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"
20 #include "mbed_error.h"
22 static LPC_SCT0_Type *SCTs[4] = {
23 (LPC_SCT0_Type*)LPC_SCT0,
24 (LPC_SCT0_Type*)LPC_SCT1,
25 (LPC_SCT0_Type*)LPC_SCT2,
26 (LPC_SCT0_Type*)LPC_SCT3,
29 // bit flags for used SCTs
30 static unsigned char sct_used = 0;
31 static int get_available_sct(void) {
34 if ((sct_used & (1 << i)) == 0)
40 void pwmout_init(pwmout_t* obj, PinName pin) {
41 MBED_ASSERT(pin != (uint32_t)NC);
43 int sct_n = get_available_sct();
45 error("No available SCT");
48 sct_used |= (1 << sct_n);
49 obj->pwm = SCTs[sct_n];
52 LPC_SCT0_Type* pwm = obj->pwm;
54 // Enable the SCT clock
55 LPC_SYSCON->SYSAHBCLKCTRL1 |= (1 << (obj->pwm_ch + 2));
57 // Clear peripheral reset the SCT:
58 LPC_SYSCON->PRESETCTRL1 |= (1 << (obj->pwm_ch + 2));
59 LPC_SYSCON->PRESETCTRL1 &= ~(1 << (obj->pwm_ch + 2));
64 LPC_SWM->PINASSIGN[7] &= ~0x0000FF00;
65 LPC_SWM->PINASSIGN[7] |= (pin << 8);
69 LPC_SWM->PINASSIGN[8] &= ~0x000000FF;
70 LPC_SWM->PINASSIGN[8] |= (pin);
74 LPC_SWM->PINASSIGN[8] &= ~0xFF000000;
75 LPC_SWM->PINASSIGN[8] |= (pin << 24);
79 LPC_SWM->PINASSIGN[9] &= ~0x00FF0000;
80 LPC_SWM->PINASSIGN[9] |= (pin << 16);
86 // Unified 32-bit counter, autolimit
87 pwm->CONFIG |= ((0x3 << 17) | 0x01);
89 // halt and clear the counter
90 pwm->CTRL |= (1 << 2) | (1 << 3);
92 // System Clock -> us_ticker (1)MHz
93 pwm->CTRL &= ~(0x7F << 5);
94 pwm->CTRL |= (((SystemCoreClock/1000000 - 1) & 0x7F) << 5);
96 // Match reload register
97 pwm->MATCHREL0 = 20000; // 20ms
98 pwm->MATCHREL1 = (pwm->MATCHREL0 / 4); // 50% duty
100 pwm->OUT0_SET = (1 << 0); // event 0
101 pwm->OUT0_CLR = (1 << 1); // event 1
103 pwm->EV0_CTRL = (1 << 12);
104 pwm->EV0_STATE = 0xFFFFFFFF;
105 pwm->EV1_CTRL = (1 << 12) | (1 << 0);
106 pwm->EV1_STATE = 0xFFFFFFFF;
108 // unhalt the counter:
109 // - clearing bit 2 of the CTRL register
110 pwm->CTRL &= ~(1 << 2);
112 // default to 20ms: standard for servos, and fine for e.g. brightness control
113 pwmout_period_ms(obj, 20);
114 pwmout_write (obj, 0);
117 void pwmout_free(pwmout_t* obj) {
118 // Disable the SCT clock
119 LPC_SYSCON->SYSAHBCLKCTRL1 &= ~(1 << (obj->pwm_ch + 2));
120 sct_used &= ~(1 << obj->pwm_ch);
123 void pwmout_write(pwmout_t* obj, float value) {
124 LPC_SCT0_Type* pwm = obj->pwm;
127 } else if (value > 1.0f) {
130 uint32_t t_on = (uint32_t)((float)(pwm->MATCHREL0) * value);
131 pwm->MATCHREL1 = t_on;
134 float pwmout_read(pwmout_t* obj) {
135 uint32_t t_off = obj->pwm->MATCHREL0;
136 uint32_t t_on = obj->pwm->MATCHREL1;
137 float v = (float)t_on/(float)t_off;
138 return (v > 1.0f) ? (1.0f) : (v);
141 void pwmout_period(pwmout_t* obj, float seconds) {
142 pwmout_period_us(obj, seconds * 1000000.0f);
145 void pwmout_period_ms(pwmout_t* obj, int ms) {
146 pwmout_period_us(obj, ms * 1000);
149 // Set the PWM period, keeping the duty cycle the same.
150 void pwmout_period_us(pwmout_t* obj, int us) {
151 LPC_SCT0_Type* pwm = obj->pwm;
152 uint32_t t_off = pwm->MATCHREL0;
153 uint32_t t_on = pwm->MATCHREL1;
154 float v = (float)t_on/(float)t_off;
155 pwm->MATCHREL0 = (uint32_t)us;
156 pwm->MATCHREL1 = (uint32_t)((float)us * (float)v);
159 void pwmout_pulsewidth(pwmout_t* obj, float seconds) {
160 pwmout_pulsewidth_us(obj, seconds * 1000000.0f);
163 void pwmout_pulsewidth_ms(pwmout_t* obj, int ms) {
164 pwmout_pulsewidth_us(obj, ms * 1000);
167 void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
168 obj->pwm->MATCHREL1 = (uint32_t)us;