Johannes Stratmann / mbed-dev

added prescaler for 16 bit pwm in LPC1347 target

Fork of mbed-dev by mbed official

targets/hal/TARGET_NXP/TARGET_LPC13XX/pwmout_api.c@147:ba84b7dc41a7, 2016-09-10 (annotated)

Committer:
JojoS
Date:
Sat Sep 10 15:32:04 2016 +0000
Revision:
147:ba84b7dc41a7
Parent:
144:ef7eb2e8f9f7 
added prescaler for 16 bit timers (solution as in LPC11xx), default prescaler 31 for max 28 ms period time

Who changed what in which revision?

UserRevisionLine numberNew contents of line
<> 144:ef7eb2e8f9f7 1 /* mbed Microcontroller Library
<> 144:ef7eb2e8f9f7 2 * Copyright (c) 2006-2013 ARM Limited
<> 144:ef7eb2e8f9f7 3 *
<> 144:ef7eb2e8f9f7 4 * Licensed under the Apache License, Version 2.0 (the "License");
<> 144:ef7eb2e8f9f7 5 * you may not use this file except in compliance with the License.
<> 144:ef7eb2e8f9f7 6 * You may obtain a copy of the License at
<> 144:ef7eb2e8f9f7 7 *
<> 144:ef7eb2e8f9f7 8 * http://www.apache.org/licenses/LICENSE-2.0
<> 144:ef7eb2e8f9f7 9 *
<> 144:ef7eb2e8f9f7 10 * Unless required by applicable law or agreed to in writing, software
<> 144:ef7eb2e8f9f7 11 * distributed under the License is distributed on an "AS IS" BASIS,
<> 144:ef7eb2e8f9f7 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
<> 144:ef7eb2e8f9f7 13 * See the License for the specific language governing permissions and
<> 144:ef7eb2e8f9f7 14 * limitations under the License.
<> 144:ef7eb2e8f9f7 15 */
<> 144:ef7eb2e8f9f7 16 #include "mbed_assert.h"
<> 144:ef7eb2e8f9f7 17 #include "pwmout_api.h"
<> 144:ef7eb2e8f9f7 18 #include "cmsis.h"
<> 144:ef7eb2e8f9f7 19 #include "pinmap.h"
<> 144:ef7eb2e8f9f7 20
<> 144:ef7eb2e8f9f7 21 #define TCR_CNT_EN 0x00000001
<> 144:ef7eb2e8f9f7 22 #define TCR_RESET 0x00000002
<> 144:ef7eb2e8f9f7 23
<> 144:ef7eb2e8f9f7 24 /* To have a PWM where we can change both the period and the duty cycle,
<> 144:ef7eb2e8f9f7 25 * we need an entire timer. With the following conventions:
<> 144:ef7eb2e8f9f7 26 * * MR3 is used for the PWM period
<> 144:ef7eb2e8f9f7 27 * * MR0, MR1, MR2 are used for the duty cycle
<> 144:ef7eb2e8f9f7 28 */
<> 144:ef7eb2e8f9f7 29 static const PinMap PinMap_PWM[] = {
<> 144:ef7eb2e8f9f7 30 /* CT16B0 */
<> 144:ef7eb2e8f9f7 31 {P0_8 , PWM_1, 2}, {P1_13, PWM_1, 2}, /* MR0 */
<> 144:ef7eb2e8f9f7 32 {P0_9 , PWM_2, 2}, {P1_14, PWM_2, 2}, /* MR1 */
<> 144:ef7eb2e8f9f7 33 {P0_10, PWM_3, 3}, {P1_15, PWM_3, 2}, /* MR2 */
<> 144:ef7eb2e8f9f7 34
<> 144:ef7eb2e8f9f7 35 /* CT16B1 */
<> 144:ef7eb2e8f9f7 36 {P0_21, PWM_4, 1}, /* MR0 */
