core/pwm/pwm.c

   1 /**************************************************************************/
   2 /*!
   3     @file     pwm.c
   4     @author   K. Townsend (microBuilder.eu)
   5
   6     @brief    Simple PWM example that can be used to control a motor, dim
   7               an LED, etc.  Uses 16-bit Timer 1 and P1.9 for PWM output.
   8
   9     @section Example
  10
  11     @code
  12     #include "core/pwm/pwm.h"
  13     ...
  14
  15     // Initialises PWM output on 16-bit Timer 1 and
  16     // sets MAT0 (P1.9) as output
  17     pwmInit();
  18
  19     // Setup the pulse-width and duty-cycle
  20     pwmSetDutyCycle(50);                  // Set 50% duty cycle
  21     pwmSetFrequencyInMicroseconds(100);   // 100 millisecond pulse width
  22
  23     // Enable PWM output for exactly 50 pulses
  24     pwmStartFixed(50);
  25
  26     // Alternatively, enable PWM output indefinately
  27     pwmStart();
  28
  29     @endcode
  30
  31     @section LICENSE
  32
  33     Software License Agreement (BSD License)
  34
  35     Copyright (c) 2010, microBuilder SARL
  36     All rights reserved.
  37
  38     Redistribution and use in source and binary forms, with or without
  39     modification, are permitted provided that the following conditions are met:
  40     1. Redistributions of source code must retain the above copyright
  41     notice, this list of conditions and the following disclaimer.
  42     2. Redistributions in binary form must reproduce the above copyright
  43     notice, this list of conditions and the following disclaimer in the
  44     documentation and/or other materials provided with the distribution.
  45     3. Neither the name of the copyright holders nor the
  46     names of its contributors may be used to endorse or promote products
  47     derived from this software without specific prior written permission.
  48
  49     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ''AS IS'' AND ANY
  50     EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  51     WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  52     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
  53     DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  54     (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  55     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  56     ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  57     (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  58     SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  59 */
  60 /**************************************************************************/
  61 #include "pwm.h"
  62
  63 uint32_t pwmPulseWidth = CFG_PWM_DEFAULT_PULSEWIDTH;
  64 uint32_t pwmDutyCycle = CFG_PWM_DEFAULT_DUTYCYCLE;
  65
  66 // pwmMaxPulses is used by TIMER16_1_IRQHandler to turn PWM off after
  67 // a specified number of pulses have been sent.  This only relevant when
  68 // pwmStartFixed() is used.
  69 volatile uint32_t pwmMaxPulses = 0;
  70
  71 /**************************************************************************/
  72 /*!
  73     Initialises 16-bit Timer 1, and configures the MAT0 output (pin 1.9)
  74     to send the PWM output signal.
  75 */
  76 /**************************************************************************/
  77 void pwmInit(void)
  78 {
  79   /* Enable the clock for CT16B1 */
  80   SCB_SYSAHBCLKCTRL |= (SCB_SYSAHBCLKCTRL_CT16B1);
  81
  82   /* Configure PIO1.9 as Timer1_16 MAT0 Output */
  83   /* Alternatively, PIO1.10 (MAT1) can also be used though
  84      the initialisation code will need to be modified */
  85   IOCON_PIO1_9 &= ~IOCON_PIO1_9_FUNC_MASK;
  86   IOCON_PIO1_9 |= IOCON_PIO1_9_FUNC_CT16B1_MAT0;
  87
  88   /* Set default pulse width (MR3)*/
  89   TMR_TMR16B1MR3 = pwmPulseWidth;
  90
  91   /* Set default duty cycle (MR0) */
  92   TMR_TMR16B1MR0 = (pwmPulseWidth * (100 - pwmDutyCycle)) / 100;
  93
  94   /* Configure match control register to reset on MR3 */
  95   TMR_TMR16B1MCR = (TMR_TMR16B1MCR_MR3_RESET_ENABLED);
  96
  97   /* External Match Register Settings for PWM */
  98   TMR_TMR16B1EMR = TMR_TMR16B1EMR_EMC0_TOGGLE | TMR_TMR16B1EMR_EM0;
  99
 100   /* Disable Timer1 by default (enabled by pwmStart of pwmStartFixed) */
 101   TMR_TMR16B1TCR &= ~TMR_TMR16B1TCR_COUNTERENABLE_MASK;
 102
 103   /* Enable PWM0 and PWM3 */
 104   TMR_TMR16B1PWMC = TMR_TMR16B1PWMC_PWM0_ENABLED | TMR_TMR16B1PWMC_PWM3_ENABLED;
 105
 106   /* Make sure that the timer interrupt is enabled */
 107   NVIC_EnableIRQ(TIMER_16_1_IRQn);
 108 }
 109
 110 /**************************************************************************/
 111 /*!
 112     Starts the PWM output
 113 */
 114 /**************************************************************************/
 115 void pwmStart(void)
 116 {
 117   /* Disable interrupt on MR3 in case it was enabled by pwmStartFixed() */
 118   TMR_TMR16B1MCR  &= ~(TMR_TMR16B1MCR_MR3_INT_MASK);
 119
 120   /* Enable Timer1 */
 121   TMR_TMR16B1TCR = TMR_TMR16B1TCR_COUNTERENABLE_ENABLED;
 122 }
 123
 124 /**************************************************************************/
 125 /*!
