pwmout_api.c

00001 /* mbed Microcontroller Library
00002  * Copyright (c) 2006-2013 ARM Limited
00003  *
00004  * Licensed under the Apache License, Version 2.0 (the "License");
00005  * you may not use this file except in compliance with the License.
00006  * You may obtain a copy of the License at
00007  *
00008  *     http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 #include "pwmout_api.h"
00017 #include "cmsis.h"
00018 #include "pinmap.h"
00019 #include "error.h"
00020 
00021 #define TCR_CNT_EN       0x00000001
00022 #define TCR_RESET        0x00000002
00023 
00024 //  PORT ID, PWM ID, Pin function
00025 static const PinMap PinMap_PWM[] = {
00026     {P1_2,  PWM0_1, 3},
00027     {P1_3,  PWM0_2, 3},
00028     {P1_5,  PWM0_3, 3},
00029     {P1_6,  PWM0_4, 3},
00030     {P1_7,  PWM0_5, 3},
00031     {P1_11, PWM0_6, 3},
00032     {P1_18, PWM1_1, 2},
00033     {P1_20, PWM1_2, 2},
00034     {P1_21, PWM1_3, 2},
00035     {P1_23, PWM1_4, 2},
00036     {P1_24, PWM1_5, 2},
00037     {P1_26, PWM1_6, 2},
00038     {P2_0,  PWM1_1, 1},
00039     {P2_1,  PWM1_2, 1},
00040     {P2_2,  PWM1_3, 1},
00041     {P2_3,  PWM1_4, 1},
00042     {P2_4,  PWM1_5, 1},
00043     {P2_5,  PWM1_6, 1},
00044     {P3_16, PWM0_1, 2},
00045     {P3_17, PWM0_2, 2},
00046     {P3_18, PWM0_3, 2},
00047     {P3_19, PWM0_4, 2},
00048     {P3_20, PWM0_5, 2},
00049     {P3_21, PWM0_6, 2},
00050     {P3_24, PWM1_1, 2},
00051     {P3_25, PWM1_2, 2},
00052     {P3_26, PWM1_3, 2},
00053     {P3_27, PWM1_4, 2},
00054     {P3_28, PWM1_5, 2},
00055     {P3_29, PWM1_6, 2},
00056     {NC, NC, 0}
00057 };
00058 
00059 static const uint32_t PWM_mr_offset[7] = {
00060     0x18, 0x1C, 0x20, 0x24, 0x40, 0x44, 0x48
00061 };
00062 
00063 #define TCR_PWM_EN       0x00000008
00064 static unsigned int pwm_clock_mhz;
00065 
00066 void pwmout_init(pwmout_t* obj, PinName pin) {
00067     // determine the channel
00068     PWMName pwm = (PWMName)pinmap_peripheral(pin, PinMap_PWM);
00069     if (pwm == (uint32_t)NC)
00070         error("PwmOut pin mapping failed");
00071     
00072     obj->channel = pwm;
00073     obj->pwm = LPC_PWM0;
00074     
00075     if (obj->channel > 6) { // PWM1 is used if pwm > 6
00076       obj->channel -= 6;
00077       obj->pwm = LPC_PWM1;
00078     }
00079     
00080     obj->MR = (__IO uint32_t *)((uint32_t)obj->pwm + PWM_mr_offset[obj->channel]);
00081     
00082     // ensure the power is on
00083     if (obj->pwm == LPC_PWM0) {
00084         LPC_SC->PCONP |= 1 << 5;
00085     } else {
00086         LPC_SC->PCONP |= 1 << 6;
00087     }
00088     
00089     obj->pwm->PR = 0;                     // no pre-scale
00090     
00091     // ensure single PWM mode
00092     obj->pwm->MCR = 1 << 1; // reset TC on match 0
00093     
00094     // enable the specific PWM output
00095     obj->pwm->PCR |= 1 << (8 + obj->channel);
00096     
00097     pwm_clock_mhz = PeripheralClock  / 1000000;
00098     
00099     // default to 20ms: standard for servos, and fine for e.g. brightness control
00100     pwmout_period_ms(obj, 20);
00101     pwmout_write    (obj, 0);
00102     
00103     // Wire pinout
00104     pinmap_pinout(pin, PinMap_PWM);
00105 }
00106 
00107 void pwmout_free(pwmout_t* obj) {
00108     // [TODO]
00109 }
00110 
00111 void pwmout_write(pwmout_t* obj, float value) {
00112     if (value < 0.0f) {
00113         value = 0.0;
00114     } else if (value > 1.0f) {
00115         value = 1.0;
00116     }
00117     
00118     // set channel match to percentage
00119     uint32_t v = (uint32_t)((float)(obj->pwm->MR0) * value);
00120     
00121     // workaround for PWM1[1] - Never make it equal MR0, else we get 1 cycle dropout
00122     if (v == obj->pwm->MR0) {
00123         v++;
00124     }
00125     
00126     *obj->MR = v;
00127     
00128     // accept on next period start
00129     obj->pwm->LER |= 1 << obj->channel;
00130 }
00131 
00132 float pwmout_read(pwmout_t* obj) {
00133     float v = (float)(*obj->MR) / (float)(obj->pwm->MR0);
00134     return (v > 1.0f) ? (1.0f) : (v);
00135 }
00136 
00137 void pwmout_period(pwmout_t* obj, float seconds) {
00138     pwmout_period_us(obj, seconds * 1000000.0f);
00139 }
00140 
00141 void pwmout_period_ms(pwmout_t* obj, int ms) {
00142     pwmout_period_us(obj, ms * 1000);
00143 }
00144 
00145 // Set the PWM period, keeping the duty cycle the same.
00146 void pwmout_period_us(pwmout_t* obj, int us) {
00147     // calculate number of ticks
00148     uint32_t ticks = pwm_clock_mhz * us;
00149     
00150     // set reset
00151     obj->pwm->TCR = TCR_RESET;
00152     
00153     // set the global match register
00154     obj->pwm->MR0 = ticks;
00155     
00156     // Scale the pulse width to preserve the duty ratio
00157     if (obj->pwm->MR0 > 0) {
00158         *obj->MR = (*obj->MR * ticks) / obj->pwm->MR0;
00159     }
00160     
00161     // set the channel latch to update value at next period start
00162     obj->pwm->LER |= 1 << 0;
00163     
00164     // enable counter and pwm, clear reset
00165     obj->pwm->TCR = TCR_CNT_EN | TCR_PWM_EN;
00166 }
00167 
00168 void pwmout_pulsewidth(pwmout_t* obj, float seconds) {
00169     pwmout_pulsewidth_us(obj, seconds * 1000000.0f);
00170 }
00171 
00172 void pwmout_pulsewidth_ms(pwmout_t* obj, int ms) {
00173     pwmout_pulsewidth_us(obj, ms * 1000);
00174 }
00175 
00176 void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
00177     // calculate number of ticks
00178     uint32_t v = pwm_clock_mhz * us;
00179     
00180     // workaround for PWM1[1] - Never make it equal MR0, else we get 1 cycle dropout
00181     if (v == obj->pwm->MR0) {
00182         v++;
00183     }
00184     
00185     // set the match register value
00186     *obj->MR = v;
00187     
00188     // set the channel latch to update value at next period start
00189     obj->pwm->LER |= 1 << obj->channel;
00190 }