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Development branch of the mbed library sources. This library is kept in synch with the latest changes from the mbed SDK and it is not guaranteed to work.

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The official Mbed 2 C/C++ SDK provides the software platform and libraries to build your applications.

Last commit 20 Feb 2019 by mbed official

targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/pwmout_api.c@32:4742f6c694e8, 2013-09-30 (annotated)

Committer:
mbed_official
Date:
Mon Sep 30 20:45:04 2013 +0100
Revision:
32:4742f6c694e8
Parent:
targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/TARGET_LPC11XX/pwmout_api.c@30:91c1d09ada54 
Synchronized with git revision e8afb9cd1deecf3a0ef2c140d38e3f2d68a2eb50

Who changed what in which revision?

UserRevisionLine numberNew contents of line
mbed_official 30:91c1d09ada54 1 /* mbed Microcontroller Library
mbed_official 30:91c1d09ada54 2 * Copyright (c) 2006-2013 ARM Limited
mbed_official 30:91c1d09ada54 3 *
mbed_official 30:91c1d09ada54 4 * Licensed under the Apache License, Version 2.0 (the "License");
mbed_official 30:91c1d09ada54 5 * you may not use this file except in compliance with the License.
mbed_official 30:91c1d09ada54 6 * You may obtain a copy of the License at
mbed_official 30:91c1d09ada54 7 *
mbed_official 30:91c1d09ada54 8 * http://www.apache.org/licenses/LICENSE-2.0
mbed_official 30:91c1d09ada54 9 *
mbed_official 30:91c1d09ada54 10 * Unless required by applicable law or agreed to in writing, software
mbed_official 30:91c1d09ada54 11 * distributed under the License is distributed on an "AS IS" BASIS,
mbed_official 30:91c1d09ada54 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
mbed_official 30:91c1d09ada54 13 * See the License for the specific language governing permissions and
mbed_official 30:91c1d09ada54 14 * limitations under the License.
mbed_official 30:91c1d09ada54 15 */
mbed_official 30:91c1d09ada54 16 #include "pwmout_api.h"
mbed_official 30:91c1d09ada54 17 #include "cmsis.h"
mbed_official 30:91c1d09ada54 18 #include "pinmap.h"
mbed_official 30:91c1d09ada54 19 #include "error.h"
mbed_official 30:91c1d09ada54 20
mbed_official 30:91c1d09ada54 21 #define TCR_CNT_EN 0x00000001
mbed_official 30:91c1d09ada54 22 #define TCR_RESET 0x00000002
mbed_official 30:91c1d09ada54 23
mbed_official 30:91c1d09ada54 24 /* To have a PWM where we can change both the period and the duty cycle,
mbed_official 30:91c1d09ada54 25 * we need an entire timer. With the following conventions:
mbed_official 30:91c1d09ada54 26 * * MR3 is used for the PWM period
mbed_official 30:91c1d09ada54 27 * * MR0, MR1, MR2 are used for the duty cycle
mbed_official 30:91c1d09ada54 28 */
mbed_official 30:91c1d09ada54 29 static const PinMap PinMap_PWM[] = {
mbed_official 30:91c1d09ada54 30 /* CT16B0 */
mbed_official 30:91c1d09ada54 31 {P0_8 , PWM_1, 0x02}, /* MR0 */
mbed_official 30:91c1d09ada54 32 {P0_9 , PWM_2, 0x02}, /* MR1 */
