tool/mbed/mbed-sdk/libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC81X/pwmout_api.c

   1 /* mbed Microcontroller Library
   2  * Copyright (c) 2006-2013 ARM Limited
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16 #include "mbed_assert.h"
  17 #include "pwmout_api.h"
  18 #include "cmsis.h"
  19 #include "pinmap.h"
  20 #include "mbed_error.h"
  21
  22 // Ported from LPC824 and adapted.
  23
  24 #if DEVICE_PWMOUT
  25
  26 #define PWM_IRQn     SCT_IRQn
  27
  28 // Bit flags for used SCT Outputs
  29 static unsigned char sct_used = 0;
  30 static int sct_inited = 0;
  31
  32 // Find available output channel
  33 // Max number of PWM outputs is 4 on LPC812
  34 static int get_available_sct() {
  35    int i;
  36
  37 // Find available output channel 0..3
  38 // Also need one Match register per channel
  39     for (i = 0; i < CONFIG_SCT_nOU; i++) {
  40 //    for (i = 0; i < 4; i++) {
  41         if ((sct_used & (1 << i)) == 0)
  42             return i;
  43     }
  44     return -1;
  45 }
  46
  47 // Any Port pin may be used for PWM.
  48 // Max number of PWM outputs is 4
  49 void pwmout_init(pwmout_t* obj, PinName pin) {
  50     MBED_ASSERT(pin != (uint32_t)NC);
  51
  52     int sct_n = get_available_sct();
  53     if (sct_n == -1) {
  54         error("No available SCT Output");
  55     }
  56
  57     sct_used |= (1 << sct_n);
  58
  59     obj->pwm =  (LPC_SCT_TypeDef*)LPC_SCT;
  60     obj->pwm_ch = sct_n;
  61
  62     LPC_SCT_TypeDef* pwm = obj->pwm;
  63
  64     // Init SCT on first use
  65     if (! sct_inited) {
  66       sct_inited = 1;
  67
  68       // Enable the SCT clock
  69       LPC_SYSCON->SYSAHBCLKCTRL |= (1 << 8);
  70
  71       // Clear peripheral reset the SCT:
  72       LPC_SYSCON->PRESETCTRL |=  (1 << 8);
  73
  74       // Two 16-bit counters, autolimit (ie reset on Match_0)
  75       //pwm->CONFIG &= ~(0x1);
  76       //pwm->CONFIG |= (1 << 17);
  77       pwm->CONFIG |= ((0x3 << 17) | 0x01);
  78
  79       // halt and clear the counter
  80       pwm->CTRL_U |= (1 << 2) | (1 << 3);
  81
  82       // System Clock (30 Mhz) -> Prescaler -> us_ticker (1 MHz)
  83       pwm->CTRL_U &= ~(0x7F << 5);
  84       pwm->CTRL_U |= (((SystemCoreClock/1000000 - 1) & 0x7F) << 5);
  85
  86       pwm->EVENT[0].CTRL  = (1 << 12) | 0;                     // Event_0 on Match_0
  87       pwm->EVENT[0].STATE = 0xFFFFFFFF;                        // All states
  88
  89       // unhalt the counter:
  90       //    - clearing bit 2 of the CTRL register
  91       pwm->CTRL_U &= ~(1 << 2);
  92
  93       // Not using IRQs
  94       //NVIC_SetVector(PWM_IRQn, (uint32_t)pwm_irq_handler);
  95       //NVIC_EnableIRQ(PWM_IRQn);
  96     }
  97
  98     // LPC81x has only one SCT and 4 Outputs
  99     // LPC82x has only one SCT and 6 Outputs
 100     // LPC1549 has 4 SCTs and 16 Outputs
 101     switch(sct_n) {
 102         case 0:
 103             // SCTx_OUT0
 104             LPC_SWM->PINASSIGN[6] &= ~0xFF000000;
 105             LPC_SWM->PINASSIGN[6] |= (pin << 24);
 106             break;
 107         case 1:
 108             // SCTx_OUT1
 109             LPC_SWM->PINASSIGN[7] &= ~0x000000FF;
 110             LPC_SWM->PINASSIGN[7] |= (pin);
 111             break;
 112         case 2:
 113             // SCTx_OUT2
 114             LPC_SWM->PINASSIGN[7] &= ~0x0000FF00;
 115             LPC_SWM->PINASSIGN[7] |= (pin << 8);
 116             break;
 117         case 3:
 118             // SCTx_OUT3
 119             LPC_SWM->PINASSIGN[7] &= ~0x00FF0000;
 120             LPC_SWM->PINASSIGN[7] |= (pin << 16);
 121             break;
 122         default:
 123             break;
 124     }
 125
