Lee Kai Xuan / mbed-os

mbed-os

Fork of mbed-os by erkin yucel

targets/TARGET_NXP/TARGET_LPC11UXX/pwmout_api.c@0:f269e3021894, 2016-10-23 (annotated)

Committer:
elessair
Date:
Sun Oct 23 15:10:02 2016 +0000
Revision:
0:f269e3021894
Initial commit

Who changed what in which revision?

UserRevisionLine numberNew contents of line
elessair 0:f269e3021894 1 /* mbed Microcontroller Library
elessair 0:f269e3021894 2 * Copyright (c) 2006-2013 ARM Limited
elessair 0:f269e3021894 3 *
elessair 0:f269e3021894 4 * Licensed under the Apache License, Version 2.0 (the "License");
elessair 0:f269e3021894 5 * you may not use this file except in compliance with the License.
elessair 0:f269e3021894 6 * You may obtain a copy of the License at
elessair 0:f269e3021894 7 *
elessair 0:f269e3021894 8 * http://www.apache.org/licenses/LICENSE-2.0
elessair 0:f269e3021894 9 *
elessair 0:f269e3021894 10 * Unless required by applicable law or agreed to in writing, software
elessair 0:f269e3021894 11 * distributed under the License is distributed on an "AS IS" BASIS,
elessair 0:f269e3021894 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
elessair 0:f269e3021894 13 * See the License for the specific language governing permissions and
elessair 0:f269e3021894 14 * limitations under the License.
elessair 0:f269e3021894 15 */
elessair 0:f269e3021894 16 #include "mbed_assert.h"
elessair 0:f269e3021894 17 #include "pwmout_api.h"
elessair 0:f269e3021894 18 #include "cmsis.h"
elessair 0:f269e3021894 19 #include "pinmap.h"
elessair 0:f269e3021894 20 #include "PeripheralPins.h" // For the Peripheral to Pin Definitions found in the individual Target's Platform
elessair 0:f269e3021894 21
elessair 0:f269e3021894 22 #define TCR_CNT_EN 0x00000001
elessair 0:f269e3021894 23 #define TCR_RESET 0x00000002
elessair 0:f269e3021894 24
elessair 0:f269e3021894 25 typedef struct {
elessair 0:f269e3021894 26 uint8_t timer;
elessair 0:f269e3021894 27 uint8_t mr;
elessair 0:f269e3021894 28 } timer_mr;
elessair 0:f269e3021894 29
elessair 0:f269e3021894 30 static timer_mr pwm_timer_map[11] = {
elessair 0:f269e3021894 31 {0, 0}, {0, 1}, {0, 2},
elessair 0:f269e3021894 32 {1, 0}, {1, 1},
elessair 0:f269e3021894 33 {2, 0}, {2, 1}, {2, 2},
elessair 0:f269e3021894 34 {3, 0}, {3, 1}, {3, 2},
elessair 0:f269e3021894 35 };
elessair 0:f269e3021894 36
elessair 0:f269e3021894 37 static LPC_CTxxBx_Type *Timers[4] = {
elessair 0:f269e3021894 38 LPC_CT16B0, LPC_CT16B1,
elessair 0:f269e3021894 39 LPC_CT32B0, LPC_CT32B1
elessair 0:f269e3021894 40 };
elessair 0:f269e3021894 41
elessair 0:f269e3021894 42 void pwmout_init(pwmout_t* obj, PinName pin) {
elessair 0:f269e3021894 43 // determine the channel
elessair 0:f269e3021894 44 PWMName pwm = (PWMName)pinmap_peripheral(pin, PinMap_PWM);
elessair 0:f269e3021894 45 MBED_ASSERT(pwm != (PWMName)NC);
elessair 0:f269e3021894 46
elessair 0:f269e3021894 47 obj->pwm = pwm;
elessair 0:f269e3021894 48
