Diff: targets/TARGET_NXP/TARGET_LPC15XX/pwmout_api.c

Revision:

149:156823d33999

Parent:

144:ef7eb2e8f9f7

Child:

156:95d6b41a828b

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/targets/TARGET_NXP/TARGET_LPC15XX/pwmout_api.c	Fri Oct 28 11:17:30 2016 +0100
@@ -0,0 +1,202 @@
+/* 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 "mbed_error.h"
+
+static LPC_SCT0_Type *SCTs[4] = {
+    (LPC_SCT0_Type*)LPC_SCT0,
+    (LPC_SCT0_Type*)LPC_SCT1,
+    (LPC_SCT0_Type*)LPC_SCT2,
+    (LPC_SCT0_Type*)LPC_SCT3,
+};
+
+// bit flags for used SCTs
+static unsigned char sct_used = (1 << 3);
+static int get_available_sct(void) {
+    int i;
+    for (i=0; i<4; i++) {
+        if ((sct_used & (1 << i)) == 0)
+            return i;
+    }
+    return -1;
+}
+
+void pwmout_init(pwmout_t* obj, PinName pin) {
+    MBED_ASSERT(pin != (uint32_t)NC);
+
+    int sct_n = get_available_sct();
+    if (sct_n == -1) {
+        error("No available SCT");
+    }
+    
+    sct_used |= (1 << sct_n);
+    obj->pwm =  SCTs[sct_n];
+    obj->pwm_ch = sct_n;
+
+    LPC_SCT0_Type* pwm = obj->pwm;
+
+    // Enable the SCT clock
+    LPC_SYSCON->SYSAHBCLKCTRL1 |= (1 << (obj->pwm_ch + 2));
+
+    // Clear peripheral reset the SCT:
+    LPC_SYSCON->PRESETCTRL1 |=  (1 << (obj->pwm_ch + 2));
+    LPC_SYSCON->PRESETCTRL1 &= ~(1 << (obj->pwm_ch + 2));
+    
+    switch(obj->pwm_ch) {
+        case 0:
+            // SCT0_OUT0
+            LPC_SWM->PINASSIGN[7] &= ~0x0000FF00;
+            LPC_SWM->PINASSIGN[7] |= (pin << 8);
+            break;
+        case 1:
+            // SCT1_OUT0
+            LPC_SWM->PINASSIGN[8] &= ~0x000000FF;
+            LPC_SWM->PINASSIGN[8] |= (pin);
+            break;
+        case 2:
+            // SCT2_OUT0
+            LPC_SWM->PINASSIGN[8] &= ~0xFF000000;
+            LPC_SWM->PINASSIGN[8] |= (pin << 24);
+            break;
+        case 3:
+            // SCT3_OUT0
+            LPC_SWM->PINASSIGN[9] &= ~0x00FF0000;
+            LPC_SWM->PINASSIGN[9] |= (pin << 16);
+            break;
+        default:
+            break;
+    }
+    
+    // Unified 32-bit counter, autolimit
+    pwm->CONFIG |= ((0x3 << 17) | 0x01);
+    
+    // halt and clear the counter
+    pwm->CTRL |= (1 << 2) | (1 << 3);
+    
+    pwm->OUT0_SET = (1 << 0); // event 0
+    pwm->OUT0_CLR = (1 << 1); // event 1
+
+    pwm->EV0_CTRL  = (1 << 12);
+    pwm->EV0_STATE = 0xFFFFFFFF;
+    pwm->EV1_CTRL  = (1 << 12) | (1 << 0);
+    pwm->EV1_STATE = 0xFFFFFFFF;
+
+    // default to 20ms: standard for servos, and fine for e.g. brightness control
+    pwmout_period_ms(obj, 20);
+    pwmout_write    (obj, 0);
+}
+
+void pwmout_free(pwmout_t* obj) {
+    // Disable the SCT clock
+    LPC_SYSCON->SYSAHBCLKCTRL1 &= ~(1 << (obj->pwm_ch + 2));
+    sct_used &= ~(1 << obj->pwm_ch);
+}
+
+void pwmout_write(pwmout_t* obj, float value) {
+    LPC_SCT0_Type* pwm = obj->pwm;
+    if (value < 0.0f) {
+        value = 0.0;
+    } else if (value > 1.0f) {
+        value = 1.0;
+    }
+    uint32_t t_on = (uint32_t)((float)(pwm->MATCHREL0 + 1) * value);
+    if (t_on > 0) {
+        pwm->MATCHREL1 = t_on - 1;
+        
+        // Un-halt the timer and ensure the new pulse-width takes immediate effect if necessary
+        if (pwm->CTRL & (1 << 2)) {
+            pwm->MATCH1 = pwm->MATCHREL1;
+            pwm->CTRL &= ~(1 << 2);
+        }
+    } else {
+        // Halt the timer and force the output low
+        pwm->CTRL |= (1 << 2) | (1 << 3);
+        pwm->OUTPUT = 0x00000000;
+    }
+}
+
+float pwmout_read(pwmout_t* obj) {
+    LPC_SCT0_Type* pwm = obj->pwm;
+    uint32_t t_off = pwm->MATCHREL0 + 1;
+    uint32_t t_on  = (!(pwm->CTRL & (1 << 2))) ? pwm->MATCHREL1 + 1 : 0;
+    float v = (float)t_on/(float)t_off;
+    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) {
+    LPC_SCT0_Type* pwm = obj->pwm;
+    uint32_t t_off = pwm->MATCHREL0 + 1;
+    uint32_t t_on  = (!(pwm->CTRL & (1 << 2))) ? pwm->MATCHREL1 + 1 : 0;
+    float v = (float)t_on/(float)t_off;
+    uint32_t period_ticks = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000);
+    uint32_t pulsewidth_ticks = period_ticks * v;
+    pwm->MATCHREL0 = period_ticks - 1;
+    if (pulsewidth_ticks > 0) {
+        pwm->MATCHREL1 = pulsewidth_ticks - 1;
+        
+        // Un-halt the timer and ensure the new period & pulse-width take immediate effect if necessary
+        if (pwm->CTRL & (1 << 2)) {
+            pwm->MATCH0 = pwm->MATCHREL0;
+            pwm->MATCH1 = pwm->MATCHREL1;
+            pwm->CTRL &= ~(1 << 2);
+        }
+    } else {
+        // Halt the timer and force the output low
+        pwm->CTRL |= (1 << 2) | (1 << 3);
+        pwm->OUTPUT = 0x00000000;
+        
+        // Ensure the new period will take immediate effect when the timer is un-halted
+        pwm->MATCH0 = pwm->MATCHREL0;
+    }
+}
+
+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) {
+    LPC_SCT0_Type* pwm = obj->pwm;
+    if (us > 0) {
+        pwm->MATCHREL1 = (uint32_t)(((uint64_t)SystemCoreClock * (uint64_t)us) / (uint64_t)1000000) - 1;
+        
+        // Un-halt the timer and ensure the new pulse-width takes immediate effect if necessary
+        if (pwm->CTRL & (1 << 2)) {
+            pwm->MATCH1 = pwm->MATCHREL1;
+            pwm->CTRL &= ~(1 << 2);
+        }
+    } else {
+        // Halt the timer and force the output low
+        pwm->CTRL |= (1 << 2) | (1 << 3);
+        pwm->OUTPUT = 0x00000000;
+    }
+}
+