Feeler: Open Source OBC Firmware

[m2pc]

So if the OBD-I bus is 2-wire, why does NavCoder apparently work using the "simple interface" which has only 1 wire? I'm a bit confused.

[johnf]

Later modules only need the one wire, TXD.

[m2pc]

Later modules only need the one wire, TXD.

By "later" do you mean 96+ (OBD-II)? If possible, I'd like to make the openOBC compatible with the complete 3 series from OBD-I thru OBD-II.

[Joylove]

So if the OBD-I bus is 2-wire, why does NavCoder apparently work using the "simple interface" which has only 1 wire? I'm a bit confused.

It's designed for iBus cars, E46, E39, X5. Those modules are fully OBD2, and the iBus is an OBD2 packet with a source prefix, to identify the sender.

By "later" do you mean 96+ (OBD-II)? If possible, I'd like to make the openOBC compatible with the complete 3 series from OBD-I thru OBD-II.

You'd need to run an OBD2 wire from the engine bay to the OBC then. They are two different and independant data busses, OBD2 only connects to two modules, and is only enabled in US market E36.

OBD1 and OBD2 can both can carry the same payload, but packaged in differnet message structures. You would gain no additional functionality.

[m2pc]

It's designed for iBus cars, E46, E39, X5. Those modules are fully OBD2, and the iBus is an OBD2 packet with a source prefix, to identify the sender.



You'd need to run an OBD2 wire from the engine bay to the OBC then. They are two different and independant data busses, OBD2 only connects to two modules, and is only enabled in US market E36.

OBD1 and OBD2 can both can carry the same payload, but packaged in differnet message structures. You would gain no additional functionality.

What I meant is I want to use the most compatible interface. I'm all for the ADS/D-Bus interface if it's present in all years of the E36.

What's got me scratching my head is that Jochen said someone got their E36 DME to respond using the NavCoder software.
I'm merely trying to replicate that on my own to better understand the bus system.

The plan is to get familiar with it using an existing, proven interface (NavCoder, or maybe even CarSoft) then implement a subset of those functions directly in the openOBC itself.

I'll go back and read Benemorious' posts earlier in this thread to see how exactly he was getting data out of the DME. He did mention the whole "5 baud/10.4k baud" scenario, so he may have been talking over the OBD-II bus, not the D-Bus.

My goal is full D-bus support.

[Joylove]

What I meant is I want to use the most compatible interface. I'm all for the ADS/D-Bus interface if it's present in all years of the E36.

What's got me scratching my head is that Jochen said someone got their E36 DME to respond using the NavCoder software.
I'm merely trying to replicate that on my own to better understand the bus system.

The plan is to get familiar with it using an existing, proven interface (NavCoder, or maybe even CarSoft) then implement a subset of those functions directly in the openOBC itself.

I'll go back and read Benemorious' posts earlier in this thread to see how exactly he was getting data out of the DME. He did mention the whole "5 baud/10.4k baud" scenario, so he may have been talking over the OBD-II bus, not the D-Bus.

My goal is full D-bus support.

Yes, Jochen was getting emailed data logs from a car with OBD1 support from the DME. From what I understood was taking the OBD1 messages and learning about the message structure.

He then added that knowledge of DS2 to Navcoder. I think.

[m2pc]

Ok, so I just built another "simple interface" just in case my first one was bad... Tried connecting it to X16/Pin11 of the ZKE and still no data. When I connected an oscilloscope to the simple interface, I can see that the bus idles high (+12V) and then pulls low for data. I see the data being sent from NavCoder on the scope but no reply from the cluster.

Do I need a stronger pullup on the TXD line? I noticed the vehicle has 820Ohms, whereas I'm using 10K Ohms.

I think this cluster is from the earlier (pre-1996) E36s... I wonder if I need to pull the RXD line one way or another to "wake up" the ZKE?

Any ideas?

[Joylove]

If you check the PDF I posted, the RxD is connected to the Rx line on the RS232.

You gotta remember this system was designed for E34 or E36. Think ~1986 communications.

