Output Compare is a powerful feature of embedded world. The PIC32 Output Compare module compares the values stored in the OCxR and/or the OCxRS registers to the value in the selected timer. When a match occurs, the Output Compare module generates an event based on the selected mode of operation. The following are some of the key features:
•Multiple Output Compare modules in a device
•Programmable interrupt generation on compare event
•Single and Dual Compare modes
•Single and continuous output pulse generation
•Pulse-Width Modulation (PWM) mode
•Hardware-based PWM Fault detection and automatic output disable
•Programmable selection of 16-bit or 32-bit time bases
•Can operate from either of two available 16-bit time bases or a single 32-bit time base
•ADC event trigger
At the moment, I just set the Output Compare work in PWM mode. The PWM duty is increasing by little and little at the beginning. Then PWM duty is decreasing by little and little. This application run on my PIC32MZ EC Starter Kit, and the PWM drives a LED. So you can see the LED flux is changing from dim to bright and reverse. Blow is the copy of my application code.
#include <xc.h> #include <sys/attribs.h> #pragma config FMIIEN = ON // Ethernet RMII/MII Enable (MII Enabled) // need a 25MHz XTAL in MII mode, a 50MHz Clock in RMII mode. #pragma config FETHIO = ON // Ethernet I/O Pin Select (Default Ethernet I/O) #pragma config PGL1WAY = ON // Permission Group Lock One Way Configuration (Allow only one reconfiguration) #pragma config PMDL1WAY = ON // Peripheral Module Disable Configuration (Allow only one reconfiguration) #pragma config IOL1WAY = ON // Peripheral Pin Select Configuration (Allow only one reconfiguration) #pragma config FUSBIDIO = OFF // USB USBID Selection (Controlled by Port Function) // DEVCFG2 7FF9B11A #pragma config FPLLIDIV = DIV_3 // System PLL Input Divider (3x Divider) #pragma config FPLLRNG = RANGE_5_10_MHZ // System PLL Input Range (5-10 MHz Input) #pragma config FPLLICLK = PLL_POSC // System PLL Input Clock Selection (POSC is input to the System PLL) #pragma config FPLLMULT = MUL_50 // System PLL Multiplier (PLL Multiply by 50) //PLL must output between 350 and 700 MHz #pragma config FPLLODIV = DIV_2 // System PLL Output Clock Divider (2x Divider) #pragma config UPLLFSEL = FREQ_24MHZ // USB PLL Input Frequency Selection (USB PLL input is 24 MHz) #pragma config UPLLEN = OFF // USB PLL Enable (USB PLL is disabled) // DEVCFG1 7F7F3839 #pragma config FNOSC = SPLL // Oscillator Selection Bits (System PLL) #pragma config DMTINTV = WIN_127_128 // DMT Count Window Interval (Window/Interval value is 127/128 counter value) #pragma config FSOSCEN = OFF // Secondary Oscillator Enable (Disable SOSC) #pragma config IESO = OFF // Internal/External Switch Over (Disabled) #pragma config POSCMOD = EC // Primary Oscillator Configuration (External clock mode) #pragma config OSCIOFNC = ON // CLKO Output Signal Active on the OSCO Pin (Enabled) #pragma config FCKSM = CSDCMD // Clock Switching and Monitor Selection (Clock Switch Disabled, FSCM Disabled) #pragma config WDTPS = PS1048576 // Watchdog Timer Postscaler (1:1048576) #pragma config WDTSPGM = STOP // Watchdog Timer Stop During Flash Programming (WDT stops during Flash programming) #pragma config WINDIS = NORMAL // Watchdog Timer Window Mode (Watchdog Timer is in non-Window mode) #pragma config FWDTEN = OFF // Watchdog Timer Enable (WDT Disabled) #pragma config FWDTWINSZ = WINSZ_25 // Watchdog Timer Window Size (Window size is 25%) #pragma config DMTCNT = DMT31 // Deadman Timer Count Selection (2^31 (2147483648)) #pragma config FDMTEN = OFF // Deadman Timer Enable (Deadman Timer is disabled) // DEVCFG0 FFFFFFF7 #pragma config DEBUG = OFF // Background Debugger Enable (Debugger is disabled) #pragma config JTAGEN = ON // JTAG Enable (JTAG Port Enabled) #pragma config ICESEL = ICS_PGx2 // ICE/ICD Comm Channel Select (Communicate on PGEC2/PGED2) #pragma config TRCEN = ON // Trace Enable (Trace features in the CPU are enabled) #pragma config BOOTISA = MIPS32 // Boot ISA Selection (Boot code and Exception code is MIPS32) #pragma config FECCCON = OFF_UNLOCKED // Dynamic Flash ECC Configuration (ECC and Dynamic ECC are disabled (ECCCON bits are writable)) #pragma config FSLEEP = OFF // Flash Sleep Mode (Flash is powered down when the device is in Sleep mode) #pragma config DBGPER = ALLOW_PG2 // Debug Mode CPU Access Permission (Allow CPU access to Permission Group 2 permission regions) #pragma config EJTAGBEN = NORMAL // EJTAG Boot (Normal EJTAG functionality) // DEVCP0 #pragma config CP = OFF // Code Protect (Protection Disabled) #define Mvec_Interrupt() INTCONSET = 0x1000; asm volatile("ei"); #define OC1_VALUE (PORTD & 0x2) #define OC_MAX (0x7A120) #define OC_MIN (0x0) #define STEP_VALUE (500) #define LED_IOCTL() TRISHCLR = (1<<0) #define LED_SETON() LATHSET = (1<<0) #define LED_SETOFF() LATHCLR = (1<<0) #define LED_ONOFF() LATHINV = (1<<0) #define LED_OPEN() ANSELH &= 0xFFFFFFFE typedef enum _eRUN_MODE { Stable1, Welcome, Stable2, Goodbye, } eRUN_MODE; eRUN_MODE LED_RunMode; void OC1_Init(void) { OC1CON = 0x0000; RPD1R = 0xC; OC1RS = OC_MIN; OC1R = OC_MIN; OC1CON = 0x2E; OC1CONSET = 0x8000; // Enable OC } void LED_Init(void) { LED_SETOFF(); LED_OPEN(); LED_IOCTL(); LED_RunMode = Stable1; } void T23_Init(void) { T2CON = 0x0; T3CON = 0x0; TMR2 = 0; TMR3 = 0; //IPC3SET = 0x50000; IPC3SET = 0x120000; IEC0SET = 0x4000; IFS0CLR = 0x4000; PR2 = 0xA120; PR3 = 0x7; T2CON = 0x0008; T2CON |= 0x8000; } void T45_Init(void) { T4CON = 0; T5CON = 0; TMR4 = 0; TMR5 = 0; IPC6SET = 0x6; IFS0CLR = 0x1000000; IEC0SET = 0x1000000; PR4 = 0xE100; PR5 = 0x05F5; T4CON = 0x0008; T4CON |= 0x8000; } void LED_Scheduler(void) { if (OC1_VALUE == 0x2) { LED_SETON(); } else { LED_SETOFF(); } } void __ISR(_TIMER_3_VECTOR,ipl4AUTO) T23_Handler(void) { if (LED_RunMode == Stable1) { ; // do nothing } else if (LED_RunMode == Stable2) { ; // do nothing } else if (LED_RunMode == Welcome) { OC1RS = OC1RS + STEP_VALUE; if (OC1RS >= OC_MAX) { T4CON = 0x0008; TMR4 = 0; TMR5 = 0; PR4 = 0xE100; PR5 = 0x05F5; T4CON = 0x8008; IFS0CLR = 0x1000000; LED_RunMode = Stable2; } } else // LED_RunMode == Goodbye { OC1RS = OC1RS - STEP_VALUE; if (OC1RS == OC_MIN) { T4CON = 0x0008; TMR4 = 0; TMR5 = 0; PR4 = 0xE100; PR5 = 0x05F5; T4CON = 0x8008; IFS0CLR = 0x1000000; LED_RunMode = Stable1; } } TMR2 = 0; TMR3 = 0; IFS0CLR = 0x4000; Nop(); } void __ISR(_TIMER_5_VECTOR,ipl1AUTO) T45_Handler(void) { if (LED_RunMode == Stable1) { LED_RunMode = Welcome; //PR5 = 0x98; PR4 = 0x9680; PR5 = 0x98; } else if (LED_RunMode == Welcome) { ; // do nothing } else if (LED_RunMode == Stable2) { LED_RunMode = Goodbye; //PR5 = 0x98; PR4 = 0x9680; PR5 = 0x98; } else // LED_RunMode == Goodbye { ; // do nothing } TMR4 = 0; TMR5 = 0; IFS0CLR = 0x1000000; Nop(); } void main(void) { LED_Init(); OC1_Init(); T23_Init(); T45_Init(); Mvec_Interrupt(); while(1) { LED_Scheduler(); } }