elessair 0:f269e3021894 49 // Timer registers
elessair 0:f269e3021894 50 timer_mr tid = pwm_timer_map[pwm];
elessair 0:f269e3021894 51 LPC_CTxxBx_Type *timer = Timers[tid.timer];
elessair 0:f269e3021894 52
elessair 0:f269e3021894 53 // Disable timer
elessair 0:f269e3021894 54 timer->TCR = 0;
elessair 0:f269e3021894 55
elessair 0:f269e3021894 56 // Power the correspondent timer
elessair 0:f269e3021894 57 LPC_SYSCON->SYSAHBCLKCTRL |= 1 << (tid.timer + 7);
elessair 0:f269e3021894 58
elessair 0:f269e3021894 59 /* Enable PWM function */
elessair 0:f269e3021894 60 timer->PWMC = (1 << 3)|(1 << 2)|(1 << 1)|(1 << 0);
elessair 0:f269e3021894 61
elessair 0:f269e3021894 62 /* Reset Functionality on MR3 controlling the PWM period */
elessair 0:f269e3021894 63 timer->MCR = 1 << 10;
elessair 0:f269e3021894 64
elessair 0:f269e3021894 65 // default to 20ms: standard for servos, and fine for e.g. brightness control
elessair 0:f269e3021894 66 pwmout_period_ms(obj, 20);
elessair 0:f269e3021894 67 pwmout_write (obj, 0);
elessair 0:f269e3021894 68
elessair 0:f269e3021894 69 // Wire pinout
elessair 0:f269e3021894 70 pinmap_pinout(pin, PinMap_PWM);
elessair 0:f269e3021894 71 }
elessair 0:f269e3021894 72
elessair 0:f269e3021894 73 void pwmout_free(pwmout_t* obj) {
elessair 0:f269e3021894 74 // [TODO]
elessair 0:f269e3021894 75 }
elessair 0:f269e3021894 76
elessair 0:f269e3021894 77 void pwmout_write(pwmout_t* obj, float value) {
elessair 0:f269e3021894 78 if (value < 0.0f) {
elessair 0:f269e3021894 79 value = 0.0;
elessair 0:f269e3021894 80 } else if (value > 1.0f) {
elessair 0:f269e3021894 81 value = 1.0;
elessair 0:f269e3021894 82 }
elessair 0:f269e3021894 83
elessair 0:f269e3021894 84 timer_mr tid = pwm_timer_map[obj->pwm];
elessair 0:f269e3021894 85 LPC_CTxxBx_Type *timer = Timers[tid.timer];
elessair 0:f269e3021894 86 uint32_t t_off = timer->MR3 - (uint32_t)((float)(timer->MR3) * value);
elessair 0:f269e3021894 87
elessair 0:f269e3021894 88 timer->MR[tid.mr] = t_off;
elessair 0:f269e3021894 89 }
elessair 0:f269e3021894 90
elessair 0:f269e3021894 91 float pwmout_read(pwmout_t* obj) {
elessair 0:f269e3021894 92 timer_mr tid = pwm_timer_map[obj->pwm];
elessair 0:f269e3021894 93 LPC_CTxxBx_Type *timer = Timers[tid.timer];
elessair 0:f269e3021894 94
elessair 0:f269e3021894 95 float v = (float)(timer->MR3 - timer->MR[tid.mr]) / (float)(timer->MR3);
elessair 0:f269e3021894 96 return (v > 1.0f) ? (1.0f) : (v);
elessair 0:f269e3021894 97 }
elessair 0:f269e3021894 98
elessair 0:f269e3021894 99 void pwmout_period(pwmout_t* obj, float seconds) {
elessair 0:f269e3021894 100 pwmout_period_us(obj, seconds * 1000000.0f);
elessair 0:f269e3021894 101 }
elessair 0:f269e3021894 102
elessair 0:f269e3021894 103 void pwmout_period_ms(pwmout_t* obj, int ms) {
elessair 0:f269e3021894 104 pwmout_period_us(obj, ms * 1000);
elessair 0:f269e3021894 105 }
elessair 0:f269e3021894 106
elessair 0:f269e3021894 107 // Set the PWM period, keeping the duty cycle the same.
