Greater time resolution using .NET Micro Framework on Netduino board (for dimming an LED)?

Question

I'm programming a Netduino board using the .NET Micro Framework 4.1 and want to get a higher time resolution than milliseconds. This is because I'm attempting to dim an LED by blinking it really fast.

The issue is that the sample code uses Thread.Sleep(..) which takes a number of milliseconds.

Sample code from http://netduino.com/projects/ showing the issue in question:

OutputPort ledOnboard = new OutputPort(Pins.ONBOARD_LED, false);
while (true)
{
    ledOnboard.Write(true);
    Thread.Sleep(1); // << PROBLEM: Can only get as low as 1 millisecond

Even if there's another way to accomplish dimming by not using a greater time resolution, I'm game.

Answer 1

This doesn't answer your question about getting a better time resolution, but it does solve your problem with changing the brightness on an LED. You should be using the PWM module for the Netduino.

Netduino Basics: Using Pulse Width Modulation (PWM) is a great article on how to use it.

Answer 2

I have had a similar problem in the past and used the following method to time in the microsecond range. The first line determines how many ticks are in a millisecond (its been a while since I used this, but I think 1 tick was 10 microseconds). The second line gets the amount of time the system has been on (in ticks). I hope this helps.

public const Int64 ticks_per_millisecond = System.TimeSpan.TicksPerMillisecond;

public static long GetCurrentTimeInTicks()
{
    return Microsoft.SPOT.Hardware.Utility.GetMachineTime().Ticks;
}

Answer 3

You can use a timer to raise an event instead of using sleep.

The Interval property on a timer is a double so you can have less than a millisecond on it.

http://msdn.microsoft.com/en-us/library/0tcs6ww8(v=VS.90).aspx