 126     Stops the PWM output
 127 */
 128 /**************************************************************************/
 129 void pwmStop(void)
 130 {
 131   /* Disable Timer1 */
 132   TMR_TMR16B1TCR &= ~(TMR_TMR16B1TCR_COUNTERENABLE_MASK);
 133 }
 134
 135 /**************************************************************************/
 136 /*!
 137     Starts the PWM output, and stops after the specified number of
 138     pulses.
 139
 140     @param[in]  pulses
 141                 The number of pulses to generate before disabling the
 142                 PWM output.  The output is actually disabled in the
 143                 timer ISR.
 144
 145     @warning    The PWM output is actually stopped inside the 16-bit
 146                 timer ISR in "core/timer16/timer16.h".
 147 */
 148 /**************************************************************************/
 149 void pwmStartFixed(uint32_t pulses)
 150 {
 151   pwmMaxPulses = pulses;
 152
 153   /* Configure match control register to also raise an interrupt on MR3 */
 154   TMR_TMR16B1MCR  |= (TMR_TMR16B1MCR_MR3_INT_ENABLED);
 155
 156   /* Enable Timer1 (it will eventually be disabled in the ISR) */
 157   TMR_TMR16B1TCR = TMR_TMR16B1TCR_COUNTERENABLE_ENABLED;
 158 }
 159
 160 /**************************************************************************/
 161 /*!
 162     Sets the signal's duty cycle in percent (1-100).
 163
 164     @param[in]  percentage
 165                 The duty-cycle in percentage (the amount of time that
 166                 the signal is 'high' relative to the time its 'low').
 167
 168     @returns    -1 if an invalid percentage was supplied.  Value must be
 169                 between 1 and 100.
 170 */
 171 /**************************************************************************/
 172 int pwmSetDutyCycle(uint32_t percentage)
 173 {
 174   if ((percentage < 1) || (percentage > 100))
 175   {
 176     /* Duty Cycle must be a value between 1 and 100 */
 177     return -1;
 178   }
 179
 180   /* Set Duty Cycle (MR0) */
 181   TMR_TMR16B1MR0 = ((pwmPulseWidth * (100 - (pwmDutyCycle = percentage))) / 100) + 1;
 182
 183   return 0;
 184 }
 185
 186 /**************************************************************************/
 187 /*!
 188     Sets the signal's frequency/pulse-width to the specified number
 189     of ticks.
 190
 191     @param[in]  ticks
 192                 The duration in clock ticks of each full pulse.
 193
 194     @returns    -1 if a zero-value was provided for ticks.
 195 */
 196 /**************************************************************************/
 197 int pwmSetFrequencyInTicks(uint16_t ticks)
 198 {
 199   if (ticks < 1)
 200   {
 201     return -1;
 202   }
 203
 204   /* Set Pulse Width (MR3)*/
 205   TMR_TMR16B1MR3 = (pwmPulseWidth = ticks - 1);
 206
 207   /* Adjust Duty Cycle (MR0) */
 208   TMR_TMR16B1MR0 = (pwmPulseWidth * (100 - pwmDutyCycle)) / 100;
 209
 210   return 0;
 211 }
 212
 213 /**************************************************************************/
 214 /*!
 215     Sets the signal's frequency/pulse-width to the specified number
 216     of microseconds.
 217
 218     @param[in]  us
 219                 The duration in microseconds of each full pulse.
 220
 221     @returns    -1 if the supplied value exceeds the limits of the 16-bit
 222                 timer, or if a zero-value was provided.
 223
 224     @Warning    Because a 16-bit timer is used here by default, the
 225                 maximum frequency is quite small.  Running at 36MHz, the
 226                 largest possible pulse-width/frequency is ~1,82mS or
 227                 1820 microSeconds.  At 12MHz its 5461 uS, at 48MHz
 228                 its 1365 uS, at 72MHz its 909uS.
 229 */
 230 /**************************************************************************/
 231 int pwmSetFrequencyInMicroseconds(uint16_t us)
 232 {
 233   if (us < 1)
 234   {
 235     return -1;
 236   }
 237
 238   uint32_t ticks = (((CFG_CPU_CCLK/SCB_SYSAHBCLKDIV) / 1000000) * us);
 239   if (ticks > 0xFFFF)
 240   {
 241     /* Delay exceeds the upper limit for the 16-bit timer */
 242     return -1;
 243   }
 244
 245   /* Set Pulse Width (MR3)*/
 246   TMR_TMR16B1MR3 = (pwmPulseWidth = ticks - 1);
 247
 248   /* Adjust Duty Cycle (MR0) */
 249   TMR_TMR16B1MR0 = ((pwmPulseWidth * (100 - pwmDutyCycle)) / 100) + 1;
 250
 251   return 0;
 252 }
 253
 254