mbed_official 30:91c1d09ada54 33
mbed_official 30:91c1d09ada54 34 /* CT16B1 */
mbed_official 30:91c1d09ada54 35 {P1_9 , PWM_3, 0x01}, /* MR0 */
mbed_official 30:91c1d09ada54 36 {P1_10, PWM_4, 0x02}, /* MR1 */
mbed_official 30:91c1d09ada54 37
mbed_official 30:91c1d09ada54 38 /* CT32B0 */
mbed_official 30:91c1d09ada54 39 {P0_1 , PWM_5, 0x02}, /* MR2 */
mbed_official 30:91c1d09ada54 40
mbed_official 30:91c1d09ada54 41 {NC , NC ,0x00}
mbed_official 30:91c1d09ada54 42 };
mbed_official 30:91c1d09ada54 43
mbed_official 30:91c1d09ada54 44 typedef struct {
mbed_official 30:91c1d09ada54 45 uint8_t timer;
mbed_official 30:91c1d09ada54 46 uint8_t mr;
mbed_official 30:91c1d09ada54 47 } timer_mr;
mbed_official 30:91c1d09ada54 48
mbed_official 30:91c1d09ada54 49 static timer_mr pwm_timer_map[5] = {
mbed_official 30:91c1d09ada54 50 {0, 0}, /* CT16B0, MR0 */
mbed_official 30:91c1d09ada54 51 {0, 1}, /* CT16B0, MR1 */
mbed_official 30:91c1d09ada54 52
mbed_official 30:91c1d09ada54 53 {1, 0}, /* CT16B1, MR0 */
mbed_official 30:91c1d09ada54 54 {1, 1}, /* CT16B1, MR1 */
mbed_official 30:91c1d09ada54 55
mbed_official 30:91c1d09ada54 56 {2, 2}, /* CT32B0, MR2 */
mbed_official 30:91c1d09ada54 57 };
mbed_official 30:91c1d09ada54 58
mbed_official 30:91c1d09ada54 59 static LPC_TMR_TypeDef *Timers[3] = {
mbed_official 30:91c1d09ada54 60 LPC_TMR16B0, LPC_TMR16B1,
mbed_official 30:91c1d09ada54 61 LPC_TMR32B0
mbed_official 30:91c1d09ada54 62 };
mbed_official 30:91c1d09ada54 63
mbed_official 30:91c1d09ada54 64 void pwmout_init(pwmout_t* obj, PinName pin) {
mbed_official 30:91c1d09ada54 65 // determine the channel
mbed_official 30:91c1d09ada54 66 PWMName pwm = (PWMName)pinmap_peripheral(pin, PinMap_PWM);
mbed_official 30:91c1d09ada54 67 if (pwm == (uint32_t)NC)
mbed_official 30:91c1d09ada54 68 error("PwmOut pin mapping failed");
mbed_official 30:91c1d09ada54 69
mbed_official 30:91c1d09ada54 70 obj->pwm = pwm;
mbed_official 30:91c1d09ada54 71
mbed_official 30:91c1d09ada54 72 // Timer registers
mbed_official 30:91c1d09ada54 73 timer_mr tid = pwm_timer_map[pwm];
mbed_official 30:91c1d09ada54 74 LPC_TMR_TypeDef *timer = Timers[tid.timer];
mbed_official 30:91c1d09ada54 75
mbed_official 30:91c1d09ada54 76 // Disable timer
mbed_official 30:91c1d09ada54 77 timer->TCR = 0;
mbed_official 30:91c1d09ada54 78
mbed_official 30:91c1d09ada54 79 // Power the correspondent timer
mbed_official 30:91c1d09ada54 80 LPC_SYSCON->SYSAHBCLKCTRL |= 1 << (tid.timer + 7);
mbed_official 30:91c1d09ada54 81
mbed_official 30:91c1d09ada54 82 /* Enable PWM function */
mbed_official 30:91c1d09ada54 83 timer->PWMC = (1 << 3)|(1 << 2)|(1 << 1)|(1 << 0);
mbed_official 30:91c1d09ada54 84
mbed_official 30:91c1d09ada54 85 /* Reset Functionality on MR3 controlling the PWM period */
mbed_official 30:91c1d09ada54 86 timer->MCR = 1 << 10;
mbed_official 30:91c1d09ada54 87
mbed_official 30:91c1d09ada54 88 if (timer == LPC_TMR16B0 || timer == LPC_TMR16B1) {
