1. ECE 3567 Microcontroller Lab
Laboratory Background
and
Project #1
Autumn 2018 Dr. Gregg Chapman

2. Module 1: The C Programming Language

3. Switch Statements

4. If-else Statements

5. While loops int main() { Initialize(); while (1) Do_Stuff();
Do_More_Stuff(); }
return 0;

6. For loops

7. Functions Called by Value

8. Functions Called by Reference

9. Function Prototypes void funct1(); void funct1(void);
void funct2(unsigned int);
unsigned int funct3(void);
unsigned int funct4(char);
unsigned int funct5(char, unsigned int);

10. Function with Local Variables

11. Data Types (Processor Dependent)
MSP430 Series Microcontrollers

12. Data Types C Programming Language

13. Compiler Directives
#include
#define
#pragma
#ifdef
#ifndef
#typedef

14. #include
#include – A compiler directive that adds the contents of an external file to the current file definition.
#include “stdio.h” // has to be between quotes
#include “3567.h”

15. #define
#define – Declares a constant and may or may not give it a value. Can also be used to label a macro.
#define RED 0x11

16. #pragma
#pragma – Tells the compiler to include something once if it is included in multiple files.

17. #ifdef / #ifndef
#ifdef – Conditional compilation based on a definition
#endif
#ifndef – If this hasn’t already been defined
#define __MSP_HAS_AES256__ #ifdef __MSP430_HAS_AES256__ conditional code goes here #endif // __MSP430_HAS_AES256__

18. Data Types #typedef
#typedef – Defines an alias name or a new type The typedefs for abbreviated variable types are defined in stdint.h
typedef signed char int8_t;
typedef unsigned char uint8_t;
typedef int int16_t;
typedef unsigned int uint16_t;
typedef long int32_t;
typedef unsigned long uint32_t;
typedef long int64_t;
typedef unsigned long uint64_t;
const uint16_t BaseAddress; // Base Address of EUSCI_A port
const uint8_t TxPort;// GPIO Port settings for TX pin

19. Variable Declaration Modifiers
const
volatile
extern
static
extern volatile unsigned int temp;

20. volatile
The variable scope is available to all functions and all files in the project
The variable can be changed anywhere in the project

21. const
The variable will have a single value at runtime and cannot be changed in the program

22. static
The variable can be used by multiple C functions within a single .c file, but not across files.
Holds the last value assigned to it when the process is acting outside of the processes defined in the file.
static int x;
function() {
int y;
y = y+1;
x = y; }
function2() {
x = 2*x -1; }

23. extern
The variable can be used in the current file, but is declared in another file

24. Local Variables Declared inside functions
Are not preserved when the execution returns form the function
void delay_cycles(unsigned int x) {
unsigned int a;
a = x;
while (a >= 0)
a--; }
return;

25. Constant Declarations
There are “constant” variables:
const int x = 0x1234;
Constant numbers are usually defined with a the compiler directive:
#define RED 0x11

26. Global Variables
Global variables are defined BEFORE a function and may be volatile, static, extern, etc.

27. Module 2: NUMBERS and REGISTERS

28. The Hexadecimal Number System.

29. Registers
Each 4-bit nibble can be converted to a single Hexadecimal character.
Register contents are almost always expressed in hexadecimal values.

30. Registers – Bit numbering
WE USE:

31. Hexadecimal Values of Bit Positions1
0x08
0x04
0x02
0x01
0x10
0x20
0x40
0x80

32. Hexadecimal Values of Bit Positions1
0x0F
0xC7
0x03
0xC0
0xF0
0x00
0x55
0xAA
0xFF

33. Registers
0xE , or Eh
0x0 , or 0h
0x0 , or 0h
0x4 , or 4h
Each 4-bit nibble can be converted to a single Hexadecimal character. The register value shown is: x04E0

34. HOW TO SET A BIT IN A REGISTER
In C programming, the | character is a BITWISE OR
NOTE THAT: 0 | 0 = 0
0 | 1 = 1
1 | 0 = 1
1 | 1 = 1
By BITWISE ORing a register with 1s in the bits you want to SET, and 0s in the bits that you want to preserve, YOU ONLY SET THE BITS AT LOCATIONS THAT THERE ARE A ONE

