9 years, 10 months ago.

3 tickers should be fine, I don't know how many the mbeds can handle, but I have used 8 before( all around 440hz) on the mbedLPC1768. If you want to use less, setup the fastest ticker you need, and use a counter to divide it down for the slower rates. Just remember that everything will need to be done before the next tick comes in and you may have to do all operations in one interrupt.

9 years, 10 months ago.

I personaly would recommend 1 ticker. driving a schedule.

So evey other tick. You do your fastest test. then the other interleaved ticks you spread out the other tasks

some of which can be processing data. Creating a CSV file saving to SD.

Then use XCEL to do the graph etc

note ther will be ticks that do nothing and some that might need 2 or more ticks

ceri

9 years, 10 months ago.

If possible avoid writing to the log file in a ticker or any other interrupt. Capture the data on a ticker/interrupt and put it into a buffer.

In your main function have a while (1) {...} loop that checks if there is data waiting in the buffer and if there is writes it to the log file.

Remember to declare the counter used to indicate that there is data in the buffer as being volatile. Without it the main loop may not pick up value changes made by an interrupt.

9 years, 10 months ago.

Tickers are pretty light-weight. Why not just use one per sample rate, and just sleep in the main loop?

As for the pulse trains, you'd be better off using the built-in timer hardware to count them. Just use a timer input pin for each of the pulse trains, and read the timers' counter in your 5Hz interrupt handler.

TIM3 is used for the microsecond timer.

9 years, 10 months ago.

I have one working with a main loop running at 10 Hz where i process the data serially polled from ECU send over bluetooth and write down to usb. ADC conversions for temp, pressure and accelerometer are done in tickers at their rates.

Badly coded years ago as my first project, but still working strong.

9 years, 10 months ago.

The following method of scheduling works very good for my program which involves critical functions. Note: I do not use the printf-function on this. I only use putc and take care that my buffer is not filled up. Modserial provides neat functions to check how much of the buffer is used. I have experienced "blocking" or something like that if I try to send or store too much data.

http://mbed.org/users/AjK/code/MODSERIAL/

#define     SLOW    1
#define     MEDIUM  10
#define     FAST    400

Ticker      SlowTick,
            MediumTick,
            FastTick;

bool TickSlowVar, TickMediumVar, TickFastVar;
int main()
{
    SlowTick.attach_us(&SlowTickFunction, 1000000/SLOWFREQ);
    MediumTick.attach_us(&MediumTickFunction, 1000000/SLOWFREQ);
    FastTick.attach_us(&FastTickFunction, 1000000/FASTFREQ);
    while(1){
        if(TickFastVar==1){
            TickFastVar=0;
            //run 400Hz code here
        }
        if(TickMediumVar==1){
            TickMediumVar=0;
            //run 10Hz code here
        }
        if(TickSlowVar==1){
            TickSlowVar=0;
            //run 1Hz code here
        }
    }


void SlowTickFunction()
{
    TickSlowVar=1;
}

void MediumTickFunction()
{
    TickMediumVar=1;
}

void FastTickFunction()
{
    if(TickFastVar==1){
        //Ticker called again before the tick was "used" and code was able to run.. Report/do something/debug code.
    }
    TickFastVar=1;
}