elessair 0:f269e3021894 108 void pwmout_period_us(pwmout_t* obj, int us) {
elessair 0:f269e3021894 109 int i = 0;
elessair 0:f269e3021894 110 uint32_t period_ticks = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000);
elessair 0:f269e3021894 111
elessair 0:f269e3021894 112 timer_mr tid = pwm_timer_map[obj->pwm];
elessair 0:f269e3021894 113 LPC_CTxxBx_Type *timer = Timers[tid.timer];
elessair 0:f269e3021894 114 uint32_t old_period_ticks = timer->MR3;
elessair 0:f269e3021894 115
elessair 0:f269e3021894 116 // for 16bit timer, set prescaler to avoid overflow
elessair 0:f269e3021894 117 if (timer == LPC_CT16B0 || timer == LPC_CT16B1) {
elessair 0:f269e3021894 118 uint16_t high_period_ticks = period_ticks >> 16;
elessair 0:f269e3021894 119 timer->PR = high_period_ticks;
elessair 0:f269e3021894 120 period_ticks /= (high_period_ticks + 1);
elessair 0:f269e3021894 121 }
elessair 0:f269e3021894 122
elessair 0:f269e3021894 123 timer->TCR = TCR_RESET;
elessair 0:f269e3021894 124 timer->MR3 = period_ticks;
elessair 0:f269e3021894 125
elessair 0:f269e3021894 126 // Scale the pulse width to preserve the duty ratio
elessair 0:f269e3021894 127 if (old_period_ticks > 0) {
elessair 0:f269e3021894 128 for (i=0; i<3; i++) {
elessair 0:f269e3021894 129 uint32_t t_off = period_ticks - (uint32_t)(((uint64_t)timer->MR[i] * (uint64_t)period_ticks) / (uint64_t)old_period_ticks);
elessair 0:f269e3021894 130 timer->MR[i] = t_off;
elessair 0:f269e3021894 131 }
elessair 0:f269e3021894 132 }
elessair 0:f269e3021894 133 timer->TCR = TCR_CNT_EN;
elessair 0:f269e3021894 134 }
elessair 0:f269e3021894 135
elessair 0:f269e3021894 136 void pwmout_pulsewidth(pwmout_t* obj, float seconds) {
elessair 0:f269e3021894 137 pwmout_pulsewidth_us(obj, seconds * 1000000.0f);
elessair 0:f269e3021894 138 }
elessair 0:f269e3021894 139
elessair 0:f269e3021894 140 void pwmout_pulsewidth_ms(pwmout_t* obj, int ms) {
elessair 0:f269e3021894 141 pwmout_pulsewidth_us(obj, ms * 1000);
elessair 0:f269e3021894 142 }
elessair 0:f269e3021894 143
elessair 0:f269e3021894 144 void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
elessair 0:f269e3021894 145 timer_mr tid = pwm_timer_map[obj->pwm];
elessair 0:f269e3021894 146 LPC_CTxxBx_Type *timer = Timers[tid.timer];
elessair 0:f269e3021894 147 uint32_t t_on = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000 / (timer->PR + 1));
elessair 0:f269e3021894 148
elessair 0:f269e3021894 149 timer->TCR = TCR_RESET;
elessair 0:f269e3021894 150 if (t_on > timer->MR3) {
elessair 0:f269e3021894 151 pwmout_period_us(obj, us);
elessair 0:f269e3021894 152 t_on = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000 / (timer->PR + 1));
elessair 0:f269e3021894 153 }
elessair 0:f269e3021894 154 uint32_t t_off = timer->MR3 - t_on;
elessair 0:f269e3021894 155 timer->MR[tid.mr] = t_off;
elessair 0:f269e3021894 156 timer->TCR = TCR_CNT_EN;
elessair 0:f269e3021894 157 }