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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 "PeripheralPins.h" // For the Peripheral to Pin Definitions found in the individual Target's Platform
#define TCR_CNT_EN 0x00000001
#define TCR_RESET 0x00000002
typedef struct {
uint8_t timer;
uint8_t mr;
} timer_mr;
static timer_mr pwm_timer_map[11] = {
{0, 0}, {0, 1}, {0, 2},
{1, 0}, {1, 1},
{2, 0}, {2, 1}, {2, 2},
{3, 0}, {3, 1}, {3, 2},
};
static LPC_CTxxBx_Type *Timers[4] = {
LPC_CT16B0, LPC_CT16B1,
LPC_CT32B0, LPC_CT32B1
};
void pwmout_init(pwmout_t* obj, PinName pin) {
// determine the channel
PWMName pwm = (PWMName)pinmap_peripheral(pin, PinMap_PWM);
MBED_ASSERT(pwm != (PWMName)NC);
obj->pwm = pwm;
// Timer registers
timer_mr tid = pwm_timer_map[pwm];
LPC_CTxxBx_Type *timer = Timers[tid.timer];
// Disable timer
timer->TCR = 0;
// Power the correspondent timer
LPC_SYSCON->SYSAHBCLKCTRL |= 1 << (tid.timer + 7);
/* Enable PWM function */
timer->PWMC = (1 << 3)|(1 << 2)|(1 << 1)|(1 << 0);
/* Reset Functionality on MR3 controlling the PWM period */
timer->MCR = 1 << 10;
// default to 20ms: standard for servos, and fine for e.g. brightness control
pwmout_period_ms(obj, 20);
pwmout_write (obj, 0);
// Wire pinout
pinmap_pinout(pin, PinMap_PWM);
}
void pwmout_free(pwmout_t* obj) {
// [TODO]
}
void pwmout_write(pwmout_t* obj, float value) {
if (value < 0.0f) {
value = 0.0;
} else if (value > 1.0f) {
value = 1.0;
}
timer_mr tid = pwm_timer_map[obj->pwm];
LPC_CTxxBx_Type *timer = Timers[tid.timer];
uint32_t t_off = timer->MR3 - (uint32_t)((float)(timer->MR3) * value);
timer->MR[tid.mr] = t_off;
}
float pwmout_read(pwmout_t* obj) {
timer_mr tid = pwm_timer_map[obj->pwm];
LPC_CTxxBx_Type *timer = Timers[tid.timer];
float v = (float)(timer->MR3 - timer->MR[tid.mr]) / (float)(timer->MR3);
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) {
int i = 0;
uint32_t period_ticks = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000);
timer_mr tid = pwm_timer_map[obj->pwm];
LPC_CTxxBx_Type *timer = Timers[tid.timer];
uint32_t old_period_ticks = timer->MR3;
// for 16bit timer, set prescaler to avoid overflow
if (timer == LPC_CT16B0 || timer == LPC_CT16B1) {
uint16_t high_period_ticks = period_ticks >> 16;
timer->PR = high_period_ticks;
period_ticks /= (high_period_ticks + 1);
}
timer->TCR = TCR_RESET;
timer->MR3 = period_ticks;
// Scale the pulse width to preserve the duty ratio
if (old_period_ticks > 0) {
for (i=0; i<3; i++) {
uint32_t t_off = period_ticks - (uint32_t)(((uint64_t)timer->MR[i] * (uint64_t)period_ticks) / (uint64_t)old_period_ticks);
timer->MR[i] = t_off;
}
}
timer->TCR = TCR_CNT_EN;
}
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) {
timer_mr tid = pwm_timer_map[obj->pwm];
LPC_CTxxBx_Type *timer = Timers[tid.timer];
uint32_t t_on = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000 / (timer->PR + 1));
timer->TCR = TCR_RESET;
if (t_on > timer->MR3) {
pwmout_period_us(obj, us);
t_on = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000 / (timer->PR + 1));
}
uint32_t t_off = timer->MR3 - t_on;
timer->MR[tid.mr] = t_off;
timer->TCR = TCR_CNT_EN;
}
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