Johannes Stratmann / mbed-dev

added prescaler for 16 bit pwm in LPC1347 target

Fork of mbed-dev by mbed official

targets/hal/TARGET_Freescale/TARGET_K20XX/pwmout_api.c@147:ba84b7dc41a7, 2016-09-10 (annotated)

Committer:
JojoS
Date:
Sat Sep 10 15:32:04 2016 +0000
Revision:
147:ba84b7dc41a7
Parent:
144:ef7eb2e8f9f7 
added prescaler for 16 bit timers (solution as in LPC11xx), default prescaler 31 for max 28 ms period time

Who changed what in which revision?

UserRevisionLine numberNew contents of line
<> 144:ef7eb2e8f9f7 1 /* mbed Microcontroller Library
<> 144:ef7eb2e8f9f7 2 * Copyright (c) 2006-2015 ARM Limited
<> 144:ef7eb2e8f9f7 3 *
<> 144:ef7eb2e8f9f7 4 * Licensed under the Apache License, Version 2.0 (the "License");
<> 144:ef7eb2e8f9f7 5 * you may not use this file except in compliance with the License.
<> 144:ef7eb2e8f9f7 6 * You may obtain a copy of the License at
<> 144:ef7eb2e8f9f7 7 *
<> 144:ef7eb2e8f9f7 8 * http://www.apache.org/licenses/LICENSE-2.0
<> 144:ef7eb2e8f9f7 9 *
<> 144:ef7eb2e8f9f7 10 * Unless required by applicable law or agreed to in writing, software
<> 144:ef7eb2e8f9f7 11 * distributed under the License is distributed on an "AS IS" BASIS,
<> 144:ef7eb2e8f9f7 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
<> 144:ef7eb2e8f9f7 13 * See the License for the specific language governing permissions and
<> 144:ef7eb2e8f9f7 14 * limitations under the License.
<> 144:ef7eb2e8f9f7 15 */
<> 144:ef7eb2e8f9f7 16 #include "mbed_assert.h"
<> 144:ef7eb2e8f9f7 17 #include "pwmout_api.h"
<> 144:ef7eb2e8f9f7 18
<> 144:ef7eb2e8f9f7 19 #include "cmsis.h"
<> 144:ef7eb2e8f9f7 20 #include "pinmap.h"
<> 144:ef7eb2e8f9f7 21 #include "PeripheralPins.h"
<> 144:ef7eb2e8f9f7 22
<> 144:ef7eb2e8f9f7 23 static float pwm_clock = 0;
<> 144:ef7eb2e8f9f7 24
<> 144:ef7eb2e8f9f7 25 void pwmout_init(pwmout_t* obj, PinName pin) {
<> 144:ef7eb2e8f9f7 26 // determine the channel
<> 144:ef7eb2e8f9f7 27 PWMName pwm = (PWMName)pinmap_peripheral(pin, PinMap_PWM);
<> 144:ef7eb2e8f9f7 28 MBED_ASSERT(pwm != (PWMName)NC);
<> 144:ef7eb2e8f9f7 29
<> 144:ef7eb2e8f9f7 30 uint32_t clkdiv = 0;
<> 144:ef7eb2e8f9f7 31 float clkval = SystemCoreClock / 1000000.0f;
<> 144:ef7eb2e8f9f7 32
<> 144:ef7eb2e8f9f7 33 while (clkval > 1) {
<> 144:ef7eb2e8f9f7 34 clkdiv++;
<> 144:ef7eb2e8f9f7 35 clkval /= 2.0;
<> 144:ef7eb2e8f9f7 36 if (clkdiv == 7)
<> 144:ef7eb2e8f9f7 37 break;
<> 144:ef7eb2e8f9f7 38 }
<> 144:ef7eb2e8f9f7 39
<> 144:ef7eb2e8f9f7 40 pwm_clock = clkval;
<> 144:ef7eb2e8f9f7 41 unsigned int ftm_n = (pwm >> TPM_SHIFT);
<> 144:ef7eb2e8f9f7 42 unsigned int ch_n = (pwm & 0xFF);
<> 144:ef7eb2e8f9f7 43
<> 144:ef7eb2e8f9f7 44 SIM->SCGC6 |= 1 << (SIM_SCGC6_FTM0_SHIFT + ftm_n);
<> 144:ef7eb2e8f9f7 45
<> 144:ef7eb2e8f9f7 46 FTM_Type *ftm = (FTM_Type *)(FTM0_BASE + 0x1000 * ftm_n);
<> 144:ef7eb2e8f9f7 47 ftm->CONF |= FTM_CONF_BDMMODE(3);
<> 144:ef7eb2e8f9f7 48 ftm->SC = FTM_SC_CLKS(1) | FTM_SC_PS(clkdiv); // (clock)MHz / clkdiv ~= (0.75)MHz
<> 144:ef7eb2e8f9f7 49 ftm->CONTROLS[ch_n].CnSC = (FTM_CnSC_MSB_MASK | FTM_CnSC_ELSB_MASK); /* No Interrupts; High True pulses on Edge Aligned PWM */
<> 144:ef7eb2e8f9f7 50 ftm->MODE = FTM_MODE_FTMEN_MASK;
<> 144:ef7eb2e8f9f7 51 ftm->SYNC = FTM_SYNC_CNTMIN_MASK;