<> 144:ef7eb2e8f9f7 37 {P0_22, PWM_5, 2}, {P1_23, PWM_5, 1}, /* MR1 */
<> 144:ef7eb2e8f9f7 38
<> 144:ef7eb2e8f9f7 39 /* CT32B0 */
<> 144:ef7eb2e8f9f7 40 {P0_18, PWM_6, 2}, {P1_24, PWM_6, 1}, /* MR0 */
<> 144:ef7eb2e8f9f7 41 {P0_19, PWM_7, 2}, {P1_25, PWM_7, 1}, /* MR1 */
<> 144:ef7eb2e8f9f7 42 {P0_1 , PWM_8, 2}, {P1_26, PWM_8, 1}, /* MR2 */
<> 144:ef7eb2e8f9f7 43
<> 144:ef7eb2e8f9f7 44 /* CT32B1 */
<> 144:ef7eb2e8f9f7 45 {P0_13, PWM_9 , 3}, //{P1_0, PWM_9 , 1}, /* MR0 */
<> 144:ef7eb2e8f9f7 46 {P0_14, PWM_10, 3}, //{P1_1, PWM_10, 1}, /* MR1 */
<> 144:ef7eb2e8f9f7 47 {P0_15, PWM_11, 3}, //{P1_2, PWM_11, 1}, /* MR2 */
<> 144:ef7eb2e8f9f7 48
<> 144:ef7eb2e8f9f7 49 {NC, NC, 0}
<> 144:ef7eb2e8f9f7 50 };
<> 144:ef7eb2e8f9f7 51
<> 144:ef7eb2e8f9f7 52 typedef struct {
<> 144:ef7eb2e8f9f7 53 uint8_t timer;
<> 144:ef7eb2e8f9f7 54 uint8_t mr;
<> 144:ef7eb2e8f9f7 55 } timer_mr;
<> 144:ef7eb2e8f9f7 56
<> 144:ef7eb2e8f9f7 57 static timer_mr pwm_timer_map[11] = {
<> 144:ef7eb2e8f9f7 58 {0, 0}, {0, 1}, {0, 2},
<> 144:ef7eb2e8f9f7 59 {1, 0}, {1, 1},
<> 144:ef7eb2e8f9f7 60 {2, 0}, {2, 1}, {2, 2},
<> 144:ef7eb2e8f9f7 61 {3, 0}, {3, 1}, {3, 2},
<> 144:ef7eb2e8f9f7 62 };
<> 144:ef7eb2e8f9f7 63
<> 144:ef7eb2e8f9f7 64 static LPC_CTxxBx_Type *Timers[4] = {
<> 144:ef7eb2e8f9f7 65 LPC_CT16B0, LPC_CT16B1,
<> 144:ef7eb2e8f9f7 66 LPC_CT32B0, LPC_CT32B1
<> 144:ef7eb2e8f9f7 67 };
<> 144:ef7eb2e8f9f7 68
<> 144:ef7eb2e8f9f7 69 static unsigned int pwm_clock_mhz;
<> 144:ef7eb2e8f9f7 70
<> 144:ef7eb2e8f9f7 71 void pwmout_init(pwmout_t* obj, PinName pin) {
<> 144:ef7eb2e8f9f7 72 // determine the channel
<> 144:ef7eb2e8f9f7 73 PWMName pwm = (PWMName)pinmap_peripheral(pin, PinMap_PWM);
<> 144:ef7eb2e8f9f7 74 MBED_ASSERT(pwm != (uint32_t)NC);
<> 144:ef7eb2e8f9f7 75
<> 144:ef7eb2e8f9f7 76 obj->pwm = pwm;
<> 144:ef7eb2e8f9f7 77
<> 144:ef7eb2e8f9f7 78 // Timer registers
<> 144:ef7eb2e8f9f7 79 timer_mr tid = pwm_timer_map[pwm];
<> 144:ef7eb2e8f9f7 80 LPC_CTxxBx_Type *timer = Timers[tid.timer];
<> 144:ef7eb2e8f9f7 81
<> 144:ef7eb2e8f9f7 82 // Disable timer
<> 144:ef7eb2e8f9f7 83 timer->TCR = 0;
<> 144:ef7eb2e8f9f7 84
<> 144:ef7eb2e8f9f7 85 // Power the correspondent timer
<> 144:ef7eb2e8f9f7 86 LPC_SYSCON->SYSAHBCLKCTRL |= 1 << (tid.timer + 7);
<> 144:ef7eb2e8f9f7 87
<> 144:ef7eb2e8f9f7 88 /* Enable PWM function */
<> 144:ef7eb2e8f9f7 89 timer->PWMC = (1 << 3)|(1 << 2)|(1 << 1)|(1 << 0);
<> 144:ef7eb2e8f9f7 90
<> 144:ef7eb2e8f9f7 91 /* Reset Functionality on MR3 controlling the PWM period */
<> 144:ef7eb2e8f9f7 92 timer->MCR = 1 << 10;
JojoS 147:ba84b7dc41a7 93
