How can i go about calculating the timer values if i want to use the codes below to make the LED blink at 1Hz? How do i do calculation if i want it to blink at different Hz?
//----------------------------------------------------------------------------- // F34x_Blinky.c //----------------------------------------------------------------------------- // Copyright 2007 Silicon Laboratories, Inc. // http://www.silabs.com // // Program Description: // // This program flashes the P2.2 green LED on the C8051F34x target board // five times a second using the interrupt handler for Timer2. // // // How To Test: // // 1) Download code to a 'F34x target board // 2) Run the code and if the P2.2 LED blinks, the code works // // // FID: 34X000001 // Target: C8051F34x // Tool chain: Keil C51 7.50 / Keil EVAL C51 // Command Line: None // // Release 1.1 // -27 SEP 2006 (GP) // -Fixed #define for SYSCLK from 24.5/8 Mhz to 12/8 Mhz. // // Release 1.0 // -Initial Revision (GP) // -01 DEC 2005 //
//----------------------------------------------------------------------------- // Includes //-----------------------------------------------------------------------------
#include <c8051f340.h> // SFR declarations //----------------------------------------------------------------------------- // 16-bit SFR Definitions for 'F34x //-----------------------------------------------------------------------------
sfr16 TMR2RL = 0xca; // Timer2 reload value(stand for standard film resistor 16 bits) sfr16 TMR2 = 0xcc; // Timer2 counter
//----------------------------------------------------------------------------- // Global Constants //-----------------------------------------------------------------------------
#define SYSCLK 12000000 / 8 // SYSCLK frequency in Hz
#define BLINK_RATE 10 // Timer2 Interrupts per second
sbit LED1 = P2^2; // LED='1' means ON
//----------------------------------------------------------------------------- // Function Prototypes //-----------------------------------------------------------------------------
void OSCILLATOR_Init (void); void PORT_Init (void); void Timer2_Init (int counts); void Timer2_ISR (void);
//----------------------------------------------------------------------------- // main() Routine //----------------------------------------------------------------------------- void main (void) { PCA0MD &= ~0x40; // WDTE = 0 (clear watchdog timer // enable)
OSCILLATOR_Init (); // Initialize system clock PORT_Init (); // Initialize crossbar and GPIO
Timer2_Init (SYSCLK / 12 / BLINK_RATE); // Init Timer2 to generate // interrupts at a 10Hz rate.
EA = 1; // Enable global interrupts
while (1) {} // Spin forever }
//----------------------------------------------------------------------------- // Initialization Subroutines //-----------------------------------------------------------------------------
//----------------------------------------------------------------------------- // OSCILLATOR_Init //----------------------------------------------------------------------------- // // Return Value : None // Parameters : None // // This function initializes the system clock to (12 Mhz / 8) // //----------------------------------------------------------------------------- void OSCILLATOR_Init (void) { OSCICN = 0x80; // Configure internal oscillator for // its lowest frequency }
//----------------------------------------------------------------------7------- // PORT_Init //----------------------------------------------------------------------------- // // Return Value : None // Parameters : None // // This function configures the crossbar and GPIO ports. // // P2.2 digital push-pull LED1 //----------------------------------------------------------------------------- void PORT_Init (void) { XBR0 = 0x00; // No digital peripherals selected XBR1 = 0x40; // Enable crossbar and weak pull-ups P2MDOUT |= 0x04; // Enable LED as a push-pull output }
//----------------------------------------------------------------------------- // Timer2_Init //----------------------------------------------------------------------------- // // Return Value : None // Parameters : // 1) int counts - calculated Timer overflow rate // range is postive range of integer: 0 to 32767 // // Configure Timer2 to 16-bit auto-reload and generate an interrupt at // interval specified by <counts> using SYSCLK/48 as its time base. // //----------------------------------------------------------------------------- void Timer2_Init (int counts) { TMR2CN = 0x00; // Stop Timer2; Clear TF2; // Use SYSCLK/12 as timebase CKCON &= ~0x60; // Timer2 clocked based on T2XCLK;
TMR2RL = -counts; // Init reload values TMR2 = 0xffff; // Set to reload immediately ET2 = 1; // Enable Timer2 interrupts TR2 = 1; // Start Timer2 }
//----------------------------------------------------------------------------- // Interrupt Service Routines //-----------------------------------------------------------------------------
//----------------------------------------------------------------------------- // Timer2_ISR //----------------------------------------------------------------------------- // // This routine changes the state of the LED whenever Timer2 overflows. // //----------------------------------------------------------------------------- void Timer2_ISR (void) interrupt 5 { TF2H = 0; // Clear Timer2 interrupt flag LED1 = ~LED1; // Change state of LED }
//----------------------------------------------------------------------------- // End Of File //-----------------------------------------------------------------------------