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Using MoTeC C125 As A Gateway For A Specialty Use Case

CANBus Communications Decoded

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Hello all,

Great to join this community.

We have a slightly unique use case here. We are developing a specialty camera vehicle for the film and television industry here in the U.S. The vehicle is a four wheel drive, four wheel steering EV with a top speed of around 25mph.

The vehicle will be control-by-wire. Currently, it is set up for an industrial remote but we are migrating the controls over to traditional inputs with a steering wheel and pedals. We are using a steering sensor that speaks on CAN Bus meant for off highway specialty vehicles such as tractors; throttle and brake are from the throttles of a Prius, converted to CAN with an analogue to CAN module. Rest of the controls such as steering mode and speed limiters etc. are going to be controlled with a Blink Marine CAN bus keypad.

This bus set up is well and good, but for a multitude of reasons it is not really possible for us to reprogram the vehicle controller to accept the inputs of these wide ranging, specialised inputs. Currently, the vehicle is set up so that it recives all the control commands with one single CAN message. So we needed a device to act as a gateway to gather all the different data from the steering sensor, throttle, and keypad, and relay that into the structure of the control message for the car.

We were considering using an industrial solution such as the IXXAT CANector, however I came across HPA's video on using the MoTeC as a gateway and thought I should explore the options. It turns out that the MoTeC display has a very extensive control function which I was not expecting, at least judging from the software.

Would love to know if anyone owns a MoTeC C125 and are familar with the limitations of the device. We are looking to use it as a display, and also a gateway to restructure these messages using the "transmit message" function, and using the "alarm" function for error monitoring between the redundent channels of steering and pedal inputs. If anyone has any insight we would greatly appricite it.

Thank you very much,


Hi George,

Another alternative is the L120 enclosed logger, this is the C125 without the screen, so if the screen is not needed then this is a cheaper option. Having said that, for this usage, I would recommend using the C125 so that you have have error messages displayed on the screen, as well as being able to see what is coming in and going out by displaying the channels. Display Creator would enable the creation of custom screens to allow for even greater data display options.

The C12x devices (along with the C18x devices) have been used a CAN bridges on a number of vehicles, I use the C187 in my racecar and do a fair bit of CAN bridging between the four CAN Buses in that Dash. I also modify the signal for some of the channels using the internal functions to reformat the data to suit its usage in other devices. The C12x doesn't have the same level of math available as the C18x displays, but from what you have reported here the C12x should be capable of supporting your requirements.

One limitation that may or may not apply to you is that you cannot have a transmit and receive template with the same base address on the same CAN bus. The software will not allow it. So as an example, if you were receiving messages from a device on 0x300, if you needed to transmit on that address as well, it will have to be set up on the second CAN bus.

Another limitation will be the type of data that you need to transmit and receive, your capped at 32bits (4 byte) for a single message. The dash also doesn't hand. The dash will only handle integers (numbers) and no floating point (equations)

Outside of that, so features have maximum scheduling rates (tables will not be referenced faster than 50hz for instance) but outside of that, the dash offers a high level of flexibility.

Thank you Stephen and Nathan for your help! These are very helpful.

Seems like the C125 does work for our purpose. Looking forward to the build!



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