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The "sync" that you refer to with the new sensor is actually a calibration that has to be done for all new sensors. Moving a sensor from one car to another is seamless, and does not require any activity.

Replacing the mat circuit is what i looked at doing first. That seemed to be the simplest part to duplicate, but there is virtually no way to connect your new circuit to the existing one because of the delicate nature of the printed circuit and everything in the electronics box being potted. You may have better techniques, but I gave it up as un-feasible.

The communication between the sensor and the SDM is not CAN. It is a single-wire serial protocol that doesn't seem to match anything that any of the system programmers I know recognized. I did a brute force read-and-copy of the data that is transmitted back and forth under different circumstances and programmed an arduino to mimic the sensor. It works about 95% of the time, but occasionally the start-up handshaking fails and I get the service airbag message. It clears itself the next time I power the system but it is still pretty annoying, and something that has to be watched for every time you power the car.
 

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What is the cost of something like this. I could put up with the 5% as my Lexus already make me push a button to acknowledge that I wont use the GPS while driving before I drive off so shutting down and restarting the Sky occasionally would not be a problem and most of the time the right seat would be empty anyway. My wife died Saturday so she wont be using it and I cant imagine ANYONE taking her place, at least for many years.
 

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Discussion Starter · #1,083 ·
Right but if you keep the controller box thats attached to the seat film in place, the car checks with the box on power on. If the circuit of webbing is not broken there will be no errors. If you keep the box in place and make a new webbing circuit with the same resistance values, the seat controller won't know any different. There is no logic in the webbing, it's just ribbon cable and carbon pressure switches. The hardest part would be connecting a new circuit in place of the ribbons since they cannot be soldered to, you would almost need some solder paste or something that can be fused to it.
Very true. You would just have to have weight values and the overall weight pattern mimic what the control box is looking for in order to send the proper instructions to the main air bag controller to turn the passenger air bag on.

I think JohnWR just was going to bypass the PSS controller completely rather than trying to spoof it. He got really far. I anxiously await to see what you guys discuss. I get the overall picture of it, but know nothing of the nitty gritty stuff to make these things work. John does...and it sounds like you do too...so it should be an interesting talk.
 

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Discussion Starter · #1,084 ·
The "sync" that you refer to with the new sensor is actually a calibration that has to be done for all new sensors. Moving a sensor from one car to another is seamless, and does not require any activity.

Replacing the mat circuit is what i looked at doing first. That seemed to be the simplest part to duplicate, but there is virtually no way to connect your new circuit to the existing one because of the delicate nature of the printed circuit and everything in the electronics box being potted. You may have better techniques, but I gave it up as un-feasible.

The communication between the sensor and the SDM is not CAN. It is a single-wire serial protocol that doesn't seem to match anything that any of the system programmers I know recognized. I did a brute force read-and-copy of the data that is transmitted back and forth under different circumstances and programmed an arduino to mimic the sensor. It works about 95% of the time, but occasionally the start-up handshaking fails and I get the service airbag message. It clears itself the next time I power the system but it is still pretty annoying, and something that has to be watched for every time you power the car.
Wholly crap I actually remembered something correctly! Its a miracle! LOL Shame there wouldn't be a way to do some kind of warm reboot on the whole system after the car was started to retry the handshake.
 

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What is the cost of something like this. I could put up with the 5% as my Lexus already make me push a button to acknowledge that I wont use the GPS while driving before I drive off so shutting down and restarting the Sky occasionally would not be a problem and most of the time the right seat would be empty anyway. My wife died Saturday so she wont be using it and I cant imagine ANYONE taking her place, at least for many years.
I haven't really defined a cost since there are several things that need to be worked out before I would sell one. The cost of the hardware is pretty low, but I have hundreds of hours in development time decoding the communication and writing the program. Honestly, with GM finally bowing to the pressure for the recall, and following through with replacements (even if they aren't really doing the right thing in all cases) I haven't seen a true need for it. If GM does eventually wash their hands of us, then I will look at that again. In any event, my lawyer has kittens every time I mention the idea to him, so there is that aspect too.

It is sad to hear that you lost your wife.

Wholly crap I actually remembered something correctly! Its a miracle! LOL Shame there wouldn't be a way to do some kind of warm reboot on the whole system after the car was started to retry the handshake.
You probably could do that by putting a momentary normally closed switch in the power to the SDM, but I have tried to monkey with as few pieces of the system as possible. What I have learned to do is power the car, wait for the airbag system to go through its start-up procedure, then start the engine.
 

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Jim, I am very sorry to hear the bad news. I seemed to notice you really haven't been yourself the last couple of weeks. Hope we can somehow take your mind off it a little.

JohnWR seems to be our only hope on something working.

Again very sorry to hear of your loss.

Bob
 

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the car was hers so i will never sell it. but it will be awhile before anyone else occupies the passenger seat. thanks for the sympathy. its another pothole in the road. but life is a one way street so you never hit the same pothole twice. thank God
 

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What is the cost of something like this. I could put up with the 5% as my Lexus already make me push a button to acknowledge that I wont use the GPS while driving before I drive off so shutting down and restarting the Sky occasionally would not be a problem and most of the time the right seat would be empty anyway. My wife died Saturday so she wont be using it and I cant imagine ANYONE taking her place, at least for many years.
I don't know how I missed this yesterday. I'm so very sorry to hear of your loss.

:sad:

.
 

