tmk_core/tool/mbed/mbed-sdk/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC176X/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 //  PORT ID, PWM ID, Pin function
  25 static const PinMap PinMap_PWM[] = {
  26     {P1_18, PWM_1, 2},
  27     {P1_20, PWM_2, 2},
  28     {P1_21, PWM_3, 2},
  29     {P1_23, PWM_4, 2},
  30     {P1_24, PWM_5, 2},
  31     {P1_26, PWM_6, 2},
  32     {P2_0 , PWM_1, 1},
  33     {P2_1 , PWM_2, 1},
  34     {P2_2 , PWM_3, 1},
  35     {P2_3 , PWM_4, 1},
  36     {P2_4 , PWM_5, 1},
  37     {P2_5 , PWM_6, 1},
  38     {P3_25, PWM_2, 3},
  39     {P3_26, PWM_3, 3},
  40     {NC, NC, 0}
  41 };
  42
  43 __IO uint32_t *PWM_MATCH[] = {
  44     &(LPC_PWM1->MR0),
  45     &(LPC_PWM1->MR1),
  46     &(LPC_PWM1->MR2),
  47     &(LPC_PWM1->MR3),
  48     &(LPC_PWM1->MR4),
  49     &(LPC_PWM1->MR5),
  50     &(LPC_PWM1->MR6)
  51 };
  52
  53 #define TCR_PWM_EN       0x00000008
  54
  55 static unsigned int pwm_clock_mhz;
  56
  57 void pwmout_init(pwmout_t* obj, PinName pin) {
  58     // determine the channel
  59     PWMName pwm = (PWMName)pinmap_peripheral(pin, PinMap_PWM);
  60     MBED_ASSERT(pwm != (PWMName)NC);
  61
  62     obj->pwm = pwm;
  63     obj->MR = PWM_MATCH[pwm];
  64
  65     // ensure the power is on
  66     LPC_SC->PCONP |= 1 << 6;
  67
  68     // ensure clock to /4
  69     LPC_SC->PCLKSEL0 &= ~(0x3 << 12);     // pclk = /4
  70     LPC_PWM1->PR = 0;                     // no pre-scale
  71
  72     // ensure single PWM mode
  73     LPC_PWM1->MCR = 1 << 1; // reset TC on match 0
  74
  75     // enable the specific PWM output
  76     LPC_PWM1->PCR |= 1 << (8 + pwm);
  77
  78     pwm_clock_mhz = SystemCoreClock / 4000000;
  79
  80     // default to 20ms: standard for servos, and fine for e.g. brightness control
  81     pwmout_period_ms(obj, 20);
  82     pwmout_write    (obj, 0);
  83
  84     // Wire pinout
  85     pinmap_pinout(pin, PinMap_PWM);
  86 }
  87
  88 void pwmout_free(pwmout_t* obj) {
  89     // [TODO]
  90 }
  91
  92 void pwmout_write(pwmout_t* obj, float value) {
  93     if (value < 0.0f) {
  94         value = 0.0;
  95     } else if (value > 1.0f) {
  96         value = 1.0;
  97     }
  98
  99     // set channel match to percentage
 100     uint32_t v = (uint32_t)((float)(LPC_PWM1->MR0) * value);
 101
 102     // workaround for PWM1[1] - Never make it equal MR0, else we get 1 cycle dropout
 103     if (v == LPC_PWM1->MR0) {
 104         v++;
 105     }
 106
 107     *obj->MR = v;
 108
 109     // accept on next period start
 110     LPC_PWM1->LER |= 1 << obj->pwm;
 111 }
 112
 113 float pwmout_read(pwmout_t* obj) {
 114     float v = (float)(*obj->MR) / (float)(LPC_PWM1->MR0);
 115     return (v > 1.0f) ? (1.0f) : (v);
 116 }
 117
 118 void pwmout_period(pwmout_t* obj, float seconds) {
 119     pwmout_period_us(obj, seconds * 1000000.0f);
 120 }
 121
 122 void pwmout_period_ms(pwmout_t* obj, int ms) {
 123     pwmout_period_us(obj, ms * 1000);
 124 }
 125
 126 // Set the PWM period, keeping the duty cycle the same.
 127 void pwmout_period_us(pwmout_t* obj, int us) {
 128     // calculate number of ticks
 129     uint32_t ticks = pwm_clock_mhz * us;
 130
 131     // set reset
 132     LPC_PWM1->TCR = TCR_RESET;
 133
 134     // set the global match register
 135     LPC_PWM1->MR0 = ticks;
 136
 137     // Scale the pulse width to preserve the duty ratio
 138     if (LPC_PWM1->MR0 > 0) {
 139         *obj->MR = (*obj->MR * ticks) / LPC_PWM1->MR0;
 140     }
 141
 142     // set the channel latch to update value at next period start
 143     LPC_PWM1->LER |= 1 << 0;
 144
 145     // enable counter and pwm, clear reset
 146     LPC_PWM1->TCR = TCR_CNT_EN | TCR_PWM_EN;
 147 }
 148
 149 void pwmout_pulsewidth(pwmout_t* obj, float seconds) {
 150     pwmout_pulsewidth_us(obj, seconds * 1000000.0f);
 151 }
 152
 153 void pwmout_pulsewidth_ms(pwmout_t* obj, int ms) {
 154     pwmout_pulsewidth_us(obj, ms * 1000);
 155 }
 156
 157 void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
 158     // calculate number of ticks
 159     uint32_t v = pwm_clock_mhz * us;
 160
 161     // workaround for PWM1[1] - Never make it equal MR0, else we get 1 cycle dropout
 162     if (v == LPC_PWM1->MR0) {
 163         v++;
 164     }
 165
 166     // set the match register value
 167     *obj->MR = v;
 168
 169     // set the channel latch to update value at next period start
 170     LPC_PWM1->LER |= 1 << obj->pwm;
 171 }