Diff: targets/TARGET_NXP/TARGET_LPC176X/pwmout_api.c

Revision:

149:156823d33999

Parent:

144:ef7eb2e8f9f7

diff -r 21d94c44109e -r 156823d33999 targets/TARGET_NXP/TARGET_LPC176X/pwmout_api.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/targets/TARGET_NXP/TARGET_LPC176X/pwmout_api.c	Fri Oct 28 11:17:30 2016 +0100
@@ -0,0 +1,171 @@
+/* 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
+
+//  PORT ID, PWM ID, Pin function
+static const PinMap PinMap_PWM[] = {
+    {P1_18, PWM_1, 2},
+    {P1_20, PWM_2, 2},
+    {P1_21, PWM_3, 2},
+    {P1_23, PWM_4, 2},
+    {P1_24, PWM_5, 2},
+    {P1_26, PWM_6, 2},
+    {P2_0 , PWM_1, 1},
+    {P2_1 , PWM_2, 1},
+    {P2_2 , PWM_3, 1},
+    {P2_3 , PWM_4, 1},
+    {P2_4 , PWM_5, 1},
+    {P2_5 , PWM_6, 1},
+    {P3_25, PWM_2, 3},
+    {P3_26, PWM_3, 3},
+    {NC, NC, 0}
+};
+
+__IO uint32_t *PWM_MATCH[] = {
+    &(LPC_PWM1->MR0),
+    &(LPC_PWM1->MR1),
+    &(LPC_PWM1->MR2),
+    &(LPC_PWM1->MR3),
+    &(LPC_PWM1->MR4),
+    &(LPC_PWM1->MR5),
+    &(LPC_PWM1->MR6)
+};
+
+#define TCR_PWM_EN       0x00000008
+
+static unsigned int pwm_clock_mhz;
+
+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;
+    obj->MR = PWM_MATCH[pwm];
+    
+    // ensure the power is on
+    LPC_SC->PCONP |= 1 << 6;
+    
+    // ensure clock to /4
+    LPC_SC->PCLKSEL0 &= ~(0x3 << 12);     // pclk = /4
+    LPC_PWM1->PR = 0;                     // no pre-scale
+    
+    // ensure single PWM mode
+    LPC_PWM1->MCR = 1 << 1; // reset TC on match 0
+    
+    // enable the specific PWM output
+    LPC_PWM1->PCR |= 1 << (8 + pwm);
+    
+    pwm_clock_mhz = SystemCoreClock / 4000000;
+    
+    // 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;
+    }
+    
+    // set channel match to percentage
+    uint32_t v = (uint32_t)((float)(LPC_PWM1->MR0) * value);
+    
+    // workaround for PWM1[1] - Never make it equal MR0, else we get 1 cycle dropout
+    if (v == LPC