As I understand it the black Comma junction (Panda?) box would go down near the OBD-II plug (below the A-pillar) and the extension cable you're building would run from there up to the rearview mirror, connecting to the Q4 harness. You would need to also run their long 9.5' USB-C cable from the black junction box up to the 3X.

Does that sound correct?

View attachment 95599

I guess this is a good time to give a lot of background information, some of which you may already know but could be good for others in the future, to help everyone understand how this works and what the problem is.


The way Comma and OpenPilot work is by intercepting the Canbus communications between the Image Processing Module (IPMA) and the Power Steering Control Module (PSCM). The communications from the IPMA are blocked, and the Comma pretends to be the IPMA and sends its own signals to the PSCM. This is what we call a man-in-the-middle attack in cybersecurity circles. To accomplish this. The comma has to physically break the Canbus network in a place that Comma is certain it can block those communications between the two modules. The only two places this is certain are at the inlet of the PSCM (which is usually under the hood near the steering rack) or at the output of the IPMA. Prior to hands-free driving platforms (BlueCruise, SuperCruise, FSD), the IPMA was almost exclusively located under the rear-view mirror cover. Since the Comma needs to be mounted very close to the rearview mirror to see the road and watch the driver, this made intercepting the Canbus networks at the IPMA the ideal scenario.

This means that 90% of cars that comma works with (including Fords that use the older lane centering technology like Maverick, Explorer, Escape) have a harness that intercepts the Canbus near the rearview mirror, and then a short (18") USB-C cable from the harness to the device mounted right below the IPMA on the windshield. This is a good time to note that the Comma does not actually communicate USB; it is only borrowing a USB cable because of the nice convenient form factor to act as an extension cable for the Canbus networks (this is why the cable specification for Comma is so strict, USB3.2gen2 cables only. lower spec cables don't have all of the pins terminated). To get power to the Comma on the windshield, they ran a long cat5 cable (which has recently been replaced by a 4-pin cable) from the ODB port under the dash to the rearview mirror mounted harness.

When Ford introduced BlueCruise the new IPMA was much more powerful and too large to fit under the rearview mirror cover. For the F150/Lightning/Expedition, it was moved under the dash near the driver's foot, and for the MachE it was placed in the trunk. Comma was of no mind to redesign their whole philosophy to accommodate this change, so they just said, "Use a long USB cable and a short CAT5 cable". This philosophy worked out fine for the F150 and the MachE, but when the Lightning guys started installing a Comma, they ran into issues with the Canbus network that generated the annoying errors.

The heart of the issue is that the long USB-C cable creates a 10-foot-long unterminated stub on the Canbus network, and when the Lightning cranks up it sends out a blast of electromagnetic frequency (EMF) that causes the Canbus communications to be corrupted briefly. To remedy the issue, the extension harness is built, which moves the black box up to the rearview mirror, where it was planned to be based on Comma's initial designs. The two resistors are added across CANBUS-1 positive/negative and CANBUS-2 positive/negative so that the long Canbus wires are no longer unterminated. These resistors prevent the EMF blast from corrupting the communications.

When the harness is completed, the black box moves up to the rearview mirror so you now need a short USB-C, and a long power wire (the 4 pin connector). Technically, you can get by without installing the ODB adapter and the power cable, it just means that the comma will power off between drives and it will take 2-3 minutes to boot up once you start driving.

 

[JerseyMike]

I guess this is a good time to give a lot of background information, some of which you may already know but could be good for others in the future, to help everyone understand how this works and what the problem is.


The way Comma and OpenPilot work is by intercepting the Canbus communications between the Image Processing Module (IPMA) and the Power Steering Control Module (PSCM). The communications from the IPMA are blocked, and the Comma pretends to be the IPMA and sends its own signals to the PSCM. This is what we call a man-in-the-middle attack in cybersecurity circles. To accomplish this. The comma has to physically break the Canbus network in a place that Comma is certain it can block those communications between the two modules. The only two places this is certain are at the inlet of the PSCM (which is usually under the hood near the steering rack) or at the output of the IPMA. Prior to hands-free driving platforms (BlueCruise, SuperCruise, FSD), the IPMA was almost exclusively located under the rear-view mirror cover. Since the Comma needs to be mounted very close to the rearview mirror to see the road and watch the driver, this made intercepting the Canbus networks at the IPMA the ideal scenario.

