Generating Frequencies

Overview

In the previous sections you learned about frequency and period and how to convert between the two. In this lesson you will learn how to use the conversion formulas to generate specific frequencies using your microcontroller and the following steps.

1. Convert frequency to period: The first step in generating a frequency is find the period of this frequency using the conversion formula from the previous section of 1/f = T. Again f stands for frequency and T stands for period. For example:

   1/1382Hz = 0.000723589s
   

2. Divide the period in half: The period of a wave is equal the sum of one high pulse and one low pulse. In your code, you need two delays. One for the length of the high pulse and one for the length of the low pulse. For now we will assume these two delays are always equal.

   0.000723589s/2 = 0.0003617945s
   

3. Convert seconds to us or ms: The next step is creating a delay in either ms or us. You have two options for delay functions. delay() takes values milliseconds. delayMicroseconds() takes values in microseconds. The following is a conversion from seconds to milliseconds.

   0.0003617945s = 0.3617945ms
   

   From the lesson on the delay function we know that it only takes whole numbers, so will need to use the function delayMicroseconds() and now convert the milliseconds tomicroseconds.

   0.3617945ms = 361.7945us
   

   Since the delayMicroseconds() function also only takes whole numbers we will need to round our result.

   361.7945us rounds to 362us.
   

Now we can use the resulting times for the two delays in our loop.

Exercise:

Complete the table below in your notebook. Round your period values to the nearest one millionth. Remember that your delay value is half your period, since you will be using one delay for the high time and one delay for the low time. Round your delay values to the nearest whole number. Write a program to generate each frequency and measure the frequency with your multimeter to confirm. Demonstrate one of these frequencies for your teacher.

Generating Frequencies

Frequency	Period (seconds)	Delay value (us)
345Hz
2876Hz
879Hz
1390Hz

TEACHER CHECK _____