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Sorry for your loss. My Sky was originally the wife's car. Then I lost my wife a couple years ago after 42 years. The strange thing is unknowing to me before she passed she paved the way for me to get back with my old high school crush. Life can through you some curves but we are all just along for the ride.
 

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Right, thats the "sync" part I was referring to. I think it has to do with using the CAN bus. An easy way would be to map those pressure points and input their resistance into your vehicles specific seat controller box, that way its already synced and all you are doing is making switches.
They are NOT pressure sensors and have no 'resistance' to emulate. They are capacitance sensors in a matrix. You cannot emulate the mat itself, only emulate the controller interface to the car's GMLAN - which is what John was doing.

The sensor mechanism is described earlier in this thread somewhere (or in the Solstice thread).
 

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They are NOT pressure sensors and have no 'resistance' to emulate. They are capacitance sensors in a matrix. You cannot emulate the mat itself, only emulate the controller interface to the car's GMLAN - which is what John was doing.

The sensor mechanism is described earlier in this thread somewhere (or in the Solstice thread).
Why do you think a capacitance matrix can't be copied? More difficult to measure, perhaps, but if someone builds it, someone else can usually copy it.

And yes, this is being picky, but it isn't on the GMLAN. Communication from sensor to SDM is serial.
 

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Agreed, even if it's capacitors it's all essentially an analog signal as voltage going into a processor. I think it the mat could be emulated.
 

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Why do you think a capacitance matrix can't be copied? More difficult to measure, perhaps, but if someone builds it, someone else can usually copy it.
Of course you are correct John. Now go ahead and see how long it will take you to reverse engineer that resin encapsulated circuitry in the controller box, dis-assemble the software and then come up with an emulator for the mat.
 

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Of course you are correct John. Now go ahead and see how long it will take you to reverse engineer that resin encapsulated circuitry in the controller box, dis-assemble the software and then come up with an emulator for the mat.
Sarcasm aside, you are absolutely correct. That approach would be nearly impossible, and I wouldn't even try it.

The thing is, though, that when emulating something you don't care what it is, you care what it does. So there is no need to disassemble or reverse-engineer any of the existing electronics. Everything that needs to be done can be done externally, by measuring, observing, and analyzing the inputs and outputs.

If I was going to replace the mat, but keep the electronics, I would start by tracing the mat's circuits to determine which of the "wires" going into the electronics were paired. As we all know, finding a way to connect to the flexible circuitry would be a major challenge, but there probably is a way to do it so i will assume that it is possible. Having connected to the circuits I would then analyze them to be able to duplicate their resistance, capacitance, and maybe even inductance in both the occupied and unoccupied conditions. By supplying these same values to the electronics it would be possible to make it believe that it is connected to an actual mat, and the problem would be solved. Simple, right?

You might remember when these discussions started several years ago, I advocated for replacing the mat, thinking the hardware would be easier to duplicate than the electronics/communications. You actually convinced me otherwise and started me on the road that I ended up following. You turned out to be correct, and emulating the communication between the PPS electronics and the SDM turned out to be fairly straightforward, if not exactly easy.

The emulator that I built plugs into the seat harness, communicates with the SDM, and controls the airbag on and off lights, just like the PPS did. About 95% of the time. Occasionally it gets confused and the system faults. I did take the easy way out, and decided to avoid development of a sensing mat as there are a number of different pressure mats on the market. I provided an input to my emulator that uses a dry contact to tell it whether the seat is occupied, and I am currently using a dash-mounted SPST rocker switch for that purpose.

Does anyone know what the sensors look like they installed after the recall? Has it been revised without a ribbon between the 2 pads?
I haven't seen one yet, but give me about a month and I will have two of them.

What I have understood is that the new sensor mat is exactly the same as the old sensor mat, but has had a layer of heavy tape applied to it to provide more strength and therefore resist the bending that caused the original mat to fail.
 

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Discussion Starter · #1,099 ·
Just looking at some of the patents maybe help on how the analog side works. I haven't found the exact GM one yet but heres an example. VEHICLE SEAT WITH CAPACITIVE OCCUPANT DETECTION SYSTEM
The manufacture of the sensor mat itself is IEE Luxemburg. They made these kinds of mats for a number of auto manufacturers including BMW, Mini, Kia, and Suzuki. Each platform has a slightly different layout to the mat and it's sensors but they all use the same basic layout and premise.

Here is the layout from the patent I found back when I wrote my White Paper. IIRC, this is from IEEs patent on their mat that is in our cars. The area labeled sensor mat in the image is the part that fails and all the round numbers in the mat represent the individual pressure sensors.

You see raw sensor data is sent to two modules, one calculating weight and the other calculating pattern. However, weight info from the Weight module also feeds into the Pattern Module. This is how we have determined that the Decision Making Module, which is what signal comes out of the PPS and heads off to the Air Bag master controller (I think this is the SDM John is talking about), uses the pattern of how much weight and the way that weight is distributed across the sensor mat to determine the on or suppress command to the SDM. However, everything you see below makes up the PPS mat in our cars.

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JohnWR said:
What I have understood is that the new sensor mat is exactly the same as the old sensor mat, but has had a layer of heavy tape applied to it to provide more strength and therefore resist the bending that caused the original mat to fail.
You are correct John. The overall design of the sensor mat itself remains unchanged except for the addition of a reinforced plastic tape placed on the outside of the protective black covering that encases the actual sensor matrix itself. It has the affect you describe in that it highly reduces the ability of the flexible areas of the sensor matrix to fold over on itself, bend and kink, and then damage that area of the matrix. It is this folding over and kinking that is the root of our failures.
 
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