Diff: targets/TARGET_NXP/TARGET_LPC81X/pwmout_api.c

Revision:

149:156823d33999

Parent:

144:ef7eb2e8f9f7

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/targets/TARGET_NXP/TARGET_LPC81X/pwmout_api.c	Fri Oct 28 11:17:30 2016 +0100
@@ -0,0 +1,249 @@
+/* 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"
+
+// Ported from LPC824 and adapted.
+
+#if DEVICE_PWMOUT
+
+#define PWM_IRQn     SCT_IRQn
+
+// Bit flags for used SCT Outputs
+static unsigned char sct_used = 0;
+static int sct_inited = 0;
+
+// Find available output channel
+// Max number of PWM outputs is 4 on LPC812
+static int get_available_sct() {
+   int i;
+       
+// Find available output channel 0..3
+// Also need one Match register per channel
+    for (i = 0; i < CONFIG_SCT_nOU; i++) {
+        if ((sct_used & (1 << i)) == 0)
+            return i;
+    }
+    return -1;
+}
+
+// Any Port pin may be used for PWM.
+// Max number of PWM outputs is 4
+void pwmout_init(pwmout_t* obj, PinName pin) {
+    MBED_ASSERT(pin != (PinName)NC);
+
+    int sct_n = get_available_sct();
+    if (sct_n == -1) {
+        error("No available SCT Output");
+    }
+
+    sct_used |= (1 << sct_n);
+
+    obj->pwm =  (LPC_SCT_TypeDef*)LPC_SCT;
+    obj->pwm_ch = sct_n;
+
+    LPC_SCT_TypeDef* pwm = obj->pwm;
+
+    // Init SCT on first use
+    if (! sct_inited) {
+      sct_inited = 1;
+
+      // Enable the SCT clock
+      LPC_SYSCON->SYSAHBCLKCTRL |= (1 << 8);
+
+      // Clear peripheral reset the SCT:
+      LPC_SYSCON->PRESETCTRL |=  (1 << 8);
+
+      // Two 16-bit counters, autolimit (ie reset on Match_0)
+      pwm->CONFIG |= ((0x3 << 17) | 0x01);
+
+      // halt and clear the counter
+      pwm->CTRL_U |= (1 << 2) | (1 << 3);
+
+      // System Clock (30 Mhz) -> Prescaler -> us_ticker (1 MHz)
+      pwm->CTRL_U &= ~(0x7F << 5);
+      pwm->CTRL_U |= (((SystemCoreClock/1000000 - 1) & 0x7F) << 5);
+
+      pwm->EVENT[0].CTRL  = (1 << 12) | 0;                     // Event_0 on Match_0
+      pwm->EVENT[0].STATE = 0xFFFFFFFF;                        // All states
+    
+      // unhalt the counter:
+      //    - clearing bit 2 of the CTRL register
+      pwm->CTRL_U &= ~(1 << 2);
+      
+    }
+
+    // LPC81x has only one SCT and 4 Outputs
+    // LPC82x has only one SCT and 6 Outputs
+    // LPC1549 has 4 SCTs and 16 Outputs    
+    switch(sct_n) {
+        case 0:
+            // SCTx_OUT0
+            LPC_SWM->PINASSIGN[6] &= ~0xFF000000;
+            LPC_SWM->PINASSIGN[6] |= (pin << 24);
+            break;
+        case 1:
+            // SCTx_OUT1
+            LPC_SWM->PINASSIGN[7] &= ~0x000000FF;
+            LPC_SWM->PINASSIGN[7] |= (pin);
+            break;
+        case 2:
+            // SCTx_OUT2
+            LPC_SWM->PINASSIGN[7] &= ~0x0000FF00;
+            LPC_SWM->PINASSIGN[7] |= (pin << 8);
+            break;
+        case 3:
+            // SCTx_OUT3
+            LPC_SWM->PINASSIGN[7] &= ~0x00FF0000;
+            LPC_SWM->PINASSIGN[7] |= (pin << 16);
+            break;
+        default:
+            break;
+    }
+
+    pwm->EVENT[sct_n + 1].CTRL  = (1 << 12) | (sct_n + 1);  // Event_n on Match_n
+    pwm->EVENT[sct_n + 1].STATE = 0xFFFFFFFF;               // All states
+
+    pwm->OUT[sct_n].SET = (1 << 0);                         // All PWM channels are SET on Event_0
+    pwm->OUT[sct_n].CLR = (1 << (sct_n + 1));               // PWM ch is CLRed on Event_(ch+1)
+   
+    // default to 20ms: standard for servos, and fine for e.g. brightness control
+    pwmout_period_ms(obj, 20);   // 20ms period
+    pwmout_write    (obj, 0.0);  //  0ms pulsewidth, dutycycle 0
+}
+
+void pwmout_free(pwmout_t* obj) {
+    // PWM channel is now free
