tmk_core/tool/mbed/mbed-sdk/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/pwmout_api.c

   1 /* mbed Microcontroller Library
   2  * Copyright (c) 2006-2013 ARM Limited
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16 #include "mbed_assert.h"
  17 #include "pwmout_api.h"
  18 #include "cmsis.h"
  19 #include "pinmap.h"
  20
  21 #define TCR_CNT_EN       0x00000001
  22 #define TCR_RESET        0x00000002
  23
  24 /* To have a PWM where we can change both the period and the duty cycle,
  25  * we need an entire timer. With the following conventions:
  26  *   * MR3 is used for the PWM period
  27  *   * MR0, MR1, MR2 are used for the duty cycle
  28  */
  29 static const PinMap PinMap_PWM[] = {
  30     /* CT16B0 */
  31     {P0_8 , PWM_1, 0x02},   /* MR0 */
  32     {P0_9 , PWM_2, 0x02},   /* MR1 */
  33
  34     /* CT16B1 */
  35     {P1_9 , PWM_3, 0x01},   /* MR0 */
  36     {P1_10, PWM_4, 0x02},   /* MR1 */
  37
  38     /* CT32B0 */
  39     {P0_1 , PWM_5, 0x02},   /* MR2 */
  40
  41     {NC   , NC    ,0x00}
  42 };
  43
  44 typedef struct {
  45     uint8_t timer;
  46     uint8_t mr;
  47 } timer_mr;
  48
  49 static timer_mr pwm_timer_map[5] = {
  50     {0, 0}, /* CT16B0, MR0 */
  51     {0, 1}, /* CT16B0, MR1 */
  52
  53     {1, 0}, /* CT16B1, MR0 */
  54     {1, 1}, /* CT16B1, MR1 */
  55
  56     {2, 2}, /* CT32B0, MR2 */
  57 };
  58
  59 static LPC_TMR_TypeDef *Timers[3] = {
  60     LPC_TMR16B0, LPC_TMR16B1,
  61     LPC_TMR32B0
  62 };
  63
  64 void pwmout_init(pwmout_t* obj, PinName pin) {
  65     // determine the channel
  66     PWMName pwm = (PWMName)pinmap_peripheral(pin, PinMap_PWM);
  67     MBED_ASSERT(pwm != (uint32_t)NC);
  68
  69     obj->pwm = pwm;
  70
  71     // Timer registers
  72     timer_mr tid = pwm_timer_map[pwm];
  73     LPC_TMR_TypeDef *timer = Timers[tid.timer];
  74
  75     // Disable timer
  76     timer->TCR = 0;
  77
  78     // Power the correspondent timer
  79     LPC_SYSCON->SYSAHBCLKCTRL |= 1 << (tid.timer + 7);
  80
  81     /* Enable PWM function */
  82     timer->PWMC = (1 << 3)|(1 << 2)|(1 << 1)|(1 << 0);
  83
  84     /* Reset Functionality on MR3 controlling the PWM period */
  85     timer->MCR = 1 << 10;
  86
  87     if (timer == LPC_TMR16B0 || timer == LPC_TMR16B1) {
  88     /* Set 16-bit timer prescaler to avoid timer expire for default 20ms */
  89     /* This can be also modified by user application, but the prescaler value */
  90     /* might be trade-off to timer accuracy */
  91         timer->PR = 30;
  92     }
  93
  94     // default to 20ms: standard for servos, and fine for e.g. brightness control
  95     pwmout_period_ms(obj, 20);
  96     pwmout_write    (obj, 0);
  97
  98     // Wire pinout
  99     pinmap_pinout(pin, PinMap_PWM);
 100 }
 101
 102 void pwmout_free(pwmout_t* obj) {
 103     // [TODO]
 104 }
 105
 106 void pwmout_write(pwmout_t* obj, float value) {
 107     if (value < 0.0f) {
 108         value = 0.0;
 109     } else if (value > 1.0f) {
 110         value = 1.0;
 111     }
 112
 113     timer_mr tid = pwm_timer_map[obj->pwm];
 114     LPC_TMR_TypeDef *timer = Timers[tid.timer];
 115     uint32_t t_off = timer->MR3 - (uint32_t)((float)(timer->MR3) * value);
 116     // to avoid spike pulse when duty is 0%
 117     if (value == 0) {
 118         t_off++;
 119     }
 120
 121     timer->TCR = TCR_RESET;
 122     timer->MR[tid.mr] = t_off;
 123     timer->TCR = TCR_CNT_EN;
 124 }
 125
 126 float pwmout_read(pwmout_t* obj) {
 127     timer_mr tid = pwm_timer_map[obj->pwm];
 128     LPC_TMR_TypeDef *timer = Timers[tid.timer];
 129
 130     float v = (float)(timer->MR3 - timer->MR[tid.mr]) / (float)(timer->MR3);
 131     if (timer->MR[tid.mr] > timer->MR3) {
 132         v = 0.0f;
 133     }
 134     return (v > 1.0f) ? (1.0f) : (v);
 135 }
 136
 137 void pwmout_period(pwmout_t* obj, float seconds) {
 138     pwmout_period_us(obj, seconds * 1000000.0f);
 139 }
 140
 141 void pwmout_period_ms(pwmout_t* obj, int ms) {
 142     pwmout_period_us(obj, ms * 1000);
 143 }
 144
 145 // Set the PWM period, keeping the duty cycle the same.
 146 void pwmout_period_us(pwmout_t* obj, int us) {
 147     int i = 0;
 148     uint32_t period_ticks;
 149
 150     timer_mr tid = pwm_timer_map[obj->pwm];
 151     LPC_TMR_TypeDef *timer = Timers[tid.timer];
 152     uint32_t old_period_ticks = timer->MR3;
 153     period_ticks = (SystemCoreClock / 1000000 * us) / (timer->PR + 1);
 154
 155     timer->TCR = TCR_RESET;
 156     timer->MR3 = period_ticks;
 157
 158     // Scale the pulse width to preserve the duty ratio
 159     if (old_period_ticks > 0) {
 160         for (i=0; i<3; i++) {
 161             uint32_t t_off = period_ticks - (uint32_t)(((uint64_t)timer->MR[i] * (uint64_t)period_ticks) / (uint64_t)old_period_ticks);
 162             timer->MR[i] = t_off;
 163         }
 164     }
 165     timer->TCR = TCR_CNT_EN;
 166 }
 167
 168 void pwmout_pulsewidth(pwmout_t* obj, float seconds) {
 169     pwmout_pulsewidth_us(obj, seconds * 1000000.0f);
 170 }
 171
 172 void pwmout_pulsewidth_ms(pwmout_t* obj, int ms) {
 173     pwmout_pulsewidth_us(obj, ms * 1000);
 174 }
 175
 176 void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
 177     timer_mr tid = pwm_timer_map[obj->pwm];
 178     LPC_TMR_TypeDef *timer = Timers[tid.timer];
 179     uint32_t t_on = (uint32_t)((((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000) / (timer->PR + 1));
 180
 181     timer->TCR = TCR_RESET;
 182     if (t_on > timer->MR3) {
 183         pwmout_period_us(obj, us);
 184     }
 185     uint32_t t_off = timer->MR3 - t_on;
 186     timer->MR[tid.mr] = t_off;
 187     timer->TCR = TCR_CNT_EN;
 188 }