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Discussion Starter · #1 ·
Hi All,

I've had my Mazda 6S MT for three weeks now, and I love it. I am interested in car computers and networks, so I wanted to see what I could get out of the CAN bus in our car. I purchased a ValuCAN USB interface, along with a OBD-II cable from Intrepid Control Systems. After installing the software on my laptop, I connected it to the car and started getting a lot of data like this (paraphrased):

Line Abs Time Arb ID B1 B2 B3 B4 B5 B6 B7 B8
1 1.83059 201 0 0 FF FF 27 10 0 FF
2 1.83083 211 FF FF FF FF 0 FF FF 38
3 1.83106 215 2 3 2 3 2 28 12 0
4 1.83171 200 FF FF FF FF FF FF 3 0
5 1.83192 231 F 0 FF FF
6 1.83213 240 0 40 80 33
7 1.83229 650 0
8 1.83364 4B1 0 0 0 0 0 0 0 0
9 1.83415 4B0 27 10 27 10 27 10 27 10
10 1.83763 210 FF FF 38 4 0 0 0
11 1.84142 201 0 0 FF FF 27 10 0 FF
12 1.84167 4B1 0 0 0 0 0 0 0 0
13 1.8419 215 2 3 2 3 2 28 12 0
14 1.84215 4B0 27 10 27 10 27 10 27 10
15 1.84664 211 FF FF FF FF 0 FF FF 38
16 1.84964 4B1 0 0 0 0 0 0 0 0
17 1.85015 4B0 27 10 27 10 27 10 27 10
18 1.85052 201 0 0 FF FF 27 10 0 FF
19 1.8508 215 2 3 2 3 2 28 12 0
20 1.85363 210 FF FF 38 4 0 0 0
21 1.85737 200 FF FF FF FF FF FF 3 0
22 1.85764 4B1 0 0 0 0 0 0 0 0
23 1.85781 231 F 0 FF FF
24 1.85802 240 0 3F 80 33
25 1.85826 4B0 27 10 27 10 27 10 27 10
26 1.86059 201 0 0 FF FF 27 10 0 FF
27 1.86087 215 2 3 2 3 2 28 12 0
28 1.86264 211 FF FF FF FF 0 FF FF 38
29 1.8641 430 40 95 0 0 0 CC 0
30 1.86564 4B1 0 0 0 0 0 0 0 0

From watching the data change, I have been able to decode some of the fields. ID 201, for instance, contains RPM in the first two bytes, speed in bytes 5 & 6, and accelerator position in byte 7. ID 215 has throttle position in byte 7. Engine coolant temperature is in 240, byte 2. It also seems to be in 420, byte 5. Fuel level is in 430, byte 1. There are two fields that increment when the car is moving and roll over at FF (odometer like). They are 420, B2 and 4C0, B1. 4B0 and 4B1 contain the speed of each wheel (two bytes per wheel). In 4B0 it is offset by 10000.
That's all I have been able to figure out so far. I haven't tried to transmit anything yet, because I don't have any idea what to send. I'm sure there are some diagnostic commands that can be sent to get additional data. I look forward to hearing from anyone else who has tried this.
 

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Reading Topic: Decoding the CAN bus

k i read it as well as i could and i gathered that with all that information decoding and analysing...that you might be able to input your own data into the car somehow???"I haven't tried to transmit anything yet, because I don't have any idea what to send"

Maybe you could tell everyone that isnt a computer programmer what the advantages of doing this activity is? Sounds interesting though
 

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Discussion Starter · #4 ·
Replying to Topic 'Decoding the CAN bus'

QUOTE
Originally posted by stevesteve


Maybe you could tell everyone that isnt a computer programmer what the advantages of doing this activity is? Sounds interesting though[/b]
How about using it to see if that grounding mod made any difference in the throttle lag...

 

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Reading Topic: Decoding the CAN bus

CANman, I'm going to be the first to give you a HUGE thank-you for what I can surely see will become absolutely great information for us to have.

