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mbed-os/targets/TARGET_NXP/TARGET_LPC11U6X/pwmout_api.c

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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 "pwmout_api.h"
#include "cmsis.h"
#include "pinmap.h"
#include "mbed_error.h"
#if DEVICE_PWMOUT
#define SCT_CHANNELS 2
static const PinMap PinMap_PWM[] = {
{P1_19, SCT0_0, 2},
{P2_2 , SCT0_1, 3},
{P2_7 , SCT0_2, 2},
{P1_13, SCT0_3, 2},
{P2_16, SCT1_0, 1},
{P2_17, SCT1_1, 1},
{P2_18, SCT1_2, 1},
{P2_19, SCT1_3, 1},
{NC , NC ,0}
};
static LPC_SCT0_Type *SCTs[SCT_CHANNELS] = {
(LPC_SCT0_Type*)LPC_SCT0,
(LPC_SCT0_Type*)LPC_SCT1,
};
// bit flags for used SCTs
static unsigned char sct_used = 0;
static int get_available_sct(void) {
int i;
for (i=0; i<SCT_CHANNELS; i++) {
if ((sct_used & (1 << i)) == 0)
return i;
}
return -1;
}
void pwmout_init(pwmout_t* obj, PinName pin) {
// determine the SPI to use
PWMName pwm_mapped = (PWMName)pinmap_peripheral(pin, PinMap_PWM);
if (pwm_mapped == (PWMName)NC) {
error("PwmOut pin mapping failed");
}
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;
// Enable the SCT clock
LPC_SYSCON->SYSAHBCLKCTRL |= (1UL << 31);
// Clear peripheral reset the SCT:
LPC_SYSCON->PRESETCTRL |= (1 << (obj->pwm_ch + 9));
pinmap_pinout(pin, PinMap_PWM);
LPC_SCT0_Type* pwm = obj->pwm;
// Unified 32-bit counter, autolimit
pwm->CONFIG |= ((0x3 << 17) | 0x01);
// halt and clear the counter
pwm->CTRL |= (1 << 2) | (1 << 3);
switch(pwm_mapped) {
case SCT0_0:
case SCT1_0:
pwm->OUT0_SET = (1 << 0); // event 0
pwm->OUT0_CLR = (1 << 1); // event 1
break;
case SCT0_1:
case SCT1_1:
pwm->OUT1_SET = (1 << 0); // event 0
pwm->OUT1_CLR = (1 << 1); // event 1
break;
case SCT0_2:
case SCT1_2:
pwm->OUT2_SET = (1 << 0); // event 0
pwm->OUT2_CLR = (1 << 1); // event 1
break;
case SCT0_3:
case SCT1_3:
pwm->OUT3_SET = (1 << 0); // event 0
pwm->OUT3_CLR = (1 << 1); // event 1
break;
default:
break;
}
// Event 0 : MATCH and MATCHSEL=0
pwm->EV0_CTRL = (1 << 12);
pwm->EV0_STATE = 0xFFFFFFFF;
// Event 1 : MATCH and MATCHSEL=1
pwm->EV1_CTRL = (1 << 12) | (1 << 0);
pwm->EV1_STATE = 0xFFFFFFFF;
// 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) {
sct_used &= ~(1 << obj->pwm_ch);
if (sct_used == 0) {
// Disable the SCT clock
LPC_SYSCON->SYSAHBCLKCTRL &= ~(1UL << 31);
}
}
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 + 1) * value);
if (t_on > 0) {
pwm->MATCHREL1 = t_on - 1;
// Un-halt the timer and ensure the new pulse-width takes immediate effect if necessary
if (pwm->CTRL & (1 << 2)) {
pwm->MATCH1 = pwm->MATCHREL1;
pwm->CTRL &= ~(1 << 2);
}
} else {
// Halt the timer and force the output low
pwm->CTRL |= (1 << 2) | (1 << 3);
pwm->OUTPUT = 0x00000000;
}
}
float pwmout_read(pwmout_t* obj) {
LPC_SCT0_Type* pwm = obj->pwm;
uint32_t t_off = pwm->MATCHREL0 + 1;
uint32_t t_on = (!(pwm->CTRL & (1 << 2))) ? pwm->MATCHREL1 + 1 : 0;
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 + 1;
uint32_t t_on = (!(pwm->CTRL & (1 << 2))) ? pwm->MATCHREL1 + 1 : 0;
float v = (float)t_on/(float)t_off;
uint32_t period_ticks = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000);
uint32_t pulsewidth_ticks = period_ticks * v;
pwm->MATCHREL0 = period_ticks - 1;
if (pulsewidth_ticks > 0) {
pwm->MATCHREL1 = pulsewidth_ticks - 1;
// Un-halt the timer and ensure the new period & pulse-width take immediate effect if necessary
if (pwm->CTRL & (1 << 2)) {
pwm->MATCH0 = pwm->MATCHREL0;
pwm->MATCH1 = pwm->MATCHREL1;
pwm->CTRL &= ~(1 << 2);
}
} else {
// Halt the timer and force the output low
pwm->CTRL |= (1 << 2) | (1 << 3);
pwm->OUTPUT = 0x00000000;
// Ensure the new period will take immediate effect when the timer is un-halted
pwm->MATCH0 = pwm->MATCHREL0;
}
}
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) {
LPC_SCT0_Type* pwm = obj->pwm;
if (us > 0) {
pwm->MATCHREL1 = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000) - 1;
// Un-halt the timer and ensure the new pulse-width takes immediate effect if necessary
if (pwm->CTRL & (1 << 2)) {
pwm->MATCH1 = pwm->MATCHREL1;
pwm->CTRL &= ~(1 << 2);
}
} else {
// Halt the timer and force the output low
pwm->CTRL |= (1 << 2) | (1 << 3);
pwm->OUTPUT = 0x00000000;
}
}
#endif
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