I think you talk on RxD and listen on TxD.

[Joylove]

DP: I bet if you monitor RxD and TxD on a live car, you'll see chatter between the modules. You should be able to see requests and responses for data. You may even be able to trigger requests with things like the OBC and BC stalk switch.

[m2pc]

If you check the PDF I posted, the RxD is connected to the Rx line on the RS232.

You gotta remember this system was designed for E34 or E36. Think ~1986 communications.

I think you talk on RxD and listen on TxD.

Hmm, I checked the E36 Electrical Troubleshooting Guide and apparently RXD and TXD are linked together by a jumper in the round diagnostic connector when the cap is installed (see attached).

[Joylove]

Yes the lines are shorted on OBD2 cars at least when the cap is fitted so that the 16 pin plug has access to the L line. Dunno about the E36. I don't know if the DS2 bus is idle when the car is not connected to a tester. Only a scope can tell.

One way to progress would be to get INPA working over DS2. You are going to need it to sniff packets for the various sensors anyway, so it is a good way to learn about getting your interface going. The ADS_DOKU when run through a translator may tell you what you need to know about how the DS2 bus works.

Check my guide here for the software side.

[m2pc]

Ok, so I stuck an oscilloscope on the TXD and RXD lines separately yesterday. Put the key in the ignition, started the car, and nothing showed up on the bus lines behind the OBC.

So, it appears that the D-bus is only 'active' once woken up by something like INPA. I'm going to install that and see if I can get it working. Another approach I may take is to plug in my Peake reader and intercept its packets, assuming it's talking over the D-bus.

As a side note, just for kicks I reverse engineered the D-bus interface on the OEM OBC. Here's the circuit (D_BUS = X1071/Pin 5):


More to follow once I get something talking!

[Joylove]

Now I'm totally confused. WTF does RxD X1071.7 do then?

I assumed DS2 was little more than level shifted RS232, having looked at some of the diagrams.

Having looked again, maybe not.
Unmod:

Modified:

[m2pc]

Now I'm totally confused. WTF does RxD X1071.7 do then?

I assumed DS2 was little more than level shifted RS232, having looked at some of the diagrams.

Having looked again, maybe not.
Unmod:

Modified:

JoyLove,

I started tracing that pin (X1071/7) and it goes all over the place to a bunch of resistor dividers and diodes. I'll trace it fully and see what it looks like. I'm thinking maybe this was used to "wake up" the OBC for older E36's?

I'm hoping I can hop on the D-bus from the OBC itself instead of having to tap into the round connector under the hood. Normally the OBC uses these data lines for coding from an external source, but I'm hoping I can use them in 'reverse' and access the other modules in the car.

Yes, your schematic takes the RS232 signals into the LIN transceiver, where they come out as a single line.

Does that schematic work with INPA?

[Joylove]

Allegedly the second one works.

The way I understood these busses are OBD1, DS2 via ADS was how the car was designed, it was all proprietry and BMW were all happy Germans. They were forced in 1996 to support OBD2 for Emissions via DME and EGS in the US. They begrudgingly did so, but did not remove the OBD1 from 1996-1999, merely bolted on a supplementary bus to support a small subset of commands to remain legal. And in the EU, that code was never enabled, such was their unwillingness to allow non-BMW garages to have access to the diagnostics.

[Joylove]

...

[m2pc]

Ok, so good news from my end! I got INPA working with the ebay connector!

I have the following

1) Mac OSX
2) VMWare running WinXP PRo
3) USB to serial adaptor (cheap one!)
4) Cheap eBay EDIABAS OBD connector w/round 20 pin adaptor

I followed JoyLove's INPA install guide except that I chose US instead of UK, and my DME version was 41.1.x not 42.x.x IIRC
After that it worked and I could see the ID info, year and month of production, and a bunch of status info like engine RPM, coolant temp, and more!

I plan to see which pins INPA is using and also see if I can get it working with a handmade interface, then I plan to sniff the data packets to emulate the functions on my own.

