CAN message template creation question

[the_bluester]

OK, I am looking seriously at template creation, and have come across a question that I have not been able to answer with the help file or other reading.

I have a copy of a Haltech CAN message set (the V2 protocol) and was using it to create a new set of comms templates for my own schooling. Some of the messages do not match the available settings in the dash manager comms setup page. For instance there are a number of messages sent at 20Hz which is not a listed rate. For messages falling in between selections do you select the transmit rate below and select "Allow fast receive"? So the 20Hz messages would be 10Hz and fast receive?

[adrian]

For receive messages the drop down box you are talking about doesn't do anything, you can simply leave it to whatever it defaults to and it will make no difference.

When the 'Allow Fast Receive" box is not ticked the dash will sample the channel at 100Hz.

When it is ticked the dash will sample the channel every time it gets a message. How fast this will work depends greatly on how much load the dash is under. Everything up to 500Hz should be fine but above that you may start to miss some messages.

[the_bluester]

Thanks, I will take a suck it and see approach. The dash is not going to be particularly highly loaded.

[adrian]

Just one thing to note, that rate is per message. The dash will work fine with bus loads above 80% with very high CPU loading (above 80% continuously peaking to 100%).

Having a quick look at the Haltech CAN spec it looks like they send around 500 messages a second overall. To put that in perspective our M1's, depending on package, will send anything from 1000 to 2500+ messages a second and the dash reads that with no problems.

2500 messages a second is only about 30% bus load (on a 1Meg bus) so there is still plenty of room for additional CAN messaging.

[the_bluester]

Thanks, I though that would be the case. In my setup there will be the ECU, PDM and keypad on the one bus (Unless I buy any extra goodies) and I expect to have my PDM doing it's share of the work logic wise and spitting out messages for status display and other control on the dash, but the bus loading should be pretty moderate compared to an M1 package.

I will be honest, the only reason I am looking at complicating my life by putting a Haltech ECU in the car is that the budget just wont stretch far enough to put in a MoTec ECU. What I want to do with it just puts an M84 out of contention and I cant quite stretch to an M600 or M1 package.

I don't suppose you guys have a copy of the Haltech CAN protocol that is more up to date than the 2012 document? They are a little coy about releasing it, you would think it was to their advantage to make it harder to integrate their stuff into an existing car rather than the other way around!

[adrian]

I have dash templates that were created from a newer document than 2012. If you send an email to support@motec.com.au I can send them to you.

[the_bluester]

Thanks, I have emailed you on the support address.

[the_bluester]

Got them thanks, they mostly match what I was dong with the 2012 sheet but there are some differences and some they have skipped. I will just have to suck it and see when the time comes and see if the received data makes sense/matches what is reported by the ECU where there are differences.

[adrian]

If you find any errors let me know and I will fix them up.

[the_bluester]

No problem, it will be a while but if I work out any differences I will let you know. Most of the missing ones are pretty low value messages or might have been messages that the sport ECU they appear to have been created for may not have generated.