Hardware Calibration Switch

[shmed]

I'm working on a little project for my track car, and as part of my plans, I want to replace the hardware calibration switch with an output from an Arduino.

I figured that the hardware switch was just a resistor ladder type arrangement, but having had a little play last night, I'm not so sure.

Can anyone tell me how the switch works please so I can emulate the output from the Arduino?

I am a noob to electronics, so really don't want to tinker too much without being a bit more informed.

Also, if I wanted to power the Syvecs from a bench power supply, can I simply provide power and ground, or will the Syvecs grumble if it can't see any sensors? I have a spare Saab ECU connector, and I want to play with the CAN settings in the comfort of my house.

Cheers

Paul

[shmed]

So, having looked through the manual (RTFM....), I see that the hardware switch actually uses a diode chain. Words I can type, but don't truly understand...

However, reading further, I see that the ECU can be programmed with threshold voltages,which I presume I can find by connecting to the Syvecs. Given these values, I suspect that I can simply 'instruct' the Arduino to output the required voltage and in turn tell the Syvecs to change map.

[stevieturbo]

So, having looked through the manual (RTFM....), I see that the hardware switch actually uses a diode chain. Words I can type, but don't truly understand...

However, reading further, I see that the ECU can be programmed with threshold voltages,which I presume I can find by connecting to the Syvecs. Given these values, I suspect that I can simply 'instruct' the Arduino to output the required voltage and in turn tell the Syvecs to change map.

That's all the BT module and Toucan do when they're used for that purpose.

They simply output a voltage between 0-5v for each Cal setting ( rising from low to high, 1 to 12 )

[TimH]

As Stevie says.

Or get an Arduino CANbus "shield" and do it that way

[shmed]

Hi Tim,

I have an Arduino CANbus shield, but am having issues with it actually reading anything from the Syvecs CAN output.

Have you got any tips at all?

The CAN controller has initialised ok at 1Mbps, but there seems to be nothing to read.

I have it all set up on my test bench with a 'bus' terminated at both ends with 120ohm resistors. I get a 60 ohm resistance across Can-H and CAN-L.

At the minute, I'm I'm barking up a bitrate timing tree as I read something about the CAN bus having to be within a timing tolerance.

I'm trying to obtain the full Syvecs CAN implementation document, but to no avail as yet

Cheers

Paul

[TimH]

There is no CAN implementation document as far as I know. You set it all up in SCal and the parameter scaling is shown there, along with the IDs used.

It's 11 bit ID's, defaulting to 0x600 for the first frame.

Bit timing is usually OK with default settings but I've never used the Arduino shield so don't know about that - I imagine there's loads of example code out there?

Sounds like you've double terminated it though - try removing the termination at the Syvecs end.

[shmed]

Cheers Tim,

Does the Syvecs terminate itself? From what I have read on CAN bus physical specs, the bus should be terminated at both ends with 120 ohm resistors, and you should get 60ohm between H & L (which is what I get).

I'll try removing one of them tonight and see if I see stuff.

There is some Arduino code knocking about, but typically it seems to be that their code 'just works' for them, and when it doesn't work, there's little info about.

I'm down in the weeds of the MCP2515 data sheets now looking at bit timing. I had hoped that once I got the baud (bit) rate right, then I'd be into a whole world of CAN info.

[TimH]

I imagine the S6 has a termination resistor - I never need to add one in for any of the loom adapters nor Toucan at the S6 end. But I don't know this for a fact as CANbus is very tolerant when there are only short cable runs.

[pat]

Gents,

for the record the S6 has got on board CAN bus termination, so that's one end of the bus sorted, it's up to you to terminate the other end

Cheers,

Pat.

[shmed]

Thanks for the replies. So I now have three can Shields for arduino, and can successfully get them taking to each other, but still nothing from the Ecu. Now I have a valid can output to scope, I can see what I'd expect to see in terms of wave form, but with the same parameters set on the scope, I get nothing out of the Ecu.

I've checked continuity between the harness pins and my twisted pair and that is fine. The only thing I can now think (aside from an internal issue) is that the can data is only available when the engine is running (which I find hard to believe).

Is there anything else I might be missing?