35. HOW TO SET A BIT IN A REGISTER EXAMPLE 1:
RESIGTER is: SET Bit 4
REGISTER |= 0x10; 0x10 =
( ) | ( ) = ( )

36. HOW TO SET A BIT IN A REGISTER EXAMPLE 2:
RESIGTER is: SET Bit 2
REGISTER |= 0x04; 0x04 =
( ) | ( ) = ( )

37. HOW TO SET A BIT IN A REGISTER EXAMPLE 3:
RESIGTER is: ???? ???? SET Bit 7
REGISTER |= 0x80; 0x80 =
(???? ????) | ( ) = (1??? ????)
You have insured that Bit 7 is SET

38. HOW TO SET A BIT IN A REGISTER EXAMPLE 4:
RESIGTER is: SET Bits 0 and 1
REGISTER |= 0x03; 0x03 =
( ) | ( ) = ( )
You have SET bits 0 and 1.

39. HOW TO CLEAR A BIT IN A REGISTER
In C programming, the & character is a BITWISE AND
NOTE THAT: 0 & 1 = 0
1 & 1 = 1
By BITWISE ANDing a register with 1s in the bits you want to preserve, and 0s in the bits that you want to clear, YOU ONLY CLEAR THE BITS AT LOCATIONS THAT THERE ARE A ZERO

40. HOW TO CLEAR A BIT IN A REGISTER EXAMPLE 1:
RESIGTER is: Clear Bit 4
REGISTER &= 0xEF; 0xEF =
( ) & ( ) = ( )

41. HOW TO CLEAR A BIT IN A REGISTER EXAMPLE 2:
RESIGTER is: Clear Bit 3
REGISTER &= 0xF7; 0xF7 =
( ) & ( ) = ( )

42. HOW TO CLEAR A BIT IN A REGISTER EXAMPLE 3:
RESIGTER is: Clear Bit 0
REGISTER &= 0xFE; 0xFE =
( ) & ( ) = ( )
You have insured that Bit 0 is cleared

43. HOW TO CLEAR A BIT IN A REGISTER EXAMPLE 4:
RESIGTER is: ???? ???? Clear Bit 7
REGISTER &= 0x7F; 0x7F =
(???? ????) & ( ) = (0??? ????)
You have insured that bit 7 is cleared

44. HOW TO CLEAR A BIT IN A REGISTER EXAMPLE 5:
RESIGTER is: Clear Bits 6 and 5
REGISTER &= 0x9F; 0x9F =
( ) & ( ) = ( )
You have cleared bits 6 and 7

45. Other Ways to Express the Bit Patterns
= 0x08 = BIT3
= 0xF7 = ~0x08 = ~BIT3
Because a #included header file msp430fr6989.h contains: This is HEX not Binary
#define BIT (0x0001)
#define BIT (0x0002)
#define BIT (0x0004)
#define BIT (0x0008)
#define BIT (0x0010)
#define BIT (0x0020)
#define BIT (0x0040)
#define BIT (0x0080)
#define BIT (0x0100)
#define BIT (0x0200)
#define BITA (0x0400)
#define BITB (0x0800)
#define BITC (0x1000)
#define BITD (0x2000)
#define BITE (0x4000)
#define BITF (0x8000)

46. TI Method of Setting BIT Fields – On Quiz
DEFINES THE FIRST BIT OF THE FIELD TO BE USED
2*0x1000u
#define BIT (0x0001)
#define BIT (0x0002)
#define BIT (0x0004)
#define BIT (0x0008)
#define BIT (0x0010)
#define BIT (0x0020)
#define BIT (0x0040)
#define BIT (0x0080)
#define BIT (0x0100)
#define BIT (0x0200)
#define BIT (0x0400)
#define BIT (0x0800)
#define BIT (0x1000)
#define BIT (0x2000)
#define BIT (0x4000)
#define BIT (0x8000)
STEPS:
1. Convert this number to BINARY
2. Place the number in the register with the Least Significant Bit defined by this value (See Table)
9*0x0020u:
7*0x2000u:
3*0x0040u:

47. HOW TO CLEAR A BIT IN A REGISTER EXAMPLE 6:
RESIGTER is: Clear Bits 6 and 5
REGISTER &= ~(BIT6 + BIT5); (BIT6 & BIT5) = ( ) + ( ) =
~(BIT6 and BIT5) =
( ) & ( ) = ( )
You have cleared bits 6 and 7

48. Module 3: The MSP430FR6989 Microcontroller

49. The MSP430FR6989 Microcontroller - Overview

51. I/O Port Registers Input Registers (PxIN) Output Registers (PxOUT)
Direction Registers (PxDIR)
Pullup or Pulldown Resistor Enable Registers (PxREN)
Function Select Registers (PxSEL0, PxSEL1)
Interrupt Settings (PxIFG, PxIES, PxIE) NOTE: x – substitute the number of the PORT

52. I/O Ports – Multi-purpose Pins
Primary
Secondary
Tertiary

53. I/O Ports
I/O
Primary
Secondary
Tertiary

54. I/O Ports Port Number and Bit Number TI Conventions
This is the number of the BIT in the PORT
This is the number of the PORT
P Bit 6 of Port3

55. I/O Ports

56. I/O Ports

57. I/O Ports

58. I/O Ports

59. I/O Ports

60. I/O Ports

61. I/O Ports
(and possibly P3 and P4)

62. I/O Ports – Putting It All Together
Suppose that you wanted to configure BIT 2 of PORT 2 as a Timer B0.4 output for a PWM application
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0 X
OUT 1
P2SEL0
P2SEL1
P2DIR
P2OUT
P2REN

63. Control Registers
Every MODULE in a Microcontroller has one or more CONTROL REGISTERS to configure the functions of the module.
Each CONTROL REGISTER is divided into FIELDS
Each FIELD sets one PARAMETER of the MODULE to a specific function
The number of options for the PARAMETER determines the number of BITS in the FIELD
Each BIT has a Power-up DEFAULT value

64. The Timers
There are FIVE 16-bit Timer Modules in the MSP430FR6989 Microcontroller
TB0
Has 7 Capture/Compare Registers
TA0
Has 3 Capture/Compare Registers
TA1
TA2
Has 2 Capture/Compare Registers (internal only)
TA3
Has 5 Capture/Compare Registers (internal only)

65. Timer Hierarchy CAPTURE or COMPARE Modes Capture Compare
TIMER Counting Modes
Stop Up
Continuous
Up/Down
OUTPUT Modes
Output
Set
Toggle/Reset
Set/Reset
Toggle
Reset
Toggle/Set
Reset/Set
Pulse Width Modulation

66. CAPTURE Mode

67. COMPARE Mode

68. TIMER Modes
There FOUR Timer MODES: This describes what the COUNTER is doing (TAxR or TB0R)
STOP Mode
UP Mode
Continuous Mode
UP/DOWN Mode

69. UP Mode

70. Continuous Mode

71. Up/Down Mode

72. UP Mode

73. OUTPUT Modes There EIGHT OUTPUT MODES:
This describes what the OUTPUT SIGNAL is doing (OUT1 – OUT6 on TBO e.g.)
Compare Registers are used to SET or CLEAR the OUTPUT signal

74. OUTPUT Modes
There EIGHT OUTPUT MODES:

75. Output Examples
“Pulse Width Modulation”

76. Interrupt Service Routines
Require a #pragma vector= NAME_OF_VECTOR
There is USUALLY an unused_interrupt file with all of the #pragmas for all possible interrupts. The vector you wish to use must be commented out in the unused_interrupt source file.
ISR must be preceded by the reserved for implementation name of : __interrupt

77. Clock Modules
Four Internal Clocks (Can be linked to CLK sources and adjusted) Typical Values
MCLK Master Clocks
SMCLK Subsystem Master Clock
MODCLK Module Clock
ACLK Auxiliary Clock KHz
Two External Clock Sources
LFXTCLK (Low Frequency XTALS) KHz
HFXTC (High Frequency XTALS) 4 – 24 MHz
Internal Clock Sources
DCOCLK Digitally Controlled Oscillator MHZ (16MHz typ.)
VLOCLK Very Low Power Clock KHz
MODCLK Module Clock MHz

