I was curious if we had anyone who is experienced in CANBUS? As some may know, the S2 RX8 makes more valuable use of the MS-CAN bus for things like the AC, Radio, Headlights, etc. I believe on older Gen models there was a mix of MS-CAN use and SPI use.

This bus, along with the HS-BUS which houses more critical information like rpms, and engine temps, etc can be accessed from the OBD2 port. The HS(+/-) and MS(+/-) busses can be tapped into via pins 6/14, and 3/11 respectively.

This is very similar to the GM based protocol called GMLAN. If my assumption is true, that means there would have to be a BCM on board which would act as a gateway between the MS and the HS bus. This would mean that any data that sits on the HS bus can be accessed from the MS, albiet at a slower response speed.

Can anyone verify this? Basically my goal is to do something similar to what the GoodBox was doing, however using the MS-CAN to display information that I pick up from the PCM on the information display.

 

Pretty sure S1s and S2s have very similar if not the same CAN BUS. Only thing is they added more features through the years, such as the advanced keyless entry but the information display and audio units function and look pretty much the same.

Most cars use the instrument cluster as the gateway, but I did some quick looking through the wiring diagrams and it does not seem that the Medium & High Speed CAN networks are shared on the RX-8. I don't see any twisted pair wires coming into the instrument cluster from the Medium Speed CAN. I only see a pair of wires for High Speed on the instrument cluster and you can clearly see the terminating resistor on these two wires in the diagram.

Let's think about what information is actually shared on the Medium Speed CAN. I can only think of vehicle speed, ambient temperature, and cabin temperature. That's pretty much it. Vehicle speed is shared for the Audio system speed controlled volume. Temperature is for the information display and the Auto Climate Control if equipped.

More digging shows that the climate control/temperature information is on a twisted pair, while the vehicle speed is coming from the ABS/DSC module on a single wire. This single wire is then junctioned off to each individual computer that needs vehicle speed information. This is the older ISO system I believe.

So it looks like there is not much information you can get from the Medium Speed CAN. You'll just have to tap into the high speed CAN for the good stuff.

I haven't looked into how the GOODBOX operates, but it sounds like the inventor has already done most of the work.

 

I will have to double check my wiring diagrams when I get home. You are right though, all the stuff I really want is on the HS-CAN, but the lcd display is located on the MS-CAN . I will have to trace those wires to see where they all end up. I can see the one end gets dumped down into the OBD2 port.

I figured the cluster would be the gateway, as it is on most cars, but that is really going to suck since I dont think the cluster has any knowledge of the lcd display.

I actually shot pieter3d a note regarding his GOODbox, and we discussed a bit how different the LCD displays are on the S1 vs S2. We discussed how he didn't think the GOODbox would end up working for the S2. Like I said, I was under the impression that the LCD for the S1 was run under the SPI bus.

I suppose I can set up a single network that talks to both busses, and have my logic keep switching baud rates to get information and send information along each bus.

 

I went and looked at the differences between S1 & S2 audio unit wiring diagrams. (I don't pay much attention to S1 mods since I don't own one, LOL!)


Anyway, it seems they made the information display on the S2 a stand alone unit whereas on an S1, it was an integral part of the audio unit. There is no seperate wiring schematic for the information display on the S1.

Mazda most likely made the swtich to simplify their audio units across the line. It is easier for them to use the same navigation unit or audio unit among all their cars. I believe the CX-7 & CX-9 use the same Navigation units as the one available for the S2 RX-8.

So definitely looks like the GOODBOX won't work as is. You'll need to crack the S2 information display computer looks like.

 

Looks like you were right btw, took a closer look at the wiring diagram



Looks like the instrument cluster is the gateway for the information display which then all goes to the ECU. There must be a way to access all ECU information from the MSCAN then. (which would be amazing)

 

Where did you get that diagram from? Looks totally different from anything I have.

The L/R wire that I see is the "room" fuse circuit according to my diagrams. No information shared on this wire. Just B+ power at all times.

CAN wires are always twisted pair of wires.

 

wow ... lack of sleep ftw, you are right, i was looking at the electrical diagram, and you are correct, they are the room fuse lines

HS-CAN = G/B, L/W
MS-CAN = LG, GY/W

 

http://www.youtube.com/watch?nomobile=1&v=loMnYVDsmWA

An update on what I'm working on. Don't mind the whacky afr reading

 

Nice! looks very promising. keep it up, I'd definitely be interested in something like goodbox for us S2 guys.

 

I am with jrx13, the CAN system is basically the same in S1 and 2's, the console "Information Display" is different by part number though and not interchangeable, but it is sold separately on both Series, no need to purchase any audio gear.

Also is the Main PCM (ECU) are different, mainly because of EMOP set up and a few other changes like the Immobiliser Control Modules are different make/brand.

 

Have you read these sites?

http://blog.hiroaki.jp/can/
http://www.madox.net/blog/projects/mazda-can-bus/

 

refer to https://www.rx8club.com/series-ii-interior-audio-electronics-167/rxduino-development-chat-218257/ on the latest on this topic