Also, I got a PM from one of the formerly active members in this thread, Benemorious, who will be back to help me out hopefully, or at least answer bus-related questions!

[Joylove]

Good news!

I plan to see which pins INPA is using

+1. You may be talking OBD2. Are the ZKE and KOMBI available? If so you are talking DS2.

I would be interested in the mods you used to get USB-serial with DS2 going. That would be a first, everyone else needs the DSR.

Did you select STD:OBD or STD:ADS in the installation?

[m2pc]

Good news!+1. You may be talking OBD2. Are the ZKE and KOMBI available? If so you are talking DS2.

I would be interested in the mods you used to get USB-serial with DS2 going. That would be a first, everyone else needs the DSR.

Did you select STD:OBD or STD:ADS in the installation?

I played with INPA further this morning and found the ZKE and KOMBI aren't responding... so this must be using the OBD-II interface. I did manage to accidentally reset the adaptation (is this bad?)
I selected STD:OBD during installation, like your guide stated.

I do see mention of DSR in my USB serial HW properties page in Windows XP (see attached). I wonder if my eBay adaptor has the wrong pins connected?

[Joylove]

Reset adaptations: Don't do it while the engine is running. Expect high and lumpy idle for 100 miles while the engine re-learns its adaptations.

What is the USB-RS232 chip you are using? Prolific PL2303?

Yes you are probably talking over OBD2, and OBD1 DS2 isn't supported. Are there OBD1 commands appearing on the OBD1 bus? there could be a OBD2->OBD1->OBD2 translator (bridge) running. In the E46, there is an OBD2->iBus->OBD2 bridge running all the time, for example.

[m2pc]

Reset adaptations: Don't do it while the engine is running. Expect high and lumpy idle for 100 miles while the engine re-learns its adaptations.

What is the USB-RS232 chip you are using? Prolific PL2303?

Yes you are probably talking over OBD2, and OBD1 DS2 isn't supported. Are there OBD1 commands appearing on the OBD1 bus? there could be a OBD2->OBD1->OBD2 translator (bridge) running. In the E46, there is an OBD2->iBus->OBD2 bridge running all the time, for example.

I'm using a cheap USB cable with RS232 and Parallel on the same head. It uses a Moschip MCS7715 controller: http://www.moschip.com/mcs7715.php

I should stick a scope on the OBD-I TXD line and look for traffic while using INPA.

I just purchased one of these to try next: http://cgi.ebay.com/BMW-specific-KKL...#ht_500wt_1156

They apparently did the battery detect mod and the pin 7&8 jumper mod already.

[Joylove]

Another option is this.

http://cgi.ebay.com/ebaymotors/BMW-I...motiveQ5fTools

[benemorius]

Hi all! Looks like I have quite a few pages to catch up on. I'm still reading but from scanning through the pictures it looks like there's some mbed and arduino action, as well as another hacker or two joining in the fun. Very exciting! I look forward to getting my hands dirty again, life permitting.

[m2pc]

Hi all! Looks like I have quite a few pages to catch up on. I'm still reading but from scanning through the pictures it looks like there's some mbed and arduino action, as well as another hacker or two joining in the fun. Very exciting! I look forward to getting my hands dirty again, life permitting.

Welcome back!

[benemorius]

Welcome back!

Thanks! I think you should be able to talk to all your modules with any OBD ediabas adapter and INPA in OBD mode as your e36 is 96+. You might try shorting the txd and rxd lines together. Your adapter may only be transmitting on txd and any module listening on rxd wouldn't hear it. As I recall, this doesn't impair communications in OBD mode. And certainly it can cause no physical harm. The names txd and rxd are misleading as full duplex communication is implied. This is not how I observe it to function though in any case at any time. Almost all communication (no matter which module) occurs bidirectionally on txd. The only thing I ever see happen on rxd is the first packet going out from INPA for the "older" modules we're always talking about. As I recall, I thought that was only the DME on my 94 e36. Perhaps it was my OBC too. I guess I never talked to it since I always hook up INPA through the OBC connector.