This means that 90% of cars that comma works with (including Fords that use the older lane centering technology like Maverick, Explorer, Escape) have a harness that intercepts the Canbus near the rearview mirror, and then a short (18") USB-C cable from the harness to the device mounted right below the IPMA on the windshield. This is a good time to note that the Comma does not actually communicate USB; it is only borrowing a USB cable because of the nice convenient form factor to act as an extension cable for the Canbus networks (this is why the cable specification for Comma is so strict, USB3.2gen2 cables only. lower spec cables don't have all of the pins terminated). To get power to the Comma on the windshield, they ran a long cat5 cable (which has recently been replaced by a 4-pin cable) from the ODB port under the dash to the rearview mirror mounted harness.

When Ford introduced BlueCruise the new IPMA was much more powerful and too large to fit under the rearview mirror cover. For the F150/Lightning/Expedition, it was moved under the dash near the driver's foot, and for the MachE it was placed in the trunk. Comma was of no mind to redesign their whole philosophy to accommodate this change, so they just said, "Use a long USB cable and a short CAT5 cable". This philosophy worked out fine for the F150 and the MachE, but when the Lightning guys started installing a Comma, they ran into issues with the Canbus network that generated the annoying errors.

The heart of the issue is that the long USB-C cable creates a 10-foot-long unterminated stub on the Canbus network, and when the Lightning cranks up it sends out a blast of electromagnetic frequency (EMF) that causes the Canbus communications to be corrupted briefly. To remedy the issue, the extension harness is built, which moves the black box up to the rearview mirror, where it was planned to be based on Comma's initial designs. The two resistors are added across CANBUS-1 positive/negative and CANBUS-2 positive/negative so that the long Canbus wires are no longer unterminated. These resistors prevent the EMF blast from corrupting the communications.

When the harness is completed, the black box moves up to the rearview mirror so you now need a short USB-C, and a long power wire (the 4 pin connector). Technically, you can get by without installing the ODB adapter and the power cable, it just means that the comma will power off between drives and it will take 2-3 minutes to boot up once you start driving.

Got it, so the 4 pin connector will need to be extended if I extend the box up under the mirror or I run without it.

 

[JerseyMike]

any idea what the 4 pin is called, wondering if it is standard and I can just buy a cable to extend it

 

[Ajzride]

any idea what the 4 pin is called, wondering if it is standard and I can just buy a cable to extend it

it's some kind of ATX, but I'm not positive which. I would just cut it and use the solder seals to extend it using what is left over from the harness extension wiring. It's just power so there is no concern with noise.

 

[watts/up]

I guess this is a good time to give a lot of background information, some of which you may already know but could be good for others in the future, to help everyone understand how this works and what the problem is.


The way Comma and OpenPilot work is by intercepting the Canbus communications between the Image Processing Module (IPMA) and the Power Steering Control Module (PSCM). The communications from the IPMA are blocked, and the Comma pretends to be the IPMA and sends its own signals to the PSCM. This is what we call a man-in-the-middle attack in cybersecurity circles. To accomplish this. The comma has to physically break the Canbus network in a place that Comma is certain it can block those communications between the two modules. The only two places this is certain are at the inlet of the PSCM (which is usually under the hood near the steering rack) or at the output of the IPMA. Prior to hands-free driving platforms (BlueCruise, SuperCruise, FSD), the IPMA was almost exclusively located under the rear-view mirror cover. Since the Comma needs to be mounted very close to the rearview mirror to see the road and watch the driver, this made intercepting the Canbus networks at the IPMA the ideal scenario.

