Polling rate extremely slow, even with only 3 polled channels - E38 Controller

[aaronc7]

checks out

when the channel list and the chart are not exactly the same which is correct?

thx Keith

My observation....

The channel list shows actual data value updates and displays the last received value. The chart is always interpolating between points. This becomes very apparent when someone is logging way more stuff than they should be. An item in the channel list will might only updated once every second or 2 seconds or whatever, but the chart will show the data always moving-- it's just interpolating between the last and next data point.

I wish VCM scanner gave you a bit more insight into what "buckets" were being used and the expected polling rate or priority. But I also understand this gets really complicated because every ECU is a bit different and this probably gets very complicated from a GUI standpoint.

I'm most familiar with my Gen3 LS and thankfully its pretty simple but I've played with this extensively.

I know Gen3 LS has buckets that are 6 bytes and in a cycle you can poll 4 buckets at a time. Each cycle is around 10hz, so 24 bytes at 10hz.

What I did was set the request logging rate/priority to 10hz for 18 bytes and I set 12 additional bytes to 5hz.

Basically every cycle, the 3 buckets/18 bytes are polled every time and the 4th and 5th bucket alternate cycles, resulting in around 5hz for those.

It was tedious to set up and make it work, but it was important to me to get max possible speed on data that really matters when doing things like VE tuning, etc. That export to csv trick does help shed light on what's really going on too and getting the data rates you want.

Sorry long reply. Just sipping my morning coffee lol.

[abc]

Broadcast is powertrain CAN messages that are just broadcast across the CAN... say engine RPM that, that could be picked up by the ECU/PCM, and the TCM, and the brake module, all at once. Polling is what I described above, the control module sends a request and gets a response and there is some throughout limit. In the screen where you select things to log, it says if its broadcast or polling, and if it's a PID or direct memory logging.

I just poked around a little in the VCM scanner, specifically in the channels list and the chart layout, I don't see where the difference is noted between broadcast and polling parameters. Can you point it out to me? Is it just the symbols on the left side of the channels list?

[Keith@HPTuners]

checks out

when the channel list and the chart are not exactly the same which is correct?

thx Keith

The channels list is designed to be the source of truth. The values you see there are the nearest data point received.

The graphical displays often interpolate between data points to provide a more user friendly picture of what the channel or plot is doing.

[aaronc7]

Yeah exactly, there's also a filter button at the top to see broadcast only.

Not all cars will have any available. For example I also have a 2017 Audi S3 but the powertrain CAN is behind a gateway and isn't available at the OBD port. Only polling options.

[Keith@HPTuners]

Plan of attack is always the same-- gather as much info as possible and try to fix it myself, but if I cannot, then create a ticket or whatever. In this case I think it probably needs to get looked at by HPT, as it's something beyond what I can fix or control.

The comment above about standalone logging is a great one though I think. In my mind that could maybe explain what's going on.... the broadcast parameter could be overwhelming what the processor in the MPVI can handle so as a result the polled parameters suffer. I'm assuming that when using VCM scanner, the dongle is pretty much just a passthru and the PC is doing all the processing-- so that would be a good test. And/or reduce the polling rate of the broadcast parameters, if that's possible.

Your assumptions are correct.

VCM Scanner is significantly more powerful than the MPVIx interfaces, both in processing power but also the scanning engine. The newer MPVIx interfaces can support the more complex scanning engines but are still limited by the micro controller inside them.

[LilSick]

I don't have an answer for you, but one "trick" I've found to help figure out exactly what is going on is exporting to csv and uncheck the interpolation box.

Now you can see exactly what channel is updated when, how often, etc.

how does one do this?

do you export the .hpl file to .csv?

or the channel list itself?

[aaronc7]

Open hpl. Under the door drop down, export I think. You can export as a csv and have the option to enable or disable interpolation. Uncheck it

[LilSick]

thx, yeah that is exactly how to export

now how to figure out the bucket part of it lol