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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"
#define TCR_CNT_EN 0x00000001
#define TCR_RESET 0x00000002
// PORT ID, PWM ID, Pin function
static const PinMap PinMap_PWM[] = {
{P1_18, PWM_1, 2},
{P1_20, PWM_2, 2},
{P1_21, PWM_3, 2},
{P1_23, PWM_4, 2},
{P1_24, PWM_5, 2},
{P1_26, PWM_6, 2},
{P2_0 , PWM_1, 1},
{P2_1 , PWM_2, 1},
{P2_2 , PWM_3, 1},
{P2_3 , PWM_4, 1},
{P2_4 , PWM_5, 1},
{P2_5 , PWM_6, 1},
{P3_25, PWM_2, 3},
{P3_26, PWM_3, 3},
{NC, NC, 0}
};
__IO uint32_t *PWM_MATCH[] = {
&(LPC_PWM1->MR0),
&(LPC_PWM1->MR1),
&(LPC_PWM1->MR2),
&(LPC_PWM1->MR3),
&(LPC_PWM1->MR4),
&(LPC_PWM1->MR5),
&(LPC_PWM1->MR6)
};
#define TCR_PWM_EN 0x00000008
static unsigned int pwm_clock_mhz;
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;
obj->MR = PWM_MATCH[pwm];
// ensure the power is on
LPC_SC->PCONP |= 1 << 6;
// ensure clock to /4
LPC_SC->PCLKSEL0 &= ~(0x3 << 12); // pclk = /4
LPC_PWM1->PR = 0; // no pre-scale
// ensure single PWM mode
LPC_PWM1->MCR = 1 << 1; // reset TC on match 0
// enable the specific PWM output
LPC_PWM1->PCR |= 1 << (8 + pwm);
pwm_clock_mhz = SystemCoreClock / 4000000;
// 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;
}
// set channel match to percentage
uint32_t v = (uint32_t)((float)(LPC_PWM1->MR0) * value);
// workaround for PWM1[1] - Never make it equal MR0, else we get 1 cycle dropout
if (v == LPC_PWM1->MR0) {
v++;
}
*obj->MR = v;
// accept on next period start
LPC_PWM1->LER |= 1 << obj->pwm;
}
float pwmout_read(pwmout_t* obj) {
float v = (float)(*obj->MR) / (float)(LPC_PWM1->MR0);
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) {
// calculate number of ticks
uint32_t ticks = pwm_clock_mhz * us;
// set reset
LPC_PWM1->TCR = TCR_RESET;
// set the global match register
LPC_PWM1->MR0 = ticks;
// Scale the pulse width to preserve the duty ratio
if (LPC_PWM1->MR0 > 0) {
*obj->MR = (*obj->MR * ticks) / LPC_PWM1->MR0;
}
// set the channel latch to update value at next period start
LPC_PWM1->LER |= 1 << 0;
// enable counter and pwm, clear reset
LPC_PWM1->TCR = TCR_CNT_EN | TCR_PWM_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) {
// calculate number of ticks
uint32_t v = pwm_clock_mhz * us;
// workaround for PWM1[1] - Never make it equal MR0, else we get 1 cycle dropout
if (v == LPC_PWM1->MR0) {
v++;
}
// set the match register value
*obj->MR = v;
// set the channel latch to update value at next period start
LPC_PWM1->LER |= 1 << obj->pwm;
}
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