Custom CAN message

[gtihk]

I was talking about a counter at the last byte of a message which keeps changing.
I examined the logged data. It seems to repeat in this order : (3,18,33,48)
The change seems to be at a rate of 100Hz.
I am thinking of replicating this by creating a new variable called "counter".
Then,create a Schedule Function to run it at 100 Hz.

The code within the Schedule Function may be :

if(counter<48)
{
Counter=counter+15;
}
else
{
counter=3.0
}

Will this be a correct way to tackle such a problem? Any comments will be welcome.

[rntechnologies]

Hi gtihk,
Yes, you are correct, that will work okay for a counter of +15.
You can shorten it up a little like this though:
There are some other things to note though; like when you initialise the variable, be careful with the number you initialise with as depending on how you structure things the code may still run after the initialisation and add 15 immediately instead of starting at 3.

Code: Select all

static local <unsigned integer> counter = 49;
if (counter < 48)
{
   counter += 15;
}
else
{
   counter = 3;
}


[gtihk]

I followed the example but there is one error.
It says," the local variable name conflicts with an existing object of the same name.
"All local variables must have a unique name."
I suppose it is referring to the channel created called "counter".
The purpose of the Scheduled Function is to update the channel "counter".
How can this error be avoided?

[rntechnologies]

Because my code has the declaration of the counter variable in it, you have likely already declared this in your own existing code, and as such, you need to remove one of the declarations of the variable 'counter'

[gtihk]

Thanks!
I shall try to fix it.

[gtihk]

Sorted for now.
No more errors.
I added 5 counters in total.

[gtihk]

Next on the to do list would be custom CAN receive such as speeds from the ABS unit.
Any suggestions for this please?

[David Ferguson]

Determine the details of the data you want to receive (ie, bus speed, byte ordering, scaling, messages IDs, etc). You may need to use a CAN bus sniffer / analyzer to figure this information out. Expect to spend many hours on this if you don't have documentation with this information available.

Consider hiring someone to create the code for M1 build for you -- they will need the info above to get started.

If you really, really want to do this yourself, then
Read the M1 Development Manaual section on CAN Communications.
Search this forum for threads on M1 CAN Comunications (there are a couple of receiving CAN data, with some important clues).
Create a scheduled function to read the data and write it into channels that you can use.

Only ask questions about a problem after you have tried to solve it yourself. Please describe what you've done/tried.

Good Luck!

[gtihk]

Thanks, David!
I have used CANcapture and have some information on some vehicles that I have done.
I heard that wheel speed is heavily integrated into different modules and would be a difficult one to solve.
What is your experience on this please?

[rntechnologies]

Is the ABS unit a bosch unit?
If so, Bosch do publish a lot of information surrounding their CAN structure, you should be able to piece together stuff around the internet to help with this.

Another note, Generally the formula to calculate wheel speed should also take into account wheel diameter. So keep that in mind when doing your calculation.