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Frequency counter using LPC1768 hardware counter, tested up-to 11MHz forked from https://developer.mbed.org/users/mio/code/5MHzOSC/
Fork of 5MHzOSC by
main.cpp
- Committer:
- mio
- Date:
- 2013-05-26
- Revision:
- 2:bff82681a822
- Parent:
- 1:2a347c40b1da
- Child:
- 3:603f4efe3985
File content as of revision 2:bff82681a822:
// // CLOCK OUT to PWM1[6] Sample with Freq Counter using Cap2.0 // For LPC1768-mbed // // Reference: 5MHz Clock Out Code and Comment - http://mbed.org/forum/mbed/topic/733/ // // !! To Self Measurement Output Clock, Connect p21 <-> p30 with jumper wire. // #include "mbed.h" PwmOut fmclck(p21); // for RESERVE pin21 as PWM1[6] DigitalIn clkin(p30); // for RESERVE pin30 as CAP2[0] // Reset Counter and Count Start void P30_RESET_CTR(void) { LPC_TIM2->TCR = 2; // Reset the counter (bit1<=1,bit0<=0) LPC_TIM2->TCR = 1; // UnReset counter (bit1<=0,bit0<=1) } // Get Counter Value int P30_GET_CTR(void) { return LPC_TIM2->TC; // Read the counter value } // Setting p30 to Cap2.0 void P30_INIT_CTR(void) { LPC_SC->PCONP |= 1 << 22; // 1)Power up TimerCounter2 (bit22) LPC_PINCON->PINSEL0 |= 3 << 8; // 2)Set P0[4] to CAP2[0] LPC_TIM2->TCR = 2; // 3)Counter Reset (bit1<=1,bit0<=0) LPC_TIM2->CTCR = 1; // 4)Count on riging edge Cap2[0] LPC_TIM2->CCR = 0; // 5)Input Capture Disabled LPC_TIM2->TCR = 1; // 6)Counter Start (bit1<=0,bit0<=1) } // Clock Output From pin21(PWM6) // Set Clock Freq with div. // if mbed is running at 96MHz, div is set 96 to Get 1MHz. void PWM6_SETCLK(int div) { LPC_PWM1->TCR = (1 << 1); // 1)Reset counter, disable PWM LPC_SC->PCLKSEL0 &= ~(0x3 << 12); LPC_SC->PCLKSEL0 |= (1 << 12); // 2)Set peripheral clock divider to /1, i.e. system clock LPC_PWM1->MR0 = div - 1; // 3)Match Register 0 is shared period counter for all PWM1 LPC_PWM1->MR6 = 9; // 3)Pin 21 is PWM1[6], so Match Register 6 LPC_PWM1->LER |= 1; // 4)Start updating at next period start LPC_PWM1->TCR = (1 << 0) || (1 << 3); // 5)Enable counter and PWM } int main() { PWM6_SETCLK(96) ; // Outout mbed's "PWM6" pin to 96MHZ/19 = 5.052MHz (Approx) P30_INIT_CTR(); while(1){ P30_RESET_CTR(); wait(1.0); // Gate time for count printf("pin30 Freq = %d (Hz)\r\n",P30_GET_CTR()); } }