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Discussion Starter · #21 ·
Replying to Topic 'Decoding the CAN bus'

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Originally posted by Arcanlaw


            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?[/b]
There are cheaper interfaces, like this one, but they can't keep up with the data rate (500kbps) in our car. The ValueCAN costs $295 plus $25 for the OBD-II cable. It's a decent product.
 

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Reading Topic: Reading Topic: Decoding the CAN bus

Link doesn't work. :)

I'm not sure if the application I plan to write can keep up with 500kbps, broadband speed I think. I hope the DLLs have a good buffering capability.


-SC3
 

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Discussion Starter · #23 ·
Reading Topic: Reading Topic: Decoding the CAN bus

I fixed the link (forgot about the ampersand issue).

The DLL does seem to have good buffering.
 

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An old thread I know but it came up in a search.

We've just bought a Mazda6 MPS (aka MazdaSpeed6), coming from an RX-8.

I spent some time playing with the CAN in the RX-8 and decoded a lot of it, you don't need expensive software or hardware although it makes life easier as someone has done the hard work for you. A plain el-cheapo ELM327 off the bay will do, you just need to up the speed and set a few options.

I won't go though all the details, I did document it if anyone is interested. Have a read of the stuff I posted under the category 'CAN' CAN | Druids Blog

To sum up though you'd need the following sequence of commands on an ELM327
AT PP 0C SV 11
AT PP 0C ON
AT Z
(reconnect at new speed)
AT CAF0
AT V1
AT S0
AT D1

Then to start the capture:
AT MA

I've yet to have a play in the MPS (mostly because my laptop battery is dead) but I'll post to my blog when I have. I'd be interested if anyone knows the CAN id for boost level though! :)
 

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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.
Hi CANman, thank you very much for your sharing! How you know 4B1 contain the speed of each wheel (two bytes per wheel)?
 
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