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/* mbed Microcontroller Library
* Copyright (c) 2006-2013 ARM Limited
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "mbed_assert.h"
#include "pwmout_api.h"
#include "cmsis.h"
#include "pinmap.h"
#include "mbed_error.h"
static LPC_SCT0_Type *SCTs[4] = {
(LPC_SCT0_Type*)LPC_SCT0,
(LPC_SCT0_Type*)LPC_SCT1,
(LPC_SCT0_Type*)LPC_SCT2,
(LPC_SCT0_Type*)LPC_SCT3,
};
// bit flags for used SCTs
static unsigned char sct_used = 0;
static int get_available_sct(void) {
int i;
for (i=0; i<4; i++) {
if ((sct_used & (1 << i)) == 0)
return i;
}
return -1;
}
void pwmout_init(pwmout_t* obj, PinName pin) {
MBED_ASSERT(pin != (uint32_t)NC);
int sct_n = get_available_sct();
if (sct_n == -1) {
error("No available SCT");
}
sct_used |= (1 << sct_n);
obj->pwm = SCTs[sct_n];
obj->pwm_ch = sct_n;
LPC_SCT0_Type* pwm = obj->pwm;
// Enable the SCT clock
LPC_SYSCON->SYSAHBCLKCTRL1 |= (1 << (obj->pwm_ch + 2));
// Clear peripheral reset the SCT:
LPC_SYSCON->PRESETCTRL1 |= (1 << (obj->pwm_ch + 2));
LPC_SYSCON->PRESETCTRL1 &= ~(1 << (obj->pwm_ch + 2));
switch(obj->pwm_ch) {
case 0:
// SCT0_OUT0
LPC_SWM->PINASSIGN[7] &= ~0x0000FF00;
LPC_SWM->PINASSIGN[7] |= (pin << 8);
break;
case 1:
// SCT1_OUT0
LPC_SWM->PINASSIGN[8] &= ~0x000000FF;
LPC_SWM->PINASSIGN[8] |= (pin);
break;
case 2:
// SCT2_OUT0
LPC_SWM->PINASSIGN[8] &= ~0xFF000000;
LPC_SWM->PINASSIGN[8] |= (pin << 24);
break;
case 3:
// SCT3_OUT0
LPC_SWM->PINASSIGN[9] &= ~0x00FF0000;
LPC_SWM->PINASSIGN[9] |= (pin << 16);
break;
default:
break;
}
// Unified 32-bit counter, autolimit
pwm->CONFIG |= ((0x3 << 17) | 0x01);
// halt and clear the counter
pwm->CTRL |= (1 << 2) | (1 << 3);
// System Clock -> us_ticker (1)MHz
pwm->CTRL &= ~(0x7F << 5);
pwm->CTRL |= (((SystemCoreClock/1000000 - 1) & 0x7F) << 5);
// Match reload register
pwm->MATCHREL0 = 20000; // 20ms
pwm->MATCHREL1 = (pwm->MATCHREL0 / 4); // 50% duty
pwm->OUT0_SET = (1 << 0); // event 0
pwm->OUT0_CLR = (1 << 1); // event 1
pwm->EV0_CTRL = (1 << 12);
pwm->EV0_STATE = 0xFFFFFFFF;
pwm->EV1_CTRL = (1 << 12) | (1 << 0);
pwm->EV1_STATE = 0xFFFFFFFF;
// unhalt the counter:
// - clearing bit 2 of the CTRL register
pwm->CTRL &= ~(1 << 2);
// default to 20ms: standard for servos, and fine for e.g. brightness control
pwmout_period_ms(obj, 20);
pwmout_write (obj, 0);
}
void pwmout_free(pwmout_t* obj) {
// Disable the SCT clock
LPC_SYSCON->SYSAHBCLKCTRL1 &= ~(1 << (obj->pwm_ch + 2));
sct_used &= ~(1 << obj->pwm_ch);
}
void pwmout_write(pwmout_t* obj, float value) {
LPC_SCT0_Type* pwm = obj->pwm;
if (value < 0.0f) {
value = 0.0;
} else if (value > 1.0f) {
value = 1.0;
}
uint32_t t_on = (uint32_t)((float)(pwm->MATCHREL0) * value);
pwm->MATCHREL1 = t_on;
}
float pwmout_read(pwmout_t* obj) {
uint32_t t_off = obj->pwm->MATCHREL0;
uint32_t t_on = obj->pwm->MATCHREL1;
float v = (float)t_on/(float)t_off;
return (v > 1.0f) ? (1.0f) : (v);
}
void pwmout_period(pwmout_t* obj, float seconds) {
pwmout_period_us(obj, seconds * 1000000.0f);
}
void pwmout_period_ms(pwmout_t* obj, int ms) {
pwmout_period_us(obj, ms * 1000);
}
// Set the PWM period, keeping the duty cycle the same.
void pwmout_period_us(pwmout_t* obj, int us) {
LPC_SCT0_Type* pwm = obj->pwm;
uint32_t t_off = pwm->MATCHREL0;
uint32_t t_on = pwm->MATCHREL1;
float v = (float)t_on/(float)t_off;
pwm->MATCHREL0 = (uint32_t)us;
pwm->MATCHREL1 = (uint32_t)((float)us * (float)v);
}
void pwmout_pulsewidth(pwmout_t* obj, float seconds) {
pwmout_pulsewidth_us(obj, seconds * 1000000.0f);
}
void pwmout_pulsewidth_ms(pwmout_t* obj, int ms) {
pwmout_pulsewidth_us(obj, ms * 1000);
}
void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
obj->pwm->MATCHREL1 = (uint32_t)us;
}
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