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[] = {
33 static const uint32_t PWM_mr_offset[7] = {
34 0x18, 0x1C, 0x20, 0x24, 0x40, 0x44, 0x48
37 #define TCR_PWM_EN 0x00000008
38 static unsigned int pwm_clock_mhz;
40 void pwmout_init(pwmout_t* obj, PinName pin) {
41 // determine the channel
42 PWMName pwm = (PWMName)pinmap_peripheral(pin, PinMap_PWM);
43 MBED_ASSERT(pwm != (PWMName)NC);
48 if (obj->channel > 6) { // PWM1 is used if pwm > 6
53 obj->MR = (__IO uint32_t *)((uint32_t)obj->pwm + PWM_mr_offset[obj->channel]);
55 // ensure the power is on
56 if (obj->pwm == LPC_PWM0) {
57 LPC_SC->PCONP |= 1 << 5;
59 LPC_SC->PCONP |= 1 << 6;
62 obj->pwm->PR = 0; // no pre-scale
64 // ensure single PWM mode
65 obj->pwm->MCR = 1 << 1; // reset TC on match 0
67 // enable the specific PWM output
68 obj->pwm->PCR |= 1 << (8 + obj->channel);
70 pwm_clock_mhz = PeripheralClock / 1000000;
72 // default to 20ms: standard for servos, and fine for e.g. brightness control
73 pwmout_period_ms(obj, 20);
74 pwmout_write (obj, 0);
77 pinmap_pinout(pin, PinMap_PWM);
80 void pwmout_free(pwmout_t* obj) {
84 void pwmout_write(pwmout_t* obj, float value) {
87 } else if (value > 1.0f) {
91 // set channel match to percentage
92 uint32_t v = (uint32_t)((float)(obj->pwm->MR0) * value);
94 // workaround for PWM1[1] - Never make it equal MR0, else we get 1 cycle dropout
95 if (v == obj->pwm->MR0) {
101 // accept on next period start
102 obj->pwm->LER |= 1 << obj->channel;
105 float pwmout_read(pwmout_t* obj) {
106 float v = (float)(*obj->MR) / (float)(obj->pwm->MR0);
107 return (v > 1.0f) ? (1.0f) : (v);
110 void pwmout_period(pwmout_t* obj, float seconds) {
111 pwmout_period_us(obj, seconds * 1000000.0f);
114 void pwmout_period_ms(pwmout_t* obj, int ms) {
115 pwmout_period_us(obj, ms * 1000);
118 // Set the PWM period, keeping the duty cycle the same.
119 void pwmout_period_us(pwmout_t* obj, int us) {
120 // calculate number of ticks
121 uint32_t ticks = pwm_clock_mhz * us;
124 obj->pwm->TCR = TCR_RESET;
126 // set the global match register
127 obj->pwm->MR0 = ticks;
129 // Scale the pulse width to preserve the duty ratio
130 if (obj->pwm->MR0 > 0) {
131 *obj->MR = (*obj->MR * ticks) / obj->pwm->MR0;
134 // set the channel latch to update value at next period start
135 obj->pwm->LER |= 1 << 0;
137 // enable counter and pwm, clear reset
138 obj->pwm->TCR = TCR_CNT_EN | TCR_PWM_EN;
141 void pwmout_pulsewidth(pwmout_t* obj, float seconds) {
142 pwmout_pulsewidth_us(obj, seconds * 1000000.0f);
145 void pwmout_pulsewidth_ms(pwmout_t* obj, int ms) {
146 pwmout_pulsewidth_us(obj, ms * 1000);
149 void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
150 // calculate number of ticks
151 uint32_t v = pwm_clock_mhz * us;
153 // workaround for PWM1[1] - Never make it equal MR0, else we get 1 cycle dropout
154 if (v == obj->pwm->MR0) {
158 // set the match register value
161 // set the channel latch to update value at next period start
162 obj->pwm->LER |= 1 << obj->channel;