CAN Frame Frequency

[matt-c]

On my S6 i can set each frame to send over CAN between 1hz and 100hz.

Currently these are set with a few frames on 50hz and others on 5 and 10.

Is there any limitation to increasing the frequency of the frames or is it just based on requirement?

I'm sending CANbus data to RealDash and if i can send it faster my logging will be better.

TY.

[TimH]

In reality, pretty much a "yes, that's OK"

The CANbus is at 1Mbit/s and each frame is comprised of 112 bits, carrying 4 data values (in the case of the Syvecs datastream). That gives us nearly 9000 frames per second, or an absolute maximum of around 36000 parameters per second.

If you have 20 frames defined - that's 80 messages - and set them all to 100Hz, that's only 8000 parameters. But if there're other devices on the bus they will need bandwidth too.

For some parameters, though, there's not much point running them faster than needed (e.g. a 10Hz update-rate GPS, or accelerometer, would be pointless sent at 100Hz).

[stevieturbo]

On my S6 i can set each frame to send over CAN between 1hz and 100hz.

Currently these are set with a few frames on 50hz and others on 5 and 10.

Is there any limitation to increasing the frequency of the frames or is it just based on requirement?

I'm sending CANbus data to RealDash and if i can send it faster my logging will be better.

TY.

Better how ? temperature sensors are very slow.....100Hz would offer no benefit to something that.
Knock sensors would require much higher than 100Hz.

Establish what might benefit from faster and work from there.

[matt-c]

Thanks both for the replies

That's helpful and good to know i can increase the rate if needed.

I was thinking of increasing things like AFR and idle / dbw error to get a better logging for tuning.

[stevieturbo]

Thanks both for the replies

That's helpful and good to know i can increase the rate if needed.

I was thinking of increasing things like AFR and idle / dbw error to get a better logging for tuning.

How fast do you think a typical wideband is ? 100Hz is not necessary.

And DBW control parameters, yes you could log these at a fast rate, but really if you're investigating issues there the fastest place to log them is on the ecu. Although in most cases even 50-100Hz is still plenty.

For most stuff, say around 20Hz is plenty, knock noises etc would require the fastest, but then 100Hz isn't really enough

[matt-c]

I've set most to 50Hz and 6 of the frames at 10Hz.

Maybe a bit overkill on some of the frames, but if there is no downside then it's ok.

[TimH]

Of course, the other factor is whether the receiving device and software can cope with that number of parameters per second, in real time, or if it will discard messages

[matt-c]

Looking at my csv from RealDash it has 50 rows a second, which is the logging rate i've set in RD to match the 50Hz from the S6.

Now why is my bap always 1013 in every log file, seems the initial calculation of it at start up is not working.

[stevieturbo]

unless you have a BAP sensor, it will likely read whatever you have as default value for it, unless you have set it to read atmospheric at key on.

Not hugely relevant in many cases.

[matt-c]

it's set to read key on from the map sensor, but it doesn't work.

Can anyone share working key on settings?

It's an annoyance more than anything, not doing much driving up mountains