Lab 5 – Edge Triggered and SysTick Interrupts

CECS 346 Lab 5 – Edge Triggered and SysTick Interrupts
Preparation:
You will need a TI TM4C LaunchPad.
Book Reading: Textbook Sections 9.4, 9.5, 9.6
Starter Project: CECS346_Lab5_Interrupts
Reference Code: Textbook Program 9.4 (in Lecture 6 slides), TExaSware\C12_EdgeInterrupt,
TExaSware\C10_SysTick
Purpose:
The purpose of this lab is to learn how to use Edge Triggered and SysTick Interrupts, and learn
how to use the Memory and Watch windows in Keil uVision simulator during on-board
debugging.
System Requirements:
• You will write code using “friendly” initialization to initialize 3 different functionalities
such that all 3 functionalities will work regardless of the order the initialization functions
are called. You will code keeping in mind the CECS346 Coding Standards.
• In this lab you will flash the onboard red and blue LEDs. Instead of using a software for
loop to generate 0.1s delay, you will use a SysTick interrupt approach to generate the
same time delay.
• You will create a rising edge interrupt on PF0 and count the number of times it is
triggered in a global variable. (We will use Keil to see the value of the variable.)
Procedure:
1. Download CECS346_Lab5_Interrupts.zip and unzip into Keil\Labware folder. Note there are
5 functions that require being implemented:
a. PortF_LEDInit() - Initialize Port F LEDs
b. SysTick_Init() - Initialize SysTick timer for 0.1s delay with interrupt enabled
c. EdgeCounter_Init() - Initialize edge trigger interrupt for PF0 (SW2) rising edge
d. GPIOPortF_Handler() - Handle GPIO Port F interrupts
e. SysTick_Handler() - Handle SysTick generated interrupts
2. Inplement PortF_LEDInit() to initialize LEDs only (not any switches) using friendly
initialization. See Labware\Lab2_HelloLaunchPad for similar code.
3. Implement SysTick_Init() to initialize a SysTick timer with 0.1 sec delay (assuming the board
is running at 16 MHz) that generates interrupts using friendly initialization. See textbook
Program 9.7 for similar code.
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4. Implement EdgeCounter_Init() to enable edge trigger interrupt for PF0 (SW2) rising edge
using friendly initialization. See textbook Program 9.4 / TExaSware\C12_EdgeInterrupt for
reference.
5. Implement GPIOPortF_Handler() to do whatever is necessary and increment RisingEdges.
See textbook Program 9.4 / TExaSware\C12_EdgeInterrupt for reference.
6. Implement SysTick_Handler() to do whatever is necessary and toggle the red and blue LEDs
at the same time.
7. Compile and simulate it.
8. View the value of RisingEdges in the Watch 1 window. To open Watch 1 window while
debugging, go to View menu -> Watch Windows -> Watch 1.
9. Once Watch 1 is visible, we want to see the value of RisingEdges. Double click on the text
“<Enter expression>” and type “RisingEdges”. The value of RisingEdges should be visible.
10. View the value of RisingEdges in the Memory 1 window. To open the Memory 1 window
while debugging, go to View menu -> Memory Windows -> Memory 1.
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11. Once Memory 1 is visible, type “&RisingEdges” in the Address box. The & represents we
want to see the memory where RisingEdges is stored, not at the value of RisingEdges. (Think
of &RisingEdges as the mailbox, and RisingEdges is what is in the mailbox.) Recall that the
Cortex-M4 processor is little endian, so the first 4 bytes in the top left first row are the little
endian value for RisingEdges.
Deliverable:
1) Demonstrate your lab
a. In simulator – Show RisingEdges incrementing when PF0 (SW2) is released.
b. On board – Show board flashing
2) Submit to the Beachboard Dropbox
a. Software source code (EdgeInterrupt.c)
b. Memory 1 screenshot, Watch 1 screenshot (could be same screenshot)