<> 144:ef7eb2e8f9f7 52 ftm->SYNCONF = FTM_SYNCONF_SYNCMODE_MASK | FTM_SYNCONF_SWSOC_MASK | FTM_SYNCONF_SWWRBUF_MASK;
<> 144:ef7eb2e8f9f7 53
<> 144:ef7eb2e8f9f7 54 //Without SYNCEN set CnV does not seem to update
<> 144:ef7eb2e8f9f7 55 ftm->COMBINE = FTM_COMBINE_SYNCEN0_MASK | FTM_COMBINE_SYNCEN1_MASK | FTM_COMBINE_SYNCEN2_MASK | FTM_COMBINE_SYNCEN3_MASK;
<> 144:ef7eb2e8f9f7 56
<> 144:ef7eb2e8f9f7 57 obj->CnV = &ftm->CONTROLS[ch_n].CnV;
<> 144:ef7eb2e8f9f7 58 obj->MOD = &ftm->MOD;
<> 144:ef7eb2e8f9f7 59 obj->SYNC = &ftm->SYNC;
<> 144:ef7eb2e8f9f7 60
<> 144:ef7eb2e8f9f7 61 // default to 20ms: standard for servos, and fine for e.g. brightness control
<> 144:ef7eb2e8f9f7 62 pwmout_period_ms(obj, 20);
<> 144:ef7eb2e8f9f7 63 pwmout_write(obj, 0.0);
<> 144:ef7eb2e8f9f7 64
<> 144:ef7eb2e8f9f7 65 // Wire pinout
<> 144:ef7eb2e8f9f7 66 pinmap_pinout(pin, PinMap_PWM);
<> 144:ef7eb2e8f9f7 67 }
<> 144:ef7eb2e8f9f7 68
<> 144:ef7eb2e8f9f7 69 void pwmout_free(pwmout_t* obj) {}
<> 144:ef7eb2e8f9f7 70
<> 144:ef7eb2e8f9f7 71 void pwmout_write(pwmout_t* obj, float value) {
<> 144:ef7eb2e8f9f7 72 if (value < 0.0) {
<> 144:ef7eb2e8f9f7 73 value = 0.0;
<> 144:ef7eb2e8f9f7 74 } else if (value > 1.0) {
<> 144:ef7eb2e8f9f7 75 value = 1.0;
<> 144:ef7eb2e8f9f7 76 }
<> 144:ef7eb2e8f9f7 77
<> 144:ef7eb2e8f9f7 78 while(*obj->SYNC & FTM_SYNC_SWSYNC_MASK);
<> 144:ef7eb2e8f9f7 79 *obj->CnV = (uint32_t)((float)(*obj->MOD + 1) * value);
<> 144:ef7eb2e8f9f7 80 *obj->SYNC |= FTM_SYNC_SWSYNC_MASK;
<> 144:ef7eb2e8f9f7 81 }
<> 144:ef7eb2e8f9f7 82
<> 144:ef7eb2e8f9f7 83 float pwmout_read(pwmout_t* obj) {
<> 144:ef7eb2e8f9f7 84 while(*obj->SYNC & FTM_SYNC_SWSYNC_MASK);
<> 144:ef7eb2e8f9f7 85 float v = (float)(*obj->CnV) / (float)(*obj->MOD + 1);
<> 144:ef7eb2e8f9f7 86 return (v > 1.0) ? (1.0) : (v);
<> 144:ef7eb2e8f9f7 87 }
<> 144:ef7eb2e8f9f7 88
<> 144:ef7eb2e8f9f7 89 void pwmout_period(pwmout_t* obj, float seconds) {
<> 144:ef7eb2e8f9f7 90 pwmout_period_us(obj, seconds * 1000000.0f);
<> 144:ef7eb2e8f9f7 91 }
<> 144:ef7eb2e8f9f7 92
<> 144:ef7eb2e8f9f7 93 void pwmout_period_ms(pwmout_t* obj, int ms) {
<> 144:ef7eb2e8f9f7 94 pwmout_period_us(obj, ms * 1000);
<> 144:ef7eb2e8f9f7 95 }
<> 144:ef7eb2e8f9f7 96
<> 144:ef7eb2e8f9f7 97 // Set the PWM period, keeping the duty cycle the same.
<> 144:ef7eb2e8f9f7 98 void pwmout_period_us(pwmout_t* obj, int us) {
<> 144:ef7eb2e8f9f7 99 float dc = pwmout_read(obj);
<> 144:ef7eb2e8f9f7 100 *obj->MOD = (uint32_t)(pwm_clock * (float)us) - 1;
<> 144:ef7eb2e8f9f7 101 *obj->SYNC |= FTM_SYNC_SWSYNC_MASK;
<> 144:ef7eb2e8f9f7 102 pwmout_write(obj, dc);
<> 144:ef7eb2e8f9f7 103 }
<> 144:ef7eb2e8f9f7 104
<> 144:ef7eb2e8f9f7 105 void pwmout_pulsewidth(pwmout_t* obj, float seconds) {
<> 144:ef7eb2e8f9f7 106 pwmout_pulsewidth_us(obj, seconds * 1000000.0f);
<> 144:ef7eb2e8f9f7 107 }
<> 144:ef7eb2e8f9f7 108
<> 144:ef7eb2e8f9f7 109 void pwmout_pulsewidth_ms(pwmout_t* obj, int ms) {
<> 144:ef7eb2e8f9f7 110 pwmout_pulsewidth_us(obj, ms * 1000);
<> 144:ef7eb2e8f9f7 111 }
<> 144:ef7eb2e8f9f7 112
<> 144:ef7eb2e8f9f7 113 void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
<> 144:ef7eb2e8f9f7 114 *obj->CnV = (uint32_t)(pwm_clock * (float)us);
<> 144:ef7eb2e8f9f7 115 *obj->SYNC |= FTM_SYNC_SWSYNC_MASK;
<> 144:ef7eb2e8f9f7 116 }