This means that 90% of cars that comma works with (including Fords that use the older lane centering technology like Maverick, Explorer, Escape) have a harness that intercepts the Canbus near the rearview mirror, and then a short (18") USB-C cable from the harness to the device mounted right below the IPMA on the windshield. This is a good time to note that the Comma does not actually communicate USB; it is only borrowing a USB cable because of the nice convenient form factor to act as an extension cable for the Canbus networks (this is why the cable specification for Comma is so strict, USB3.2gen2 cables only. lower spec cables don't have all of the pins terminated). To get power to the Comma on the windshield, they ran a long cat5 cable (which has recently been replaced by a 4-pin cable) from the ODB port under the dash to the rearview mirror mounted harness.

When Ford introduced BlueCruise the new IPMA was much more powerful and too large to fit under the rearview mirror cover. For the F150/Lightning/Expedition, it was moved under the dash near the driver's foot, and for the MachE it was placed in the trunk. Comma was of no mind to redesign their whole philosophy to accommodate this change, so they just said, "Use a long USB cable and a short CAT5 cable". This philosophy worked out fine for the F150 and the MachE, but when the Lightning guys started installing a Comma, they ran into issues with the Canbus network that generated the annoying errors.

The heart of the issue is that the long USB-C cable creates a 10-foot-long unterminated stub on the Canbus network, and when the Lightning cranks up it sends out a blast of electromagnetic frequency (EMF) that causes the Canbus communications to be corrupted briefly. To remedy the issue, the extension harness is built, which moves the black box up to the rearview mirror, where it was planned to be based on Comma's initial designs. The two resistors are added across CANBUS-1 positive/negative and CANBUS-2 positive/negative so that the long Canbus wires are no longer unterminated. These resistors prevent the EMF blast from corrupting the communications.

When the harness is completed, the black box moves up to the rearview mirror so you now need a short USB-C, and a long power wire (the 4 pin connector). Technically, you can get by without installing the ODB adapter and the power cable, it just means that the comma will power off between drives and it will take 2-3 minutes to boot up once you start driving.

This makes much more sense now, thanks! Appreciate the thorough explanation.

 

[JerseyMike]

it's some kind of ATX, but I'm not positive which. I would just cut it and use the solder seals to extend it using what is left over from the harness extension wiring. It's just power so there is no concern with noise.

ok, and low voltage I assume?

 

[Ajzride]

ok, and low voltage I assume?

12 volts DC, less than 0.1 amp.

 

[JerseyMike]

12 volts DC, less than 0.1 amp.

Thanks,

thinking of 2 options for the 12 wire:

unshielded: https://a.co/d/hMMezDH


shielded: https://a.co/d/7N7R3GH



the unshielded I like because it seems like a higher quality wire and black loom....also ships faster but shielded not much more expensive.

 

[Ajzride]

Thanks,

thinking of 2 options for the 12 wire:

unshielded: https://a.co/d/hMMezDH


shielded: https://a.co/d/7N7R3GH



the unshielded I like because it seems like a higher quality wire and black loom....also ships faster but shielded not much more expensive.

The shielded wire you linked is exactly what I have been using. I recommend waiting for the shielded wire.

 

[evowner]

Maybe a ferrite bead would help better than shielded cable. If it is EMF vs RF. Where are you connecting the shield? If not terminated properly it can become an antenna.

 

[Ajzride]

Maybe a ferrite bead would help better than shielded cable. If it is EMF vs RF. Where are you connecting the shield? If not terminated properly it can become an antenna.

Possibly. As a chemical engineer, I am on the very fringe of my understanding of these things. I can simply say I've made about a dozen from the shielded cable and there have been no issues.

 

[JerseyMike]

ok, so before ordering I removed the harness and everything from my truck.

Good news: looks like the power plug (4 wire) is long enough to reach so no need to extend that

bad news: when I look at the connector the new style appears to have 14 wires that I have to extend instead of 12.... 2 of each of the following: green, orange, brown, pink, black, blue, and Grey.

is anyone else seeing this with the new q4 harness?

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