JojoS 147:ba84b7dc41a7 94 if (timer == LPC_CT16B0 || timer == LPC_CT16B1) {
JojoS 147:ba84b7dc41a7 95 /* Set 16-bit timer prescaler to avoid timer expire for default 20ms */
JojoS 147:ba84b7dc41a7 96 /* This can be also modified by user application, but the prescaler value */
JojoS 147:ba84b7dc41a7 97 /* might be trade-off to timer accuracy */
JojoS 147:ba84b7dc41a7 98 timer->PR = 30;
JojoS 147:ba84b7dc41a7 99 }
<> 144:ef7eb2e8f9f7 100
<> 144:ef7eb2e8f9f7 101 pwm_clock_mhz = SystemCoreClock / 1000000;
<> 144:ef7eb2e8f9f7 102
<> 144:ef7eb2e8f9f7 103 // default to 20ms: standard for servos, and fine for e.g. brightness control
<> 144:ef7eb2e8f9f7 104 pwmout_period_ms(obj, 20);
<> 144:ef7eb2e8f9f7 105 pwmout_write (obj, 0);
<> 144:ef7eb2e8f9f7 106
<> 144:ef7eb2e8f9f7 107 // Wire pinout
<> 144:ef7eb2e8f9f7 108 pinmap_pinout(pin, PinMap_PWM);
<> 144:ef7eb2e8f9f7 109 }
<> 144:ef7eb2e8f9f7 110
<> 144:ef7eb2e8f9f7 111 void pwmout_free(pwmout_t* obj) {
<> 144:ef7eb2e8f9f7 112 // [TODO]
<> 144:ef7eb2e8f9f7 113 }
<> 144:ef7eb2e8f9f7 114
<> 144:ef7eb2e8f9f7 115 void pwmout_write(pwmout_t* obj, float value) {
<> 144:ef7eb2e8f9f7 116 if (value < 0.0f) {
<> 144:ef7eb2e8f9f7 117 value = 0.0;
<> 144:ef7eb2e8f9f7 118 } else if (value > 1.0f) {
<> 144:ef7eb2e8f9f7 119 value = 1.0;
<> 144:ef7eb2e8f9f7 120 }
<> 144:ef7eb2e8f9f7 121
<> 144:ef7eb2e8f9f7 122 timer_mr tid = pwm_timer_map[obj->pwm];
<> 144:ef7eb2e8f9f7 123 LPC_CTxxBx_Type *timer = Timers[tid.timer];
<> 144:ef7eb2e8f9f7 124 uint32_t t_off = timer->MR3 - (uint32_t)((float)(timer->MR3) * value);
<> 144:ef7eb2e8f9f7 125
<> 144:ef7eb2e8f9f7 126 timer->MR[tid.mr] = t_off;
<> 144:ef7eb2e8f9f7 127 }
<> 144:ef7eb2e8f9f7 128
<> 144:ef7eb2e8f9f7 129 float pwmout_read(pwmout_t* obj) {
<> 144:ef7eb2e8f9f7 130 timer_mr tid = pwm_timer_map[obj->pwm];
<> 144:ef7eb2e8f9f7 131 LPC_CTxxBx_Type *timer = Timers[tid.timer];
<> 144:ef7eb2e8f9f7 132
<> 144:ef7eb2e8f9f7 133 float v = (float)(timer->MR3 - timer->MR[tid.mr]) / (float)(timer->MR3);
<> 144:ef7eb2e8f9f7 134 return (v > 1.0f) ? (1.0f) : (v);
<> 144:ef7eb2e8f9f7 135 }
<> 144:ef7eb2e8f9f7 136
<> 144:ef7eb2e8f9f7 137 void pwmout_period(pwmout_t* obj, float seconds) {
<> 144:ef7eb2e8f9f7 138 pwmout_period_us(obj, seconds * 1000000.0f);
<> 144:ef7eb2e8f9f7 139 }
<> 144:ef7eb2e8f9f7 140
<> 144:ef7eb2e8f9f7 141 void pwmout_period_ms(pwmout_t* obj, int ms) {
<> 144:ef7eb2e8f9f7 142 pwmout_period_us(obj, ms * 1000);
<> 144:ef7eb2e8f9f7 143 }
<> 144:ef7eb2e8f9f7 144
<> 144:ef7eb2e8f9f7 145 // Set the PWM period, keeping the duty cycle the same.
