Andy's Workshop Forums

As I write more and more stm32plus code I thought it might help people if I share small snippets of code to do common tasks in the spirit of the github gist. Feel free to contribute snippets yourself and/or comment on others.

I needed to generate a high frequency 50/50 PWM signal out of PA2 on the F0. The device I was working with was fairly flexible on the exact frequency so I chose 12MHz because it's an exact division of the 48MHz core clock which means that a precise frequency will be generated. PA2 is the TIM2 channel 3 output. Here's how I did it:


Timer2<
        Timer2InternalClockFeature,
        TimerChannel3Feature<>,
        Timer2GpioFeature<
          TIMER_REMAP_NONE,
          TIM2_CH3_OUT
        >
      > clk;

  clk.setTimeBaseByFrequency(24000000,1);
  clk.initCompareForPwmOutput();
  clk.enablePeripheral();
  clk.setDutyCycle(50);


The timer is set to tick at 24MHz with a very low reload count of 1 so it will toggle every tick giving a frequency of 12MHz. Adjusting the frequency will get you different frequencies. For example, 48000000 will get you the maximum frequency of 24MHz and 12000000 gets you 6MHz.

A request came in to the github issues tracker (https://github.com/andysworkshop/stm32plus/issues/133) asking for an iterator feature for GPIO pins that could function like an STL iterator (http://www.cplusplus.com/reference/iterator/) and therefore take advantage of the utilities provided in the <algorithm> (http://www.cplusplus.com/reference/algorithm/) header.

I've now added this feature (https://github.com/andysworkshop/stm32plus/blob/master/lib/include/gpio/GpioIterator.h) to the master branch to be released with version 4.0.3. You will need to include <algorithm> for most of the STL algorithms and "util/StdExt.h" for the algorithms that I've imported from the C++11 release of the STL (all_of (http://www.cplusplus.com/reference/algorithm/all_of/), any_of (http://www.cplusplus.com/reference/algorithm/any_of/), none_of (http://www.cplusplus.com/reference/algorithm/none_of/), find_if_not (http://www.cplusplus.com/reference/algorithm/find_if_not/)).

Here's some examples of possible usage:

Set all pins high in a group using just the iterator:


GpioC<DefaultDigitalOutputFeature<1,7,9,12,14>> pc;

for(auto it=pc.begin();it!=pc.end();it++) {
  it->set();
}


Set all pins high in a group using a C++11 lambda:


GpioC<DefaultDigitalOutputFeature<1,7,9,12,14>> pc;

std::for_each(pc.begin(),pc.end(),[](GpioPinRef &g) { g.set(); });


Check if all pins are high in a group using a C++11 lambda:


GpioC<DefaultDigitalInputFeature<0,1,2,7,12>> pc;

if(std::all_of(pc.begin(),pc.end(),[](GpioPinRef& g){ return g.read(); }) ) {
  // all pins are high
}


In a configuration where some port pins are output and some are input, do something if at least one of the input pins is set:


GpioC<DefaultDigitalInputFeature<1,7>,DefaultDigitalOutputFeature<8,9>> pc;

if(std::any_of(pc.begin(),pc.end(),[](GpioPinRef& g){ return g.getMode()==Gpio::INPUT && g.read(); }) ) {
  // at least one pin is set
}