:cheers
 

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Replying to Topic 'Decoding the CAN bus'

QUOTE
Originally posted by CANman


            QUOTE
Originally posted by stevesteve


Maybe you could tell everyone that isnt a computer programmer what the advantages of doing this activity is? Sounds interesting though[/b]
How about using it to see if that grounding mod made any difference in the throttle lag...

[/b][/quote]


could you explain these graphs, I'm not sure which one is stock, which one is moded etc...nice job BTW, I'm sure that took some work.
 

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Discussion Starter · #10 ·
Reading Topic: Decoding the CAN bus

All the graphs were from the same set of data, just displayed in different ways. This was accelerating onto the freeway (uphill) and there is no grounding done. All graphs show the gas pedal position in green. The first graph shows the throttle position in violet. There isn't much lag there. The second graph shows the engine RPMs in violet. You can see a little bit of lag, especially at the second shift.
The software I used for this was Vehicle Spy from Intrepid Control Systems. A 5 day evaluation was included with the interface. My 5 days is up already, so I will have to start writing my own software :(
 

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Replying to Topic 'Decoding the CAN bus'

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Originally posted by mazda16


            wut the hell does that mean[/b]
CANman, You are the best! :hoho

I had to read these kind of graphs while in college. :D

All three graphs show the same event. It shows the relationships between the accelerator (gas) position and three other variables. Note that the green line shows accelerator position (0 to 100%) as the same in all three graphs.

Graph #1 shows how the throttle position is affected in real time by actions of the accelerator pedal. It can tell us if the throttle position lags in response to the accelerator pedal.

Graph #2 shows the reaction of the engine to the accelerator pedal. This can tell us the engine's responsiveness to the accelerator. Any throttle position lag time would be a component of this measure.

Graph #3 shows the speed of the car affected by the position of the accelerator pedal. There are many drag/race applications with this graph.

Since the graphs are "zoomed" out too far, it is hard to actually to conclude anything. Is there someway of getting read outs in milliseconds rather full seconds?

Please post more! :)


-SC3
 

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Replying to Topic 'Decoding the CAN bus'

Oops, previous post was 12 seconds too late.

BTW, how much does Vehicle Spy sell for?


-SC3
 

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Discussion Starter · #13 ·
Replying to Topic 'Decoding the CAN bus'

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Originally posted by SC3


Since the graphs are "zoomed" out too far, it is hard to actually to conclude anything.  Is there someway of getting read outs in milliseconds rather full seconds?

Please post more!  :)


-SC3[/b]
The data is coming in every 10 milliseconds, so it is possible to get quite good resoluiton.
 

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Reading Topic: Decoding the CAN bus

CANman, thanks.

I'll be purchasing the same hardware/software. This looks so damn interesting it's making my ass twitch. I can't wait.

Do you recommend the product from valuecan.com?
 

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Replying to Topic 'Decoding the CAN bus'

Damn, the VehicleSpy software costs $1995 USD! :(

QUOTE
Taken from http://www.valuecan.com/http://www.valuecan.com/[/i]

Software Support: Turn-Key or Create Your Own

First, ValueCAN comes with a simple analyzer to monitor your messages: Vehicle Spy CE. This simple analyzer will let you connect to ValueCAN, monitor Controller Area Network traffic, pause messaging, save Excel compatible trace files, and transmit simple messages.

The professional user will want to upgrade to the full Vehicle Spy software. The Vehicle Spy software lets you filter Controller Area Network traffic, decode message data, build scripts, simulate other nodes, and build graphical displays of your data.  

For those of you who want to write your own Controller Area Network applications ValueCAN includes a DLL and helpful examples are included for Visual C++, Borland C++ Builder, LabWindows CVI, LabVIEW, and Visual Basic. For more information on the DLL please see the neoVI DLL documentation (ValueCAN uses the neoVI DLL).[/b]
The DLLs and documentation are available, so it shouldn't be too hard to write my own CAN applications. :)


-SC3
 

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Replying to Topic 'D

QUOTE
Originally posted by CANman
My 5 days is up already, so I will have to start writing my own software :([/b]
Do the world a favor and write it in Java and open source it on sourceforge :D (edit: screw the DLLs)
 
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