Laboratory Exercise #2 SpeakerBuzz Solution

1 Introduction




This laboratory implements a new task to generate a dual-tone using the speaker on the LM3S1968 evaluation board. Your GTA will assign additional parts of this exercise.




To begin this lab, make a copy of the Program_Blinky project in your workspace.




Select the Program_Blinky project and right-click.



Select “Copy”



In the workspace pane, right-click and select “Paste”



When asked for a project name, use the project name “Program_SpeakerBuzz”



Within the new project, rename “Program_Blinky.c” to “Program_Speakerbuzz.c” and “Program_Blinky_startup.c” to “Program_Speakerbuzz_startup.c”



1.1 Improve SysTick Coding




Verify the following changes have been made in your “Program_SpeakerBuzz.c” code.




The value of “SysTickFrequency_Nbr” variable should be 10000. This will set the SysTick period to 0.1 milliseconds. Your define statement should look like:



extern uint32_t SysTickFrequency_Nbr = 10000;




1.2 Tone Generation Task




Write a new task with necessary state variables and functions named “Task_Speakerbuzz.c”. Follow the pattern in “Task_Blinky.c”.




Add a call to “Task_Speakerbuzz.c” in your main program.




1.2.1 Initialize GPIO PortH




You must initialize GPIOH bits <1..0 to drive the speaker. Your GTA will give you a frequency for the tone you need to generate and that will determine the SpeakerBuzz delta interval. Here is example set-up code:




//




Enable the GPIO Port H.



 



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SysCtlPeripheralEnable( SYSCTL_PERIPH_GPIOH );




//




Configure GPIO_H to drive the Speaker.



 



GPIOPinTypeGPIOOutput( GPIO_PORTH_BASE,




GPIO_PIN_1 | GPIO_PIN_0 );




GPIOPadConfigSet( GPIO_PORTH_BASE,




GPIO_PIN_1 | GPIO_PIN_0,




GPIO_STRENGTH_2MA, GPIO_PIN_TYPE_STD );




//




Set PortH<0 ON and PortH<1 OFF.



 



GPIOPinWrite( GPIO_PORTH_BASE,




GPIO_PIN_1 | GPIO_PIN_0, 0x01 );




Determine the delta execute time based on the frequency your GTA gave you. Schedule the next execution time equal to the current “SysTickCount_Nbr” value and the delta execute time. Set the state of the task to initialized.




1.2.2 Toggle the Speaker GPIO Bits




When time to execute, you should toggle GPIOH bits <1:0 similar to toggling the LED bit in Task0_Execute() (BlinkExecute()).




Read the GPIOH bits.



Toggle bits <1..0 with an XOR operator



Write the GPIOH bits <1..0 with the new value.



Set a new next execution time.



1.2.3 Laboratory Measurements




Your GTA will ask you to measure the frequency of your “Task_SpeakerBuzz” using an oscilloscope. Make sure you can checkout equipment from the EECS shop.




1.3 Dual-Tone SpeakerBuzz




Write a new task based on your SpeakerBuzz task that alternates between the two tones holding each tone for 750 mS. Your GTA will assign a second tone to implement.































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