+    sct_used &= ~(1 << obj->pwm_ch);
+    
+    // Disable the SCT clock when all channels free
+    if (sct_used == 0) {  
+      LPC_SYSCON->SYSAHBCLKCTRL &= ~(1 << 8);
+      sct_inited = 0;
+    };  
+}
+
+// Set new dutycycle (0.0 .. 1.0)
+void pwmout_write(pwmout_t* obj, float value) {
+    //value is new dutycycle
+    if (value < 0.0f) {
+        value = 0.0;
+    } else if (value > 1.0f) {
+        value = 1.0;
+    }
+     
+    // Match_0 is PWM period. Compute new endtime of pulse for current channel
+    uint32_t t_off = (uint32_t)((float)(obj->pwm->MATCHREL[0].U) * value);
+    obj->pwm->MATCHREL[(obj->pwm_ch) + 1].U = t_off; // New endtime
+
+    // Clear OxRES (conflict resolution register) bit first, effect of simultaneous set and clear on output x
+    int offset = (obj->pwm_ch * 2);
+    obj->pwm->RES &= ~(0x3 << offset);
+
+    if (value == 0.0f) { // duty is 0%
+        // Clear output
+        obj->pwm->RES |=  (0x2 << offset);
+        // Set CLR event to be same as SET event, makes output to be 0 (low)
+        obj->pwm->OUT[(obj->pwm_ch)].CLR = (1 << 0);
+    } else {
+        // Set output
+        obj->pwm->RES |=  (0x1 << offset);
+        // Use normal CLR event (current SCT ch + 1)
+        obj->pwm->OUT[(obj->pwm_ch)].CLR = (1 << ((obj->pwm_ch) + 1));
+    }
+}
+
+// Get dutycycle (0.0 .. 1.0)
+float pwmout_read(pwmout_t* obj) {
+    uint32_t t_period = obj->pwm->MATCHREL[0].U;
+
+    //Sanity check
+    if (t_period == 0) {
+     return 0.0;
+    };
+     
+    uint32_t t_off  = obj->pwm->MATCHREL[(obj->pwm_ch) + 1].U;
+    float v = (float)t_off/(float)t_period;
+    //Sanity check    
+    return (v > 1.0f) ? (1.0f) : (v);
+}
+
+// Set the PWM period, keeping the duty cycle the same (for this channel only!).
+void pwmout_period(pwmout_t* obj, float seconds){
+    pwmout_period_us(obj, seconds * 1000000.0f);
+}
+
+// Set the PWM period, keeping the duty cycle the same (for this channel only!).
+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 (for this channel only!).
+void pwmout_period_us(pwmout_t* obj, int us) {
+    
+    uint32_t t_period = obj->pwm->MATCHREL[0].U;  // Current PWM period
+    obj->pwm->MATCHREL[0].U = (uint32_t)us;       // New PWM period
+
+    // Sanity check
+    if (t_period == 0) {
+        return;
+    }
+    else {
+        int cnt = sct_used;
+        int ch = 0;
+        // Update match period for exising PWM channels
+        do {
+            // Get current pulse width
+            uint32_t t_off  = obj->pwm->MATCHREL[ch + 1].U;
+            // Get the duty
+            float v = (float)t_off/(float)t_period;
+            // Update pulse width for this channel
+            obj->pwm->MATCHREL[ch + 1].U = (uint32_t)((float)us * (float)v);
+            // Get next used SCT channel
+            cnt = cnt >> 1;
+            ch++;
+        } while (cnt != 0);
+    }
+}
+
+
+//Set pulsewidth
+void pwmout_pulsewidth(pwmout_t* obj, float seconds) {
+    pwmout_pulsewidth_us(obj, seconds * 1000000.0f);
+}
+
+//Set pulsewidth
+void pwmout_pulsewidth_ms(pwmout_t* obj, int ms){
+    pwmout_pulsewidth_us(obj, ms * 1000);
+}
+
+//Set pulsewidth
+void pwmout_pulsewidth_us(pwmout_t* obj, int us) {
+    if (us == 0) {  // pulse width is 0
+        // Set CLR event to be same as SET event, makes output to be 0 (low)
+        obj->pwm->OUT[(obj->pwm_ch)].CLR = (1 << 0);
+    } else {
+        // Use normal CLR event (current SCT ch + 1)
+        obj->pwm->OUT[(obj->pwm_ch)].CLR = (1 << ((obj->pwm_ch) + 1));
+    }
+//Should add Sanity check to make sure pulsewidth < period!
+    obj->pwm->MATCHREL[(obj->pwm_ch) + 1].U = (uint32_t)us; // New endtime for this channel
+}
+
+#endif