tool/mbed/mbed-sdk/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC13XX/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, 2}, {P1_13, PWM_1, 2},    /* MR0 */
  32     {P0_9 , PWM_2, 2}, {P1_14, PWM_2, 2},   /* MR1 */
  33     {P0_10, PWM_3, 3}, {P1_15, PWM_3, 2},   /* MR2 */
  34
  35     /* CT16B1 */
  36     {P0_21, PWM_4, 1},                      /* MR0 */
  37     {P0_22, PWM_5, 2}, {P1_23, PWM_5, 1},   /* MR1 */
  38
  39     /* CT32B0 */
  40     {P0_18, PWM_6, 2}, {P1_24, PWM_6, 1},   /* MR0 */
  41     {P0_19, PWM_7, 2}, {P1_25, PWM_7, 1},   /* MR1 */
  42     {P0_1 , PWM_8, 2}, {P1_26, PWM_8, 1},   /* MR2 */
  43
  44     /* CT32B1 */
  45     {P0_13, PWM_9 , 3}, //{P1_0, PWM_9 , 1},  /* MR0 */
  46     {P0_14, PWM_10, 3}, //{P1_1, PWM_10, 1},  /* MR1 */
  47     {P0_15, PWM_11, 3}, //{P1_2, PWM_11, 1},  /* MR2 */
  48
  49     {NC, NC, 0}
  50 };
  51
  52 typedef struct {
  53     uint8_t timer;
  54     uint8_t mr;
  55 } timer_mr;
  56
  57 static timer_mr pwm_timer_map[11] = {
  58     {0, 0}, {0, 1}, {0, 2},
  59     {1, 0}, {1, 1},
  60     {2, 0}, {2, 1}, {2, 2},
  61     {3, 0}, {3, 1}, {3, 2},
  62 };
  63
  64 static LPC_CTxxBx_Type *Timers[4] = {
  65     LPC_CT16B0, LPC_CT16B1,
  66     LPC_CT32B0, LPC_CT32B1
  67 };
  68
  69 static unsigned int pwm_clock_mhz;
  70
  71 void pwmout_init(pwmout_t* obj, PinName pin) {
  72     // determine the channel
  73     PWMName pwm = (PWMName)pinmap_peripheral(pin, PinMap_PWM);
  74     MBED_ASSERT(pwm != (uint32_t)NC);
  75
  76     obj->pwm = pwm;
  77
  78     // Timer registers
  79     timer_mr tid = pwm_timer_map[pwm];
  80     LPC_CTxxBx_Type *timer = Timers[tid.timer];
  81
  82     // Disable timer
  83     timer->TCR = 0;
  84
  85     // Power the correspondent timer
  86     LPC_SYSCON->SYSAHBCLKCTRL |= 1 << (tid.timer + 7);
  87
  88     /* Enable PWM function */
  89     timer->PWMC = (1 << 3)|(1 << 2)|(1 << 1)|(1 << 0);
  90
  91     /* Reset Functionality on MR3 controlling the PWM period */
  92     timer->MCR = 1 << 10;
  93
  94     pwm_clock_mhz = SystemCoreClock / 1000000;
  95
  96     // default to 20ms: standard for servos, and fine for e.g. brightness control
  97     pwmout_period_ms(obj, 20);
  98     pwmout_write    (obj, 0);
  99
 100     // Wire pinout
 101     pinmap_pinout(pin, PinMap_PWM);
 102 }
 103
 104 void pwmout_free(pwmout_t* obj) {
 105     // [TODO]
 106 }
 107
 108 void pwmout_write(pwmout_t* obj, float value) {
 109     if (value < 0.0f) {
 110         value = 0.0;
 111     } else if (value > 1.0f) {
 112         value = 1.0;
 113     }
 114
 115     timer_mr tid = pwm_timer_map[obj->pwm];
 116     LPC_CTxxBx_Type *timer = Timers[tid.timer];
 117     uint32_t t_off = timer->MR3 - (uint32_t)((float)(timer->MR3) * value);
 118
 119     timer->MR[tid.mr] = t_off;
 120 }
 121
 122 float pwmout_read(pwmout_t* obj) {
 123     timer_mr tid = pwm_timer_map[obj->pwm];
 124     LPC_CTxxBx_Type *timer = Timers[tid.timer];
 125
 126     float v = (float)(timer->MR3 - timer->MR[tid.mr]) / (float)(timer->MR3);
 127     return (v > 1.0f) ? (1.0f) : (v);
 128 }
 129
 130 void pwmout_period(pwmout_t* obj, float seconds) {
 131     pwmout_period_us(obj, seconds * 1000000.0f);
 132 }
 133
 134 void pwmout_period_ms(pwmout_t* obj, int ms) {
 135     pwmout_period_us(obj, ms * 1000);
 136 }
 137
 138 // Set the PWM period, keeping the duty cycle the same.
 139 void pwmout_period_us(pwmout_t* obj, int us) {
 140     int i = 0;
 141     uint32_t period_ticks = pwm_clock_mhz * us;
 142
 143     timer_mr tid = pwm_timer_map[obj->pwm];
 144     LPC_CTxxBx_Type *timer = Timers[tid.timer];
 145     uint32_t old_period_ticks = timer->MR3;
 146
 147     timer->TCR = TCR_RESET;
 148     timer->MR3 = period_ticks;
 149
 150     // Scale the pulse width to preserve the duty ratio
 151     if (old_period_ticks > 0) {
 152         for (i=0; i<3; i++) {
 153             uint32_t t_off = period_ticks - (uint32_t)(((uint64_t)timer->MR[i] * (uint64_t)period_ticks) / (uint64_t)old_period_ticks);
 154             timer->MR[i] = t_off;
 155         }
 156     }
 157     timer->TCR = TCR_CNT_EN;
 158 }
 159
 160 void pwmout_pulsewidth(pwmout_t* obj, float seconds) {
 161     pwmout_pulsewidth_us(obj, seconds * 1000000.0f);
 162 }
 163
 164 void pwmout_pulsewidth_ms(pwmout_t* obj, int ms) {
 165     pwmout_pulsewidth_us(obj, ms * 1000);
 166 }
 167
 168 void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
 169     uint32_t t_on = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000);
 170     timer_mr tid = pwm_timer_map[obj->pwm];
 171     LPC_CTxxBx_Type *timer = Timers[tid.timer];
 172
 173     timer->TCR = TCR_RESET;
 174     if (t_on > timer->MR3) {
 175         pwmout_period_us(obj, us);
 176     }
 177     uint32_t t_off = timer->MR3 - t_on;
 178     timer->MR[tid.mr] = t_off;
 179     timer->TCR = TCR_CNT_EN;
 180 }