78. Analog to Digital Converter
32 single ended or 16 Differential Channels
12-bit Resolution
200 Kilo-Samples per Second
Sample and Hold circuitry
Internal Programmable Voltage Reference (1.2V, 2.0V, 2.5V)
Internal Conversions on Internal Sensors (E.G. Temperature Sensor)
Selectable Clocks
Single, Repeated Single, Auto-scan Sequence, and Repeated Sequence Modes
Separate Interrupt Vectors
Separate Memory Buffers
Input Voltage Comparator Windows for low signal monitoring
(MUCH more on the ADC12 Set-up at a later date)

79. Module 4: MSP430FR6989 Project #1

80. MSP430FR6989 HARDWARE PUSHBUTTONS

81. MSP430FR6989 HARDWARE
LEDS
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P1.0
P9.7

82. MSP430FR6989 Project You will create a simple microcontroller project
Follow the Steps in the next slide to create a project
DON’T SKIP ANY STEPS!

83. Project Set-up 4 0f 73 Open Code Composer Studio version 7.2.0
Select a Workspace on your U: drive
Select File  New  CCS Project
In the CCS Project window set Target to MSP430FRxxx and select MSP430FR6989
In the Project Templates and Examples window, scroll down to MPS430 DriverLib and select the Empty Project with DriverLib Source beneath that level. (See next slide.)
Enter the Project Name and click Finish
Select File  New  Source File
Enter Code
Save the File
Select Project  Rebuild Project
At this point it is essential to connect the hardware
Make sure that the Project is selected as [Active – Debug]
Select the Debug ICON
Once the GREEN ARROW comes up you can run the code
Halt execution with the RED SQUARE

84. Project Set-up
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85. MSP430FR6989 Project
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The project software shall run an Interrupt Service Routine whenever the S1 pushbutton is pressed

86. MSP430FR6989 Project
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The Interrupt Service Routine for the Pushbutton will switch the flashing LED from the RED LED (LED1) to the GREEN LED (LED2) whenever it executes

87. MSP430FR6989 Project
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You shall configure Timer A0 to generate another Interrupt every 62.5 milliseconds. To do this, you must configure the following registers: TA0CTL – Timer A0 Control Register
TA0CCTL0 – Compare 0 Control Register
TA0CCTL1 – Compare 1 Control Register
You must also write compare values to the following registers
TA0CCR0 – Compare 0 Register
TA0CCR1 – Compare 1 Register

88. MSP430FR6989 Project
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The Timer A0 Interrupt Service Routine shall toggle the state of the ACTIVE LED (either LED1 or LED2) every 500 milliseconds.

89. MSP430FR6989 Project 1. Include: driverlib.h stdio.h string.h
Can be <driverlib.h> or “driverlib.h”

90. MSP430FR6989 Project 2. Add the following function prototype:
void delay_cycles(unsigned int); This will be used to debounce the pushbutton presses which will eliminate multiple interrupts from one press.

91. MSP430FR6989 Project 3. Create the main function: void main (void) { }

92. MSP430FR6989 Project
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4. Stop the Watchdog Timer using the following TI macro (inside the main function).
WDT_A_hold(__MSP430_BASEADDRESS_WDT_A__);

93. MSP430FR6989 Project
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5. Disable the power-on high impedance mode to release all pins for configuration (do this inside main) using the following TI macro:
PMM_unlockLPM5();

94. MSP430FR6989 Project LED Initialization
6. Set Bit 0 of Port 1 as an OUTPUT
You will use the P1DIR register to do this.
This pin is connected to the RED LED.

95. MSP430FR6989 Project LED Initialization
7. Set Bit 7 of Port 9 as an OUTPUT
You will use the P9DIR register to do this.
This pin is connected to the GREEN LED

96. MSP430FR6989 Project LED Initialization
8. Turn OFF the RED LED
You will use the P1OUT register to do this.
The RED LED is on Bit 0.

97. MSP430FR6989 Project LED Initialization 9. Turn ON the GREEN LED
You will use the P9OUT register to do this.
The GREEN LED is on Bit 7.

98. MSP430FR6989 Project Pushbutton Initialization
10. CLEAR Bit 1 of PORT 1 as an INPUT
You will use P1DIR register to do this. Use &= to CLEAR the Bit 1.

