G120 Hardware PWM Example

NETMF & Gadgeteer
1

Looking for the method to do hardware PWM…to be exact i want to control the brightness of the LCD backlight…mmm…might be an overkill?

Can PWN pins have different frequencies?

2

SignalGenerator is great for that purpose and work on any pin, not just PWM.

3

Is this a namespace that i need to use? But is it hardware or software pwm?

4

Many MCUs have a feature called Output Compare.

In fact the SignalGenerator class in 4.2 used to be OutputCompare class in 4.1

https://www.ghielectronics.com/downloads/man/Library_Documentation_v4.2/Premium/Index.html

It is a Premium feature, although @ taylorza has implemented it for Hydra as well.

5

This is how you will control brightness for example


        using  GHI.Premium.Hardware;
        
        ...
        private SignalGenerator backLight;

        ...
        backLight = new SignalGenerator(backLightPin, true, 2);
        ...

        public void SetBrightness(int percentage)
        {
            if (percentage < 0 || percentage > 100) 
                throw new ArgumentException(); 
            if (percentage == 0) 
                backLight.Set(false); 
            else if (percentage == 100) 
                backLight.Set(true); 
            else 
            { 
                const int PERIOD = 10000; 
                int highTime = PERIOD * percentage / 100; 
                backLight.Set(true, new uint[2] { (uint)highTime, (uint)(PERIOD - highTime) }, 0, 2, true); 
            }
        }
6

I just use the PWM class

static PWM brightness = new PWM(Cpu.PWMChannel.PWM_6, 2000, 1900, PWM.ScaleFactor.Nanoseconds, false);

brightness.Start();

This works for me on the G120HDR.

1 Like
7

I have connected a passive buzzer to pwm6…i have noticed that it on be default. Can this be changed?

static PWM brightness = new PWM(Cpu.PWMChannel.PWM_6, 2000, 1900, PWM.ScaleFactor.Nanoseconds, false);

brightness.Start();
8

All pins are pulled high by default. Add a pull down resistor.

9

Thanks Gus…problem solved