mbed library sources
Dependents: frdm_kl05z_gpio_test
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Diff: targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/pwmout_api.c
- Revision:
- 32:4742f6c694e8
- Parent:
- 30:91c1d09ada54
- Child:
- 227:7bd0639b8911
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/targets/hal/TARGET_NXP/TARGET_LPC11XX_11CXX/pwmout_api.c Mon Sep 30 20:45:04 2013 +0100 @@ -0,0 +1,182 @@ +/* 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 "error.h" + +#define TCR_CNT_EN 0x00000001 +#define TCR_RESET 0x00000002 + +/* To have a PWM where we can change both the period and the duty cycle, + * we need an entire timer. With the following conventions: + * * MR3 is used for the PWM period + * * MR0, MR1, MR2 are used for the duty cycle + */ +static const PinMap PinMap_PWM[] = { + /* CT16B0 */ + {P0_8 , PWM_1, 0x02}, /* MR0 */ + {P0_9 , PWM_2, 0x02}, /* MR1 */ + + /* CT16B1 */ + {P1_9 , PWM_3, 0x01}, /* MR0 */ + {P1_10, PWM_4, 0x02}, /* MR1 */ + + /* CT32B0 */ + {P0_1 , PWM_5, 0x02}, /* MR2 */ + + {NC , NC ,0x00} +}; + +typedef struct { + uint8_t timer; + uint8_t mr; +} timer_mr; + +static timer_mr pwm_timer_map[5] = { + {0, 0}, /* CT16B0, MR0 */ + {0, 1}, /* CT16B0, MR1 */ + + {1, 0}, /* CT16B1, MR0 */ + {1, 1}, /* CT16B1, MR1 */ + + {2, 2}, /* CT32B0, MR2 */ +}; + +static LPC_TMR_TypeDef *Timers[3] = { + LPC_TMR16B0, LPC_TMR16B1, + LPC_TMR32B0 +}; + +void pwmout_init(pwmout_t* obj, PinName pin) { + // determine the channel + PWMName pwm = (PWMName)pinmap_peripheral(pin, PinMap_PWM); + if (pwm == (uint32_t)NC) + error("PwmOut pin mapping failed"); + + obj->pwm = pwm; + + // Timer registers + timer_mr tid = pwm_timer_map[pwm]; + LPC_TMR_TypeDef *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; + + if (timer == LPC_TMR16B0 || timer == LPC_TMR16B1) { + /* Set 16-bit timer prescaler to avoid timer expire for default 20ms */ + /* This can be also modified by user application, but the prescaler value */ + /* might be trade-off to timer accuracy */ + timer->PR = 30; + } + + // 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_TMR_TypeDef *timer = Timers[tid.timer]; + uint32_t t_off = timer->MR3 - (uint32_t)((float)(timer->MR3) * value); + + timer->TCR = TCR_RESET; + timer->MR[tid.mr] = t_off; + timer->TCR = TCR_CNT_EN; +} + +float pwmout_read(pwmout_t* obj) { + timer_mr tid = pwm_timer_map[obj->pwm]; + LPC_TMR_TypeDef *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; + + timer_mr tid = pwm_timer_map[obj->pwm]; + LPC_TMR_TypeDef *timer = Timers[tid.timer]; + uint32_t old_period_ticks = timer->MR3; + period_ticks = (SystemCoreClock / 1000000 * us) / (timer->PR + 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_TMR_TypeDef *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); + } + uint32_t t_off = timer->MR3 - t_on; + timer->MR[tid.mr] = t_off; + timer->TCR = TCR_CNT_EN; +}