1 /* mbed Microcontroller Library
2 * Copyright (c) 2006-2013 ARM Limited
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
8 * http://www.apache.org/licenses/LICENSE-2.0
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.
16 #include "mbed_assert.h"
17 #include "pwmout_api.h"
21 #define TCR_CNT_EN 0x00000001
22 #define TCR_RESET 0x00000002
24 // PORT ID, PWM ID, Pin function
25 static const PinMap PinMap_PWM[] = {
59 static const uint32_t PWM_mr_offset[7] = {
60 0x18, 0x1C, 0x20, 0x24, 0x40, 0x44, 0x48
63 #define TCR_PWM_EN 0x00000008
64 static unsigned int pwm_clock_mhz;
66 void pwmout_init(pwmout_t* obj, PinName pin) {
67 // determine the channel
68 PWMName pwm = (PWMName)pinmap_peripheral(pin, PinMap_PWM);
69 MBED_ASSERT(pwm != (PWMName)NC);
74 if (obj->channel > 6) { // PWM1 is used if pwm > 6
79 obj->MR = (__IO uint32_t *)((uint32_t)obj->pwm + PWM_mr_offset[obj->channel]);
81 // ensure the power is on
82 if (obj->pwm == LPC_PWM0) {
83 LPC_SC->PCONP |= 1 << 5;
85 LPC_SC->PCONP |= 1 << 6;
88 obj->pwm->PR = 0; // no pre-scale
90 // ensure single PWM mode
91 obj->pwm->MCR = 1 << 1; // reset TC on match 0
93 // enable the specific PWM output
94 obj->pwm->PCR |= 1 << (8 + obj->channel);
96 pwm_clock_mhz = PeripheralClock / 1000000;
98 // default to 20ms: standard for servos, and fine for e.g. brightness control
99 pwmout_period_ms(obj, 20);
100 pwmout_write (obj, 0);
103 pinmap_pinout(pin, PinMap_PWM);
106 void pwmout_free(pwmout_t* obj) {
110 void pwmout_write(pwmout_t* obj, float value) {
113 } else if (value > 1.0f) {
117 // set channel match to percentage
118 uint32_t v = (uint32_t)((float)(obj->pwm->MR0) * value);
120 // workaround for PWM1[1] - Never make it equal MR0, else we get 1 cycle dropout
121 if (v == obj->pwm->MR0) {
127 // accept on next period start
128 obj->pwm->LER |= 1 << obj->channel;
131 float pwmout_read(pwmout_t* obj) {
132 float v = (float)(*obj->MR) / (float)(obj->pwm->MR0);
133 return (v > 1.0f) ? (1.0f) : (v);
136 void pwmout_period(pwmout_t* obj, float seconds) {
137 pwmout_period_us(obj, seconds * 1000000.0f);
140 void pwmout_period_ms(pwmout_t* obj, int ms) {
141 pwmout_period_us(obj, ms * 1000);
144 // Set the PWM period, keeping the duty cycle the same.
145 void pwmout_period_us(pwmout_t* obj, int us) {
146 // calculate number of ticks
147 uint32_t ticks = pwm_clock_mhz * us;
150 obj->pwm->TCR = TCR_RESET;
152 // set the global match register
153 obj->pwm->MR0 = ticks;
155 // Scale the pulse width to preserve the duty ratio
156 if (obj->pwm->MR0 > 0) {
157 *obj->MR = (*obj->MR * ticks) / obj->pwm->MR0;
160 // set the channel latch to update value at next period start
161 obj->pwm->LER |= 1 << 0;
163 // enable counter and pwm, clear reset
164 obj->pwm->TCR = TCR_CNT_EN | TCR_PWM_EN;
167 void pwmout_pulsewidth(pwmout_t* obj, float seconds) {
168 pwmout_pulsewidth_us(obj, seconds * 1000000.0f);
171 void pwmout_pulsewidth_ms(pwmout_t* obj, int ms) {
172 pwmout_pulsewidth_us(obj, ms * 1000);
175 void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
176 // calculate number of ticks
177 uint32_t v = pwm_clock_mhz * us;
179 // workaround for PWM1[1] - Never make it equal MR0, else we get 1 cycle dropout
180 if (v == obj->pwm->MR0) {
184 // set the match register value
187 // set the channel latch to update value at next period start
188 obj->pwm->LER |= 1 << obj->channel;