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littlefeck

G4+ Mazda RX8 CAN Bus

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A brief google suggests there might be a chance of getting it to work.  Taken from this page here:  https://www.cantanko.com/rx-8/reverse-engineering-the-rx-8s-instrument-cluster-part-one/  the below info suggests just those first two ID's would give you a working dash.  500Kbit/sec rate.  I dont have enough experience with OEM CAN conventions (if there are any) to know what the byte order will likely be but trial and error will probably work that out.

If you have a car fitted with a G4+ and its already running and connected to the CAN bus then I can give you a couple of examples to try.

DJqcd0M.png

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This guy has a really good process on how to observe and reverse engineer canbus signals

http://bobodyne.com/web-docs/robots/MINI/CAN/MINI_CAN.pdf

His example use a mini but the process applies to everything. Its basically push the car through some known states eg press gas pedal, speed up, slwo down, turn steering wheel. Graph the output of each stream of data coming across the can bus, then try to map what you did to something you can see happening on the canbus.

I've done this myself on a subaru using one of these

https://www.aliexpress.com/item/Dual-Channel-USB-To-CAN-Analyzer-DeviceNET-iCAN-VRMS-CANOpen-J19339-CAN-Analyzer/32359550686.html?spm=2114.search0104.3.1.TSYAka&ws_ab_test=searchweb0_0,searchweb201602_4_10152_10065_10151_10344_10068_10345_10342_10547_10343_10340_10341_10548_10541_10084_10083_10560_10307_10175_10060_10155_10154_10056_10055_10539_10537_10312_10536_10059_10313_10314_10534_10533_100031_10103_10073_10102_10557_10142_10107,searchweb201603_25,ppcSwitch_5&btsid=c137e58f-7221-4cd6-8e73-88f833c9f482&algo_expid=3d31339c-5443-452b-a5c7-85399dba71d8-0&algo_pvid=3d31339c-5443-452b-a5c7-85399dba71d8

It looks really daunting to start with as literally nothing has labels, but as soon as you get your head around which devices are which ID's you can start to focus on things that matter - eg tacho signal has to come the ecu, speed has to come from the abs computer (check wiring diagrams but this is usually true) so you have a pretty good idea where to look, graph each block of data, then look for a graph pattern that matches what you did with the vehicle, then work out the scale of it. You may want to start by watching the ID's that are present and the time intervals of them and disconnecting abs/ecu/body control computer/etc to start with as the first step. Remember you dont have to understand all of it, just the signals you are sending from the ecu or receiving via canbus (eg speed)

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@Adamw Hi Adam, I am currently trying to configure the CAN bus on my base map but am having some difficulty making sense of the example data to plug into it. Also is it possible just to send a frame of data to keep the power steering working -

200 00 00 FF FF 00 32 06 81 // EPS doesn’t work without this

202 89 89 89 19 34 1F C8 FF // EPS doesn’t work without this

http://www.madox.net/blog/projects/mazda-can-bus/ has additional information but I cant make sense of the ID that sends individual wheel speed (link ECU receives)

000004B0 0,1     Left Front Wheel Speed Check Order. Scale = (X-10000)/100 km/h, unsigned (Refer to handle position). Correlates with 00000020F vehicle speeds.
000004B0 2,3     Right Front Wheel Speed Check Order. Scale = (X-10000)/100 km/h, unsigned (Refer to handle position). Correlates with 00000020F vehicle speeds.
000004B0 4,5     Left Rear Wheel Speed Check Order. Scale = (X-10000)/100 km/h, unsigned (Refer to handle position). Correlates with 00000020F vehicle speeds.
000004B0 6,7     Right Rear Wheel Speed Check Order. Scale = (X-10000)/100 km/h, unsigned (Refer to handle position). Correlates with 00000020F vehicle speeds.
000004DA 0,1     Steering Column Angle (X-32768)/10 Degrees, Clockwise +ve.

 

The id is shown above as 000004b0 but the ID in the ECU is numerical only.

I have attached my base map and am using CAN bus 2

 

 

 

rx8.pclr

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So this will work for getting the wheel speeds to the ECU rather than via the DI's? 

Id like to save these inputs if possible.

Also is there a way to turn the termination resistor off to turn the ECU into an node as i am planning to add another device to input CAN signals to the dash which already has the terminator built in.

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yes, this will receive wheel speeds via CAN.  The termination resistor can only be removed (unsoldered) but try it as it is at present, I have had systems work fine with 3 resistors connected before.

also attached an updated map that has a bit more CAN bus dash functionality set up.

RX8 CAN example.pclr

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Wow. That's awesome, nice work!

I'm a total noob when it comes the CANbus so what exactly does this send to the dash?

looks like you have added oil pressure, but what are the VA8 outputs in stream 4? That virtual output is turned off. are they used to turn off other warning lights?

Things I require are:

RPM

Charrge

Speed inc Odometer

Check engine light 

Cruise on light

Coolant temp

Oil pressure (via ANV input 10bar sensor) ( i know the dash works off a switch but can the ecu output at say 25psi and above or something?)

This will be for my RX8 running a 1JZ VVT-i using the RX8 e-throttle with Aircon.

Ive attached my installer IO. Planning to run a Fury and it would be nice to save on some of the AUX outs and DI's.

 

ECU-IO (1).pdf

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The VA8 is just used to generate a constant.  VA8 cannot be used for anything else and must remain set to off for this to work.

I can't confirm if the ODO works as I haven't had feedback from anyone on that.

The cruise light wont work but everything else you mention should.

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4 hours ago, Dannobre said:

Does anyone have the CAN iD  for the clutch switch, Brake pedal,  Neutral switch  or is it just easier to hard wire them?

 

Both of those inputs are directly sent to the ECU

Neutral - pin 2O

Brake - Pin 4P

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