mbed_official 30:91c1d09ada54 89 /* Set 16-bit timer prescaler to avoid timer expire for default 20ms */
mbed_official 30:91c1d09ada54 90 /* This can be also modified by user application, but the prescaler value */
mbed_official 30:91c1d09ada54 91 /* might be trade-off to timer accuracy */
mbed_official 30:91c1d09ada54 92 timer->PR = 30;
mbed_official 30:91c1d09ada54 93 }
mbed_official 30:91c1d09ada54 94
mbed_official 30:91c1d09ada54 95 // default to 20ms: standard for servos, and fine for e.g. brightness control
mbed_official 30:91c1d09ada54 96 pwmout_period_ms(obj, 20);
mbed_official 30:91c1d09ada54 97 pwmout_write (obj, 0);
mbed_official 30:91c1d09ada54 98
mbed_official 30:91c1d09ada54 99 // Wire pinout
mbed_official 30:91c1d09ada54 100 pinmap_pinout(pin, PinMap_PWM);
mbed_official 30:91c1d09ada54 101 }
mbed_official 30:91c1d09ada54 102
mbed_official 30:91c1d09ada54 103 void pwmout_free(pwmout_t* obj) {
mbed_official 30:91c1d09ada54 104 // [TODO]
mbed_official 30:91c1d09ada54 105 }
mbed_official 30:91c1d09ada54 106
mbed_official 30:91c1d09ada54 107 void pwmout_write(pwmout_t* obj, float value) {
mbed_official 30:91c1d09ada54 108 if (value < 0.0f) {
mbed_official 30:91c1d09ada54 109 value = 0.0;
mbed_official 30:91c1d09ada54 110 } else if (value > 1.0f) {
mbed_official 30:91c1d09ada54 111 value = 1.0;
mbed_official 30:91c1d09ada54 112 }
mbed_official 30:91c1d09ada54 113
mbed_official 30:91c1d09ada54 114 timer_mr tid = pwm_timer_map[obj->pwm];
mbed_official 30:91c1d09ada54 115 LPC_TMR_TypeDef *timer = Timers[tid.timer];
mbed_official 30:91c1d09ada54 116 uint32_t t_off = timer->MR3 - (uint32_t)((float)(timer->MR3) * value);
mbed_official 30:91c1d09ada54 117
mbed_official 30:91c1d09ada54 118 timer->TCR = TCR_RESET;
mbed_official 30:91c1d09ada54 119 timer->MR[tid.mr] = t_off;
mbed_official 30:91c1d09ada54 120 timer->TCR = TCR_CNT_EN;
mbed_official 30:91c1d09ada54 121 }
mbed_official 30:91c1d09ada54 122
mbed_official 30:91c1d09ada54 123 float pwmout_read(pwmout_t* obj) {
mbed_official 30:91c1d09ada54 124 timer_mr tid = pwm_timer_map[obj->pwm];
mbed_official 30:91c1d09ada54 125 LPC_TMR_TypeDef *timer = Timers[tid.timer];
mbed_official 30:91c1d09ada54 126
mbed_official 30:91c1d09ada54 127 float v = (float)(timer->MR3 - timer->MR[tid.mr]) / (float)(timer->MR3);
mbed_official 30:91c1d09ada54 128 return (v > 1.0f) ? (1.0f) : (v);
mbed_official 30:91c1d09ada54 129 }
mbed_official 30:91c1d09ada54 130
mbed_official 30:91c1d09ada54 131 void pwmout_period(pwmout_t* obj, float seconds) {
mbed_official 30:91c1d09ada54 132 pwmout_period_us(obj, seconds * 1000000.0f);
mbed_official 30:91c1d09ada54 133 }
mbed_official 30:91c1d09ada54 134
mbed_official 30:91c1d09ada54 135 void pwmout_period_ms(pwmout_t* obj, int ms) {
mbed_official 30:91c1d09ada54 136 pwmout_period_us(obj, ms * 1000);
mbed_official 30:91c1d09ada54 137 }
mbed_official 30:91c1d09ada54 138
mbed_official 30:91c1d09ada54 139 // Set the PWM period, keeping the duty cycle the same.
