lib_ClockCounter.cpp

00001 /** Mbed Library Clock Counter
00002 * Hardware pulse counter with TIMER2 (CAP2.0 or CAP2.1) on Mbed LPC1768
00003 *
00004 * Counts signal transitions on p30(CAP2.0) or p29(CAP2.1) for LPC1768 target.
00005 * Can detecte rising, falling or both signal edge.
00006 * Return the signal edge count during a period in seconds.
00007 * In theory (Shannon's theorem) input signal frequency can up to 48 MHz with 96 MHz CCLK.
00008 * But only tested with frequencys up to 20 MHz and it work.
00009 *
00010 * Example :
00011 * @code
00012 * #include "mbed.h"
00013 * #include "lib_ClockCounter.h"
00014 *
00015 * Serial pc(USBTX, USBRX);
00016 * ClockCounter Frequency;
00017 * 
00018 * int main()
00019 * {
00020 *     while(1) pc.printf("Frequency = %d Hz\r\n", Frequency.getCount());
00021 * }
00022 * @endcode
00023 */
00024 
00025 #include "lib_ClockCounter.h"
00026 #include <cstdint>
00027 
00028 ClockCounter::ClockCounter(PinName PIN_CAP2, edgeDetection EDGE)
00029 {
00030     _count = 0;
00031     _selectPin = NC;
00032     switch(PIN_CAP2)
00033     {
00034         case p30: case p29:
00035                                                                     // PCONP => Power Mode Control register
00036             LPC_SC->PCONP |= (0x1<<22);                             // Bit(22) 1 => Timer2 power on
00037                                                                     // PCLKSEL1 => Peripheral Clock Selection register 1
00038             LPC_SC->PCLKSEL1 |= (0x1<<12);                          // Bits(13,12) 01 => PCLK_TIMER2 = CCLK(96 MHz)
00039                                                                     // TCR => Timer Control Register
00040             LPC_TIM2->TCR = 0x0;                                    // Bits(1,0) 00 => Timer2 disabled
00041                                                                     // PINSEL0 => Pin Function Select register 0
00042             LPC_PINCON->PINSEL0 |= (0x3<<((PIN_CAP2==p30)?8:10));   // Bits(9,8) 11 => pin function CAP2.0 (p30), Bits(11,10) 11 => pin function CAP2.1 (p29)
00043                                                                     // CTCR => Count Control Register
00044             LPC_TIM2->CTCR = ((PIN_CAP2==p30)?0:4)+EDGE;            // Bits(3,2) 00 => CAP2.0 (p30 signal is counter clock) or 11 => CAP2.1 (p29 signal is counter clock), Bits(1,0) XX => timer is incremented on edge
00045                                                                     // CCR => Capture Control Register
00046             LPC_TIM2->CCR = 0x0;                                    // Bits(5,4,3,2,1,0) 000000 => capture and interrupt on event disabled
00047         break;
00048         default:
00049         break;
00050     }
00051 }
00052 
00053 void ClockCounter::setPin(PinName PIN_CAP2, edgeDetection EDGE)
00054 {
00055     _selectPin = PIN_CAP2;
00056     switch(PIN_CAP2)
00057     {
00058         case p30: case p29:
00059                                                                     // PCONP => Power Mode Control register
00060             LPC_SC->PCONP |= (0x1<<22);                             // Bit(22) 1 => Timer2 power on
00061                                                                     // PCLKSEL1 => Peripheral Clock Selection register 1
00062             LPC_SC->PCLKSEL1 |= (0x1<<12);                          // Bits(13,12) 01 => PCLK_TIMER2 = CCLK(96 MHz)
00063                                                                     // TCR => Timer Control Register
00064             LPC_TIM2->TCR = 0x0;                                    // Bits(1,0) 00 => Timer2 disabled
00065                                                                     // PINSEL0 => Pin Function Select register 0
00066             LPC_PINCON->PINSEL0 |= (0x3<<((PIN_CAP2==p30)?8:10));   // Bits(9,8) 11 => pin function CAP2.0 (p30), Bits(11,10) 11 => pin function CAP2.1 (p29)
00067                                                                     // CTCR => Count Control Register
00068             LPC_TIM2->CTCR = ((PIN_CAP2==p30)?0:4)+EDGE;            // Bits(3,2) 00 => CAP2.0 (p30 signal is counter clock) or 11 => CAP2.1 (p29 signal is counter clock), Bits(1,0) XX => timer is incremented on edge
00069                                                                     // CCR => Capture Control Register
00070             LPC_TIM2->CCR = 0x0;                                    // Bits(5,4,3,2,1,0) 000000 => capture and interrupt on event disabled
00071         break;
00072         default:
00073         break;
00074     }
00075 }
00076 
00077 void ClockCounter::startCount(void)
00078 {
00079                                                                     // TCR => Timer Control Register
00080     LPC_TIM2->TCR = 0x2;                                            // Bits(1,0) 10 => Timer2 count reset
00081     LPC_TIM2->TCR = 0x1;                                            // Bits(1,0) 01 => Timer2 enabled
00082 }
00083 
00084 int ClockCounter::stopCount(void)
00085 {
00086     LPC_TIM2->TCR = 0x0;                                            // Bits(1,0) 00 => Timer2 disabled
00087     uint32_t TC = LPC_TIM2->TC;                                     // TC => Timer Counter
00088     _selectPin = NC;
00089     return TC;
00090 }
00091 
00092 int ClockCounter::getCount(int period)
00093 {
00094                                                                     // TCR => Timer Control Register
00095     LPC_TIM2->TCR = 0x2;                                            // Bits(1,0) 10 => Timer2 count reset
00096     LPC_TIM2->TCR = 0x1;                                            // Bits(1,0) 01 => Timer2 enabled
00097     wait_us(period);
00098     LPC_TIM2->TCR = 0x0;                                            // Bits(1,0) 00 => Timer2 disabled
00099     return LPC_TIM2->TC;                                            // TC => Timer Counter
00100 }
00101 
00102 PinName ClockCounter::getPin(void)
00103 {
00104     return _selectPin;
00105 }