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Haltech Nexus R5 to HTG GCU

CANBus Communications Decoded

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Good day everyone, Im busy building an E92 M3 race car and I went for the DCT option, I installed the Nexus R5 and all of the systems are functional, the GCU requires quite a bit of data inputs which are configurable over the GCU's CAN inputs. I have made the hard connection to the Haltech using a 4 pin DTM connector, the GCU does not require CAN +12V or GND, since it is a powered device. I have determined CAN H and CAN L on the GCU and connected it to the Haltech accordingly, the Haltech has an option to enable a terminating resistor and the GCU does not have the resistor, do I select the option to turn the resistor on? I need some help setting up CAN broadcasting on the Haltech's side in order for the GCU to receive the data it requires.

Any help will be greatly appreciated.

G'day Dewit. Sounds like a cool project, I've been becoming more and more enamored with the E92s of late.

Are the Nexus and HTG GCU the only devices on the Bus? If so, yes, you need to enable the CAN resistor in the Nexus, and also physically add one at the HGT GCU end. That should sort the hardware side of things.

Now you need to sort the message templates. Can you post up a link to any of the GCU documentation that outlines what it is expecting so receive over CAN?

Unfortunately, I'm not familiar with Haltech NSP (yet, I have a project with it coming up, and will be getting down into the weeds with it), so I'm not sure how configurable it's can output templates are.

In regards to the messaging that the HTG GCU needs to see, it is all laid out on what messages to send on what addresses etc on their wiki guide:


Yeap, that's one half of the puzzle solved. How configurable is the CAN transmission side of a Nexus?

Thanks for all the feedback guys, I received the Haltech CAN protocol from Haltech and setup the Haltech to broadcast the channels I need the GCU to read over CAN 2. I enabled the terminating resistor on the Haltech side, those are the only 2 devices on BUS 2, BUS 1 is used for the display and the 15 button key pad, I am still unsure about the terminating resistor on the GCU side since I just put it on the other side of a 4 pin DTM connector, the BUS is only about 50mm long and not running close to any noisy wiring, is the terminating resistor still necessary on the GCU side? In the mean time I made a new friend in Germany via Facebook, who happened to have a GCU config to read the broadcasted CAN message from the Haltech and was kind enough to share it with me.

Hey Dost by chance would you mind sharing the GCU config file with me ?

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