99. MSP430FR6989 Project Pushbutton Initialization
11. Enable the Pull-up Resistor on P1.1 by setting Bit 1 in P1REN register
You will use P1REN register to do this
Remember that P1.1 means Bit 1 on Port 1
Remember that |= can be used to SET a bit

100. Pushbutton Initialization
MSP430FR6989 Project
Pushbutton Initialization
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12. Set Bit 1 in P1OUT to complete the Pull-up Resistor configuration for P1.1
You will use the P1OUT register to do this
Remember that P1.1 means Bit 1 on Port 1
Remember that |= can be used to SET a bit

101. Pushbutton Initialization
MSP430FR6989 Project
Pushbutton Initialization
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13. Configure the PORT 1 Interrupt for Bit 1 to trigger on a high-to-low transition by setting BIT 1 in the P1IES register.
You will use the P1IES register to do this
Remember that |= can be used to SET a bit

102. Pushbutton Initialization
MSP430FR6989 Project
Pushbutton Initialization
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14. Clear any pending interrupts on the PORT1 Bit 1 Interrupt Flag
You will use the P1IFG register to do this Clear BIT 1 to clear any pending interrupt.
Remember that &= can be used to CLEAR a bit

103. Pushbutton Initialization
MSP430FR6989 Project
Pushbutton Initialization
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15.ENABLE the PORT 1 Interrupt for Bit 1 by setting BIT 1 in the P1IE register.
You will use the P1IE register to do this
Remember that |= can be used to SET a bit

104. MSP430FR6989 Project Timer A0 Initialization
16. You will configure the TA0 Control Register (TA0CTL) to set up the Timer A0 to generate an interrupt every 62.5 milliseconds.
Calculate the HEXADECIMAL value for the entire register and write it with one command
TO FIND OUT HOW TO DO SO GO TO THE NEXT SLIDE(S)
Please refer to the next slides before writing the final command

105. MSP430FR6989 Project Timer A0 Initialization – Clock Source
17. Find the TASSEL field of 2 bits.
Select the correct bits to use the ACLK.
These bits will go in the TASSEL 2 bit field
Please refer to the next slide before writing the final command

106. MSP430FR6989 Project Timer A0 Initialization- Clock Divider
18. Find the ID field of 2 bits.
Select the correct bits to divide the ACLK by 1
These bits will go in the ID 2 bit field
Please refer to the next slide before writing the final command

107. MSP430FR6989 Project Timer A0 Initialization – Timer Mode
19. Find the MC field of 2 bits.
Select the correct bits to Put the Timer A0 in UP MODE
These bits will go in the MC 2 bit field
Please refer to the next slide before writing the final command

108. MSP430FR6989 Project Timer A0 Initialization – Other Settings
20. Let Bits 2, 1, and 0 remain 0 for now
Assume Bits 15, 14, 13, 12, 11, and 10, and 3 are 0s
Convert the 16 bit BINARY sequence of numbers that you derived in slides into a 4 character HEXADECIMAL VALUE

109. MSP430FR6989 Project Timer A0 Initialization- Initialize the Register
21. Set the TA0CTL to the HEXADECIMAL value that you derived in Slides Write the value to the TA0CTL register with a single instruction.
DO NOT USE BINARY NUMBERS TO CONFIGURE THE REGISTERS

110. MSP430FR6989 Project Timer A0 Initialization -
NOTE: Interrupts are enabled in the TA0CCTL0 Register, not the TA0CCTL1 Register
22. Enable the COMPARATOR 0 Interrupt for Timer A0 by SETTING the CCIE BIT in the TA0CCTL0 Control Register

111. MSP430FR6989 Project Timer A0 Initialization
23. Next Step. Configure the TA0 Compare Control Register for COMPARATOR NUMBER 1 (TA0CCTL1)
Please refer to the next slide before writing the final command

112. MSP430FR6989 Project Timer A0 Initialization – Output Mode
24. Find the TA0CCTL1, 3 bit field for OUTMOD
Select the Bits for RESET/SET Assume all other Bits are 0s

113. MSP430FR6989 Project Timer A0 Initialization – Initialize the Register
25. Set the TA0CCTL1 Register Value to the HEXADECIMAL value that you derived in Slide 30. Write the value to the TA0CCTL1 register with a single instruction.
DO NOT USE BINARY NUMBERS TO CONFIGURE THE REGISTERS

