Diff: targets/TARGET_NXP/TARGET_LPC11UXX/pwmout_api.c

Revision:

0:f269e3021894

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/targets/TARGET_NXP/TARGET_LPC11UXX/pwmout_api.c	Sun Oct 23 15:10:02 2016 +0000
@@ -0,0 +1,157 @@
+/* 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"
+#include "PeripheralPins.h" // For the Peripheral to Pin Definitions found in the individual Target's Platform
+
+#define TCR_CNT_EN       0x00000001
+#define TCR_RESET        0x00000002
+
+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;
+    
+    // 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);
+    
+    timer->MR[tid.mr] = t_off;
+}
+
+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);
+    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;
+    uint32_t period_ticks = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000);
+    
+    timer_mr tid = pwm_timer_map[obj->pwm];
+    LPC_CTxxBx_Type *timer = Timers[tid.timer];
+    uint32_t old_period_ticks = timer->MR3;
+
+    // for 16bit timer, set prescaler to avoid overflow
+    if (timer == LPC_CT16B0 || timer == LPC_CT16B1) {
+        uint16_t high_period_ticks = period_ticks >> 16;
+        timer->PR = high_period_ticks;
+        period_ticks /= (high_period_ticks + 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);
+        t_on = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000 / (timer->PR + 1));
+    }
+    uint32_t t_off = timer->MR3 - t_on;
+    timer->MR[tid.mr] = t_off;
+    timer->TCR = TCR_CNT_EN;
+}