<> 144:ef7eb2e8f9f7 146 void pwmout_period_us(pwmout_t* obj, int us) {
<> 144:ef7eb2e8f9f7 147 int i = 0;
JojoS 147:ba84b7dc41a7 148 uint32_t period_ticks;
<> 144:ef7eb2e8f9f7 149
<> 144:ef7eb2e8f9f7 150 timer_mr tid = pwm_timer_map[obj->pwm];
<> 144:ef7eb2e8f9f7 151 LPC_CTxxBx_Type *timer = Timers[tid.timer];
<> 144:ef7eb2e8f9f7 152 uint32_t old_period_ticks = timer->MR3;
JojoS 147:ba84b7dc41a7 153 period_ticks = (pwm_clock_mhz * us) / (timer->PR + 1);
JojoS 147:ba84b7dc41a7 154
<> 144:ef7eb2e8f9f7 155 timer->TCR = TCR_RESET;
<> 144:ef7eb2e8f9f7 156 timer->MR3 = period_ticks;
<> 144:ef7eb2e8f9f7 157
<> 144:ef7eb2e8f9f7 158 // Scale the pulse width to preserve the duty ratio
<> 144:ef7eb2e8f9f7 159 if (old_period_ticks > 0) {
<> 144:ef7eb2e8f9f7 160 for (i=0; i<3; i++) {
<> 144:ef7eb2e8f9f7 161 uint32_t t_off = period_ticks - (uint32_t)(((uint64_t)timer->MR[i] * (uint64_t)period_ticks) / (uint64_t)old_period_ticks);
<> 144:ef7eb2e8f9f7 162 timer->MR[i] = t_off;
<> 144:ef7eb2e8f9f7 163 }
<> 144:ef7eb2e8f9f7 164 }
<> 144:ef7eb2e8f9f7 165 timer->TCR = TCR_CNT_EN;
<> 144:ef7eb2e8f9f7 166 }
<> 144:ef7eb2e8f9f7 167
<> 144:ef7eb2e8f9f7 168 void pwmout_pulsewidth(pwmout_t* obj, float seconds) {
<> 144:ef7eb2e8f9f7 169 pwmout_pulsewidth_us(obj, seconds * 1000000.0f);
<> 144:ef7eb2e8f9f7 170 }
<> 144:ef7eb2e8f9f7 171
<> 144:ef7eb2e8f9f7 172 void pwmout_pulsewidth_ms(pwmout_t* obj, int ms) {
<> 144:ef7eb2e8f9f7 173 pwmout_pulsewidth_us(obj, ms * 1000);
<> 144:ef7eb2e8f9f7 174 }
<> 144:ef7eb2e8f9f7 175
<> 144:ef7eb2e8f9f7 176 void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
<> 144:ef7eb2e8f9f7 177 timer_mr tid = pwm_timer_map[obj->pwm];
<> 144:ef7eb2e8f9f7 178 LPC_CTxxBx_Type *timer = Timers[tid.timer];
JojoS 147:ba84b7dc41a7 179 uint32_t t_on = (uint32_t)((((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000) / (timer->PR + 1)); ;
<> 144:ef7eb2e8f9f7 180
<> 144:ef7eb2e8f9f7 181 timer->TCR = TCR_RESET;
<> 144:ef7eb2e8f9f7 182 if (t_on > timer->MR3) {
<> 144:ef7eb2e8f9f7 183 pwmout_period_us(obj, us);
<> 144:ef7eb2e8f9f7 184 }
<> 144:ef7eb2e8f9f7 185 uint32_t t_off = timer->MR3 - t_on;
<> 144:ef7eb2e8f9f7 186 timer->MR[tid.mr] = t_off;
<> 144:ef7eb2e8f9f7 187 timer->TCR = TCR_CNT_EN;
<> 144:ef7eb2e8f9f7 188 }