pwm_songs.c and answered questions. (Canvas)This lab will be due March 8, 2019.
For the Simon midterm project, you’ll need to generate sounds appropriate for button presses, success, and failure. Wire a piezo buzzer to a PWM-capable pin. Your goal is to create a set of functions (i.e., a library) that will allow you to play arbitrary sequences of tones at potentially different speeds. A piezo buzzer produces sounds by transducing electrical fields into motion using a piezoelectric material. They are good for higher frequencies, but not those in the lower part of our hearing spectrum. Begin by experimenting with PWM and the buzzer. Set your PWM carrier frequency to 440 Hz (an “A”).
Now, modify the code you built for question 2 to be general. “Sound strings” should be
specified as a sequence of frequences (or periods) stored in an array, with a separate “tone
length” variable specifying how long each note should be played for. Note that because each
tone has a different frequency, keeping track of how long each has played is a slightly
nontrivial task (though you should be able to figure out a simple way of accumulating periods
properly to account for their different lengths). You should create a function with prototype
void PlaySound(int* SoundString, int StringLength, int ToneDuration) that initializes the
proper global state variables and starts the sound playing. The ISR should ensure that, once
started, the sound string is played once. You might want to create a special tone symbol which
corresponds to a “rest”, to enable more complex sounds.
Create the proper sequences for the first lines of “Twinkle, twinkle little star”, and “Mary had a little lamb”. Set up an infinite loop so that you play a sequence and then have quiet for a few seconds. You may use __delay_cycles for this part of this lab! Be prepared to demonstrate how your code works, including playing the two sequences at different speeds.