It's a differential pair, similar to RS485 which in turn is RS422 on two wires instead of four, i.e. half duplex instead of full duplex

The ABS module shouldn't need to be on the CAN Bus at all in order to operate. It should be able to operate entirely on its own. Indeed, the only reason it even needs access to the CAN Bus at all is malfunction lights.

It needs to be on CAN to send/recieve signals from other modules that it relies on for vehicle info like vehicle speed, ignition status etc. ABS will not work without these signals.

@@ethompson526 ABS will work just fine without those signals. ABS predates CAN by over a decade fun fact. Mercedes was putting it in the S class in the late 70s, GM was putting it in select high end Caddies in the early 80s, and by 1990 p.much anything that wasnt the lowest trim vehicle on the showroom had at least rear wheel ABS. CAN didnt come around until OBD II in the mid 90s, and even then, CAN integration was minimal. ABS didnt really start talking on CAN until the early 2000s when everything started getting other driver's aids that also used wheel speed sensor data. Moreover, there are ABS retrofit kits available for classic cars that are 100% stand alone and are designed to work in a car that is otherwise electrically unmodified. You could put ABS on a 1929 Ford Model A if you wanted to. Ignition status is irrelevant. ABS should be active any time the car is moving whether the ignition is on or not. An ignition switch failure should not mean ABS no longer works. Can also be derived from the simple fact that the fucking module has power in the first place if one wants to avoid another quiescent current draining the battery; if the module is on it knows ignition is also on. ABS is where vehicle speed data is collected these days. It does not need access to CAN to know how fast the car is going. It operates by measuring the speed of each wheel and comparing across the car looking for a discrepancy indicating a locked brake, so by virtue of how it operates, it already has that data. CAN needs ABS to report vehicle speed to the driver but ABS doesnt need CAN since it is collecting that data directly anyway. ABS is perfectly capable of collecting all the data it needs to function without any CAN whatsoever.

@@TestECull With respect, I think you are looking backwards too much. I agree ABS in one of its various guises has been around for many many years. That said each system was quite proprietary and implemented entirely according to the vendors whim. I see the introduction of CANbus as an enabler to bring, not just ABS but, all those vehicle management functions together over one common resilient transmission media, I'e. Why have multiple systems?

@@boldford Part of why I refuse to buy modern cars is how ridiculously interconnected they are. I should not have to worry about a blown out speaker causing a no crank no start fault, and it won't in older cars because the radio is completely standalone. But on these modern ones the radio is on CAN and if the blown speaker takes out the wrong chip in the head unit it will flood CAN with garbage data that drowns out all the other sensors and such the vehicle needs to run. erego, a speaker failure can take the entire car offline these days. ABS has no need of CAN and should be perfectly capable of functioning on its own as it used to do. If we're going to insist on coddling the morons on the road by throwing ADAS at their bad driving instead of actually solving the root problem, let's at least make sure those various systems can and will function entirely independently of anything else on the car.

They can probably be any combination of wire colors. This ford I’m on has white and blue for high speed can. They can use other for can low. Depends on manufacturer you’ll have to study a wire diagram for the application

Sobering

Good times.

When you're not and clicking on the right video...just as much fun.

What doesn’t kill you makes you stronger I guess

I became an engineer by tokin' and cruisin' the internet.

Reflections are minimised by having a terminating load that matches the characteristic impedance (a.c. resistance) of the cabling. In radio systems, this effect is specifically tested for during cable installation to ensure maximum forward power, i.e. minimum return loss.

Yes, the 0 needs to be a "dominant" bit during arbitration or packet collision. One way of achieving this with potentially multiple device driving the bus is to let the recessive nodes with their 1 remain passive (i.e. no voltage difference, or hi-Z) while the dominant node(s) force a difference with their 0 bit value.

Hi, do you know what is that ?

Yes no problem, you just need to make sure that a node with a termination resistor (if enabled) is placed at the end of the bus.

The High line will be steady @ 2.5V and the Low line will be steady @ 0v

@@1963TOMB Any reference to official doc? According to the guide both lines should be at 2.5 V

Hi, Thank you for the comment. I believe that you are confused between high speed CAN ISO 11898-2 (the subject of this video) and low speed CAN ISO 11898-3.

I recommend reading the TI application notes SLOA101B and SLLA270. It is heavy reading, but full of gold if you dig into it.

The 30cm refers to the maximum stub length and not the overall bus length.

@@hardwireelectronics3835 30 cm seems awfully short even for a car - about a foot. If that is true, these devices need to be carefully used.

@@donmoore7785 Why would a stub need to be longer than 30 cm?

@@donmoore7785 30cm is the max distance of any node to the bus, not the maximum length of the bus.

I don't think that is necessarily pedantic; it's a fair point to raise. He gave that example, I think, because he's referring to external induced noise (EMF) not inherit line noise (which would be symmetrical on both lines by design if the noise is internal to the transceiver or just a fault if one line is electrically impacted by physical short-circuit or open load type faults), raising the line active level far away from the noise floor actually does mitigate this external noise but in a naïve way (no disrespect intended), if the actual operational context of the ECU is not considered. It's much, much more complicated than "just two wires" might lead some to believe, however this isn't hobby level electronics we're talking about and communications in an automotive setting need to actually be guaranteed to a minimum automotive standard (can't remember the ISO number of the top of my head) and depending on the use of the actual signals traveling on those lines, the SW part, at least, of that CAN implementation is held to higher and higher standards such as levels on the ASIL standards (safety standards) as well as (newer) cyber security standards which in the EU at least, will be mandatory by law, in any new ECU sold after mid 2024, if I remember the year correctly. And, regardless, if the operating conditions of a vehicle exposes it to such a high induced external noise on balanced lines, then, even though I'm no expert, it may be that the wrong CAN type is used (in this case "normal" CAN or CAN-HS - high speed or CAN-FD - flexible data rate) so one might use the CAN-FT - fault tolerant - bus that has the lines go from -27V to +40V or even a terminating bias CAN that has power and ground cables besides the two data lines that provides the same electrical bias and terminations for each bus segment, and this is just scratching the surface of the physical layer of the standard with no mention of errors/collisions/bit timings/ bit sampling/faults mitigation happening in all the other layers of an actual CAN com stack.

Like the green kind? Lol

PDM.. power distribution module

vocal practice needed