114. MSP430FR6989 Project Timer A0 Initialization – Timer Period
26. Set the TA0CCR0 Register to 0x07FF (Comparator for the Period)
This COMPARATOR 0 value sets the OUT1 signal when the Timer A0 counts to This also Resets the Timer A0 Counter (TA0R)
Since the ACLK is Hz, this value is 2047/32768 SECONDS.
The resulting ISR occurs every milliseconds ( 1/16th second)
The OUT1 Signal used to generate an interrupt has a frequency of 16 Hertz
DO NOT USE BINARY NUMBERS TO CONFIGURE THE REGISTERS

115. MSP430FR6989 Project Timer A0 Initialization- Timer Duty Cycle
27. Set the TA0CCR1 Register to 0x03FF
This COMPARATOR 1 value clears the OUT0 signal at a count of 1023
This gives the OUT1 signal a 50% Duty Cycle
DO NOT USE BINARY NUMBERS TO CONFIGURE THE REGISTERS

116. MSP430FR6989 Project Timer A0 Initialization Enable All Interrupts
28. Use the TI macro to enable all configured interrupts simultaneously:
__enable_interrupt();

117. MSP430FR6989 Project CONGRATULATIONS! You are done with Initialization

118. MSP430FR6989 Project Timer A0 ISR
Write the Timer A0 interrupt Service Routine
This occurs at 16 Hz or every 62.6 milliseconds

119. MSP430FR6989 Project Timer A0 ISR
Add the following variables BEFORE the main() function:
volatile unsigned char LED_Flag;
volatile unsigned int ISR_Counter;
volatile unsigned char ISR_Flag = 0;

120. MSP430FR6989 Project Timer A0 ISR
Add unused_interrupts.c to your project
DOWNLOAD IT FROM THE PROJECT 1 LAB on the ECE 3567 website.

121. MSP430FR6989 Project Timer A0 ISR
In unused_interrupts.c
comment out the #pragma vector = TIMER0_A0_VECTOR

122. MSP430FR6989 Project Timer A0 ISR
Back in main.c, AFTER the main() function,
Create the Timer A0 Interrupt Service Routine:
USE THE FOLLOWING FORMAT: #pragma vector=TIMER0_A0_VECTOR
__interrupt void Timer_A0(void) {
return; }

123. MSP430FR6989 Project Timer A0 ISR
Inside the Timer_A0 ISR:
1. Set the ISR_Flag = 1;
2. Increment the ISR_Counter++;

124. MSP430FR6989 Project Timer A0 ISR
Inside the Timer_A0 ISR:
If the ISR_Counter is greater than or equal to 8:
Compliment Bit 0 of P1OUT IF the LED_Flag equals 1
Use a new operator to COMPLIMENT BIT 0
P1OUT ^= BIT0;
(NOTE: This is the Bitwise Exclusive OR operator: A ZERO retains the bit value. A ONE INVERTS the VALUE. Pretty Cool (not to mention useful).
a b XOR

125. MSP430FR6989 Project Timer A0 ISR
Inside the Timer_A0 ISR:
If the ISR_Counter is greater than or equal to 8:
Compliment Bit 7 of P9OUT IF the LED_Flag is NOT equal to 1
(use an else)

126. MSP430FR6989 Project Timer A0 ISR
Inside the Timer_A0 ISR:
Reset the ISR_Counter to 0
LAST THING INSIDE THE IF statement for ISR_Counter >= 8
before the } for the end of the if.

127. MSP430FR6989 Project
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NOTE: Since the ISR_Counter must count to 8 before any changes take place, The lights are toggled every 8/16 or ½ SECOND.
This means that the LEDs flash at 1 Hertz.

