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Superseded
This library was superseded by mbed-dev - https://os.mbed.com/users/mbed_official/code/mbed-dev/.
Development branch of the mbed library sources. This library is kept in synch with the latest changes from the mbed SDK and it is not guaranteed to work.
If you are looking for a stable and tested release, please import one of the official mbed library releases:
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The official Mbed 2 C/C++ SDK provides the software platform and libraries to build your applications.
targets/hal/TARGET_NXP/TARGET_LPC176X/pwmout_api.c
- Committer:
- mbed_official
- Date:
- 2014-12-16
- Revision:
- 440:8a0b45cd594f
- Parent:
- 227:7bd0639b8911
File content as of revision 440:8a0b45cd594f:
/* 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; }