Syvecs Forums

I have some questions regarding the canbus output on the syvecs, basically I am in the middle of writing a raspberry pi application so I can integrate it with the syvecs via canbus.

Can someone help me please?

1 - what is the link speed, this is not the frame frequency but the overarching link speed (carrier)?
2 - does the syvecs act as a master and just stream data or do we have to send any command to get the data?
3 - does the syvecs always stream even if the engine isn't running?


Thanks all

You've Pm.

Well, that did the trick.

Thanks again.

Can I re-raise this question please? I have a similar situation.

Cheers

Paul

Paul,

I can send you the datasheet that I was given, it got me up and running.
If you PM me your email address I'll send it to you.

Regards
Michael.

You have PM

Gents,

In answer to the questions :

1) The link speed when running Custom CAN is 1Mbps. Frames are dispatched every 500uS if they are required - 20 frames, 500uS per frame, yields a maximum individual frame rate of 100 frames per second, for a total of 2000 frames per second. There is plenty spare capacity on the bus at that

2) There are no "masters" on CAN as such, every device has the same priority and the "winner" is the one trying to transmit the lowest ID, it's quite clever really. Note that there is an ACK bit that a transmitter leaves in the recessive state and a receiver is required to drive into the dominant state if it has correctly received the frame (and is interested in it as opposed to just snooping - this way the transmitter knows it succeeded, a bit like signed-for mail). As per description above the ECU will transmit (if required) every 500uS - no prompting is required from any other device and it does not need to make use of the the "remote" features of the CAN spec.

3) The CAN stream is present even if the engine is stopped. It would be nonsense to have to start the engine just to see what the coolant temp was!

Hope this helps,

Pat.

Just rekindling my CAN Bus project, and I am now receiving valid CANBus data, though I don't know how to convert the raw data into the actual values....

I have tried using the conversion formulas shown in sCal, but can't seem to decipher the data.

Can anyone provide any more info about the CAN specification please?

Also, I've noticed that my 'vBat(V)' value seems to fluctuate massively over the received CAN data.

Any help would be greatly appreciated.

Ok, so it seems that a lot of the information I needed was actually out there.... I was misinterpreting my data thinking the CAN was outputting the DLC value followed by the data value, when in fact I should be summing the two bytes into a single value.....

Would still be useful to get a 'paper' copy of the RAW stream conversions if possible please?

I seem to recall the conversion table for vBat was y = (x/1000)+0, but with my (now summed) values, I get values ranging from 216 to 222, which gives me a voltage of 0.216 to 0.222.

If I use the formula y = (x/100)+10 then I get a reasonable figure, but I'm fairly sure you can't just make up your own conversions....

God,I'm such a bell end. Put the hex numbers together and I get the right value...