 126     pwm->EVENT[sct_n + 1].CTRL  = (1 << 12) | (sct_n + 1);  // Event_n on Match_n
 127     pwm->EVENT[sct_n + 1].STATE = 0xFFFFFFFF;               // All states
 128
 129     pwm->OUT[sct_n].SET = (1 << 0);                         // All PWM channels are SET on Event_0
 130     pwm->OUT[sct_n].CLR = (1 << (sct_n + 1));               // PWM ch is CLRed on Event_(ch+1)
 131
 132     // default to 20ms: standard for servos, and fine for e.g. brightness control
 133     pwmout_period_ms(obj, 20);   // 20ms period
 134     pwmout_write    (obj, 0.0);  //  0ms pulsewidth, dutycycle 0
 135 }
 136
 137 void pwmout_free(pwmout_t* obj) {
 138     // PWM channel is now free
 139     sct_used &= ~(1 << obj->pwm_ch);
 140
 141     // Disable the SCT clock when all channels free
 142     if (sct_used == 0) {
 143       LPC_SYSCON->SYSAHBCLKCTRL &= ~(1 << 8);
 144       sct_inited = 0;
 145     };
 146 }
 147
 148 // Set new dutycycle (0.0 .. 1.0)
 149 void pwmout_write(pwmout_t* obj, float value) {
 150     //value is new dutycycle
 151     if (value < 0.0f) {
 152         value = 0.0;
 153     } else if (value > 1.0f) {
 154         value = 1.0;
 155     }
 156
 157     // Match_0 is PWM period. Compute new endtime of pulse for current channel
 158     uint32_t t_off = (uint32_t)((float)(obj->pwm->MATCHREL[0].U) * value);
 159     obj->pwm->MATCHREL[(obj->pwm_ch) + 1].U = t_off; // New endtime
 160 }
 161
 162 // Get dutycycle (0.0 .. 1.0)
 163 float pwmout_read(pwmout_t* obj) {
 164     uint32_t t_period = obj->pwm->MATCHREL[0].U;
 165
 166     //Sanity check
 167     if (t_period == 0) {
 168      return 0.0;
 169     };
 170
 171     uint32_t t_off  = obj->pwm->MATCHREL[(obj->pwm_ch) + 1].U;
 172     float v = (float)t_off/(float)t_period;
 173     //Sanity check
 174     return (v > 1.0f) ? (1.0f) : (v);
 175 }
 176
 177 // Set the PWM period, keeping the duty cycle the same (for this channel only!).
 178 void pwmout_period(pwmout_t* obj, float seconds){
 179     pwmout_period_us(obj, seconds * 1000000.0f);
 180 }
 181
 182 // Set the PWM period, keeping the duty cycle the same (for this channel only!).
 183 void pwmout_period_ms(pwmout_t* obj, int ms) {
 184     pwmout_period_us(obj, ms * 1000);
 185 }
 186
 187 // Set the PWM period, keeping the duty cycle the same (for this channel only!).
 188 void pwmout_period_us(pwmout_t* obj, int us) {
 189
 190     uint32_t t_period = obj->pwm->MATCHREL[0].U;  // Current PWM period
 191     obj->pwm->MATCHREL[0].U = (uint32_t)us;       // New PWM period
 192
 193     //Keep the dutycycle for the new PWM period
 194     //Should really do this for all active channels!!
 195     //This problem exists in all mbed libs.
 196
 197     //Sanity check
 198     if (t_period == 0) {
 199       return;
 200 //      obj->pwm->MATCHREL[(obj->pwm_ch) + 1].L = 0; // New endtime for this channel
 201     }
 202     else {
 203       uint32_t t_off  = obj->pwm->MATCHREL[(obj->pwm_ch) + 1].U;
 204       float v = (float)t_off/(float)t_period;
 205       obj->pwm->MATCHREL[(obj->pwm_ch) + 1].U = (uint32_t)((float)us * (float)v); // New endtime for this channel
 206     }
 207 }
 208
 209
 210 //Set pulsewidth
 211 void pwmout_pulsewidth(pwmout_t* obj, float seconds) {
 212     pwmout_pulsewidth_us(obj, seconds * 1000000.0f);
 213 }
 214
 215 //Set pulsewidth
 216 void pwmout_pulsewidth_ms(pwmout_t* obj, int ms){
 217     pwmout_pulsewidth_us(obj, ms * 1000);
 218 }
 219
 220 //Set pulsewidth
 221 void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
 222
 223 //Should add Sanity check to make sure pulsewidth < period!
 224     obj->pwm->MATCHREL[(obj->pwm_ch) + 1].U = (uint32_t)us; // New endtime for this channel
 225 }
 226
 227 #endif