Vary timer period programmatically

[JojoS (Johannes Stratmann)]

I had started a thread about callback performance here and I’ve just added a link to may sources:

Callback runtime

Hello, I have written a stepper motor driver that uses a variable hardware timer period for generating step pulses. The hardware timer uses a CThunk to call a classes method from the the timer ISR. then this method is calling a callback for the user function of the timer component. These two callbacks take about 4 µs runtime on my STM32F407 @ 168 MHz. This seems to be a lot, the calculation of the period time with several floating point operations take less than 2 µs. Are callbacks so expens…

If you’re using a STM32 MCU, then the HWTimer class may work for you. It isn’t heavily tested, I’ve used it with F407 and F411.
You want to use it also for a stepper driver, there the overhead of the Mbed Timer is significant. I will improve it further, also the CThunk costs a lot of cycles.
My StepperController has some fixed settings and needs also some more work. But acceleration and deceleration works fine, I have used the ramp function from the Arduino AccelStepper Lib. The calculation is using float math, so a MCU with FPU should be used.