mbed_official 30:91c1d09ada54 140 void pwmout_period_us(pwmout_t* obj, int us) {
mbed_official 30:91c1d09ada54 141 int i = 0;
mbed_official 30:91c1d09ada54 142 uint32_t period_ticks;
mbed_official 30:91c1d09ada54 143
mbed_official 30:91c1d09ada54 144 timer_mr tid = pwm_timer_map[obj->pwm];
mbed_official 30:91c1d09ada54 145 LPC_TMR_TypeDef *timer = Timers[tid.timer];
mbed_official 30:91c1d09ada54 146 uint32_t old_period_ticks = timer->MR3;
mbed_official 30:91c1d09ada54 147 period_ticks = (SystemCoreClock / 1000000 * us) / (timer->PR + 1);
mbed_official 30:91c1d09ada54 148
mbed_official 30:91c1d09ada54 149 timer->TCR = TCR_RESET;
mbed_official 30:91c1d09ada54 150 timer->MR3 = period_ticks;
mbed_official 30:91c1d09ada54 151
mbed_official 30:91c1d09ada54 152 // Scale the pulse width to preserve the duty ratio
mbed_official 30:91c1d09ada54 153 if (old_period_ticks > 0) {
mbed_official 30:91c1d09ada54 154 for (i=0; i<3; i++) {
mbed_official 30:91c1d09ada54 155 uint32_t t_off = period_ticks - (uint32_t)(((uint64_t)timer->MR[i] * (uint64_t)period_ticks) / (uint64_t)old_period_ticks);
mbed_official 30:91c1d09ada54 156 timer->MR[i] = t_off;
mbed_official 30:91c1d09ada54 157 }
mbed_official 30:91c1d09ada54 158 }
mbed_official 30:91c1d09ada54 159 timer->TCR = TCR_CNT_EN;
mbed_official 30:91c1d09ada54 160 }
mbed_official 30:91c1d09ada54 161
mbed_official 30:91c1d09ada54 162 void pwmout_pulsewidth(pwmout_t* obj, float seconds) {
mbed_official 30:91c1d09ada54 163 pwmout_pulsewidth_us(obj, seconds * 1000000.0f);
mbed_official 30:91c1d09ada54 164 }
mbed_official 30:91c1d09ada54 165
mbed_official 30:91c1d09ada54 166 void pwmout_pulsewidth_ms(pwmout_t* obj, int ms) {
mbed_official 30:91c1d09ada54 167 pwmout_pulsewidth_us(obj, ms * 1000);
mbed_official 30:91c1d09ada54 168 }
mbed_official 30:91c1d09ada54 169
mbed_official 30:91c1d09ada54 170 void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
mbed_official 30:91c1d09ada54 171 timer_mr tid = pwm_timer_map[obj->pwm];
mbed_official 30:91c1d09ada54 172 LPC_TMR_TypeDef *timer = Timers[tid.timer];
mbed_official 30:91c1d09ada54 173 uint32_t t_on = (uint32_t)((((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000) / (timer->PR + 1));
mbed_official 30:91c1d09ada54 174
mbed_official 30:91c1d09ada54 175 timer->TCR = TCR_RESET;
mbed_official 30:91c1d09ada54 176 if (t_on > timer->MR3) {
mbed_official 30:91c1d09ada54 177 pwmout_period_us(obj, us);
mbed_official 30:91c1d09ada54 178 }
mbed_official 30:91c1d09ada54 179 uint32_t t_off = timer->MR3 - t_on;
mbed_official 30:91c1d09ada54 180 timer->MR[tid.mr] = t_off;
mbed_official 30:91c1d09ada54 181 timer->TCR = TCR_CNT_EN;
mbed_official 30:91c1d09ada54 182 }