Diff: targets/TARGET_NXP/TARGET_LPC13XX/pwmout_api.c

Revision:

0:f269e3021894

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/targets/TARGET_NXP/TARGET_LPC13XX/pwmout_api.c	Sun Oct 23 15:10:02 2016 +0000
@@ -0,0 +1,193 @@
+/* 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
+
+/* 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, 2}, {P1_13, PWM_1, 2},    /* MR0 */
+    {P0_9 , PWM_2, 2}, {P1_14, PWM_2, 2},   /* MR1 */
+    {P0_10, PWM_3, 3}, {P1_15, PWM_3, 2},   /* MR2 */
+
+    /* CT16B1 */
+    {P0_21, PWM_4, 1},                      /* MR0 */
+    {P0_22, PWM_5, 2}, {P1_23, PWM_5, 1},   /* MR1 */
+
+    /* CT32B0 */
+    {P0_18, PWM_6, 2}, {P1_24, PWM_6, 1},   /* MR0 */
+    {P0_19, PWM_7, 2}, {P1_25, PWM_7, 1},   /* MR1 */
+    {P0_1 , PWM_8, 2}, {P1_26, PWM_8, 1},   /* MR2 */
+
+    /* CT32B1 */
+    {P0_13, PWM_9 , 3}, //{P1_0, PWM_9 , 1},  /* MR0 */
+    {P0_14, PWM_10, 3}, //{P1_1, PWM_10, 1},  /* MR1 */
+    {P0_15, PWM_11, 3}, //{P1_2, PWM_11, 1},  /* MR2 */
+
+    {NC, NC, 0}
+};
+
+typedef struct {
+    uint8_t timer;
+    uint8_t mr;
+} timer_mr;
+
+static timer_mr pwm_timer_map[11] = {
+    {0, 0}, {0, 1}, {0, 2},
+    {1, 0}, {1, 1},
+    {2, 0}, {2, 1}, {2, 2},
+    {3, 0}, {3, 1}, {3, 2},
+};
+
+static LPC_CTxxBx_Type *Timers[4] = {
+    LPC_CT16B0, LPC_CT16B1,
+    LPC_CT32B0, LPC_CT32B1
+};
+
+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;
+    
+    // Timer registers
+    timer_mr tid = pwm_timer_map[pwm];
+    LPC_CTxxBx_Type *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_CT16B0 || timer == LPC_CT16B1) {
+    /* 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_CTxxBx_Type *timer = Timers[tid.timer];
+    uint32_t t_off = timer->MR3 - (uint32_t)((float)(timer->MR3) * value);
+    
+    // to avoid spike pulse when duty is 0%
+    if (value == 0) {
+        t_off++;
+    }
+    
+    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_CTxxBx_Type *timer = Timers[tid.timer];
+    
+    float v = (float)(timer->MR3 - timer->MR[tid.mr]) / (float)(timer->MR3);
+    if (timer->MR[tid.mr] > timer->MR3) {
+        v = 0.0f;
+    }
+    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;
+    
+    timer_mr tid = pwm_timer_map[obj->pwm];
+    LPC_CTxxBx_Type *timer = Timers[tid.timer];
+    uint32_t old_period_ticks = timer->MR3;
+    uint32_t 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_CTxxBx_Type *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;
+}