128. MSP430FR6989 Project Pushbutton ISR
Write the Port 1 interrupt Service Routine This runs whenever the S1 Pushbutton is pressed

129. MSP430FR6989 Project Pushbutton ISR
Add the PB_Flag variable BEFORE main(): volatile unsigned int PB_Flag = 0;

130. MSP430FR6989 Project Pushbutton ISR
In unused_interrupts.c
comment out the #pragma vector = PORT1_VECTOR

131. MSP430FR6989 Project Pushbutton ISR
Back in main.c, AFTER the main() function,
Create the Port 1 Interrupt Service Routine:
USE THE FOLLOWING FORMAT: #pragma vector=PORT1_VECTOR
__interrupt void Port_1(void) {
return; }

132. MSP430FR6989 Project Pushbutton ISR
Inside the Port_1 ISR:
(BUT BEFORE THE return;)
Disable the interrupt from PORT 1 by
CLEARING BIT 1 in the P1IE register

133. MSP430FR6989 Project Pushbutton ISR
Inside the Port_1 ISR:
(BUT BEFORE THE return;)
SET the PB_Flag

134. MSP430FR6989 Project Pushbutton Debounce
Add the volatile unsigned int BEFORE main() called delay and initialize it to 2000:
volatile unsigned int delay = 2000;

135. MSP430FR6989 Project Pushbutton Debounce
Create a function to delay a fixed amount of time
called delay_cycles. do this in main.c
Begin by adding the FUNCTION PROTOTYPE BEFORE the main()
void delay_cycles ( unsigned int);

136. MSP430FR6989 Project Pushbutton Debounce
Create a function to delay a fixed amount of time
called delay_cycles. do this in main.c file BUT NOT IN THE MAIN FUNCTION.
Write the function:
void delay_cycles(unsigned int x) {
unsigned int a;
a = x;
while (a >= 1)
a--; }
return;

137. MSP430FR6989 Project The Main Loop
Program the infinite WHILE LOOP in main()
It should follow the initializations:
while(1) { }

138. MSP430FR6989 Project Main Loop - PB handler
Inside the while(1) loop, test for the PB_Flag using an if statement if(PB_Flag == 1) { }

139. MSP430FR6989 Project Main Loop - PB handler
Inside the PB_Flag IF: 1. Turn OFF both LEDS

140. MSP430FR6989 Project Main Loop - PB handler
Inside the PB_Flag IF: 2. Call the debounce delay function delay_cycles(delay);

141. MSP430FR6989 Project Main Loop - PB handler
Inside the PB_Flag IF: 3. Follow the delay with a re-reading of the pushbutton and test to see if it is still pressed:
if ((P1IN & BIT1) == 0) {
} This is a NESTED if

142. MSP430FR6989 Project Main Loop - PB handler
Inside the NESTED IF just created: 4. Compliment the LED_Flag using the ! operator
LED_Flag = !LED_Flag;

143. MSP430FR6989 Project Main Loop - PB handler
Inside the NESTED IF just created: 5. Clear the PB_Flag

144. MSP430FR6989 Project Main Loop - PB handler
AFTER the NESTED IF:
WAIT until the pushbutton is released: while((P1IN & BIT1) == 0);

145. MSP430FR6989 Project Main Loop - PB handler
AFTER the pushbutton release call the debounce delay again:
delay_cycles(delay);

146. MSP430FR6989 Project Main Loop - PB handler
Clear the Pending Interrupts for the PORT 1 ISR:
Use &= to CLEAR BIT 1 in the P1IFG register
P1IFG &= ~BIT1;

147. MSP430FR6989 Project Main Loop - PB handler
Re-enable the BIT 1 Interrupt for the PORT 1 ISR:
Use |= to SET BIT 1 in the P1IE register
P1IE |= BIT1;

148. MSP430FR6989 Project Main Loop - PB handler
This is the end of the if(PB_Flag) statement

149. MSP430FR6989 Project Main Loop – Timer A0 Handler
Add the if(ISR_Flag) to process the Timer A0 function IN THE MAIN LOOP BUT AFTER the end of if(PB_Flag==1) section:
if(ISR_Flag ==1) {
ISR_Flag = 0; }

150. MSP430FR6989 Project Main Loop
This is the end of the main() function

151. MSP430FR6989 Project Compile and Program Project #1
Demonstrate the Project to the Lab Monitor
One LED should flash at a time.
The GREEN LED should be the default after initialization
The LED should flash at 1 Hz
The Pushbutton should switch between the 2 LEDs
The Pushbutton should be free of glitches from button bounce.
Include your COMMENTED code in the Progress Report

152. This is the end of Project #1
MSP430FR6989 Project
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This is the end of Project #1