main.cpp

00001 #include "mbed.h"
00002 
00003 // Hardware Quadrature Encoder ABZ for Nucleo F401RE
00004 // Output on debug port to host PC @ 9600 baud
00005 // 
00006 // By Nigel Webb, November 2014
00007 
00008 /* Connections
00009    PA_0 = Encoder A
00010    PA_1 = Encoder B
00011    PA_4 = Encoder Z 
00012 */
00013 
00014 InterruptIn ZPulse(PA_4) ; // Setup Interrupt for Z Pulse
00015 
00016 void EncoderInitialise(void) {
00017     // configure GPIO PA0 & PA1 as inputs for Encoder
00018     RCC->AHB1ENR |= 0x00000001;  // Enable clock for GPIOA
00019  
00020     GPIOA->MODER   |= GPIO_MODER_MODER0_1 | GPIO_MODER_MODER1_1 ;           //PA0 & PA1 as Alternate Function   /*!< GPIO port mode register,               Address offset: 0x00      */
00021     GPIOA->OTYPER  |= GPIO_OTYPER_OT_0 | GPIO_OTYPER_OT_1 ;                 //PA0 & PA1 as Inputs               /*!< GPIO port output type register,        Address offset: 0x04      */
00022     GPIOA->OSPEEDR |= GPIO_OSPEEDER_OSPEEDR0 | GPIO_OSPEEDER_OSPEEDR1 ;     // Low speed                        /*!< GPIO port output speed register,       Address offset: 0x08      */
00023     GPIOA->PUPDR   |= GPIO_PUPDR_PUPDR0_1 | GPIO_PUPDR_PUPDR1_1 ;           // Pull Down                        /*!< GPIO port pull-up/pull-down register,  Address offset: 0x0C      */
00024     GPIOA->AFR[0]  |= 0x00000011 ;                                          //  AF01 for PA0 & PA1              /*!< GPIO alternate function registers,     Address offset: 0x20-0x24 */
00025     GPIOA->AFR[1]  |= 0x00000000 ;                                          //                                  /*!< GPIO alternate function registers,     Address offset: 0x20-0x24 */
00026    
00027     // configure TIM2 as Encoder input
00028     RCC->APB1ENR |= 0x00000001;  // Enable clock for TIM2
00029  
00030     TIM2->CR1   = 0x0001;     // CEN(Counter ENable)='1'     < TIM control register 1
00031     TIM2->SMCR  = 0x0003;     // SMS='011' (Encoder mode 3)  < TIM slave mode control register
00032     TIM2->CCMR1 = 0xF1F1;     // CC1S='01' CC2S='01'         < TIM capture/compare mode register 1
00033     TIM2->CCMR2 = 0x0000;     //                             < TIM capture/compare mode register 2
00034     TIM2->CCER  = 0x0011;     // CC1P CC2P                   < TIM capture/compare enable register
00035     TIM2->PSC   = 0x0000;     // Prescaler = (0+1)           < TIM prescaler
00036     TIM2->ARR   = 0xffffffff; // reload at 0xfffffff         < TIM auto-reload register
00037   
00038     TIM2->CNT = 0x0000;  //reset the counter before we use it  
00039 }
00040 
00041 // Z Pulse routine
00042 void ZeroEncoderCount() {
00043     TIM2->CNT=0 ; //reset count to zero
00044 }
00045 
00046 int main() {
00047     EncoderInitialise() ;
00048     
00049     ZPulse.rise(&ZeroEncoderCount) ; //Setup Interrupt for rising edge of Z pulse 
00050     ZPulse.mode(PullDown) ; // Set input as pull down
00051      
00052     unsigned int EncoderPosition ;
00053     
00054     while (true) {
00055         // Print Encoder Quadrature count to debug port every 0.5 seconds
00056         EncoderPosition = TIM2->CNT ; // Get current position from Encoder
00057         printf("Encoder Position %i\r\n", EncoderPosition); 
00058         wait(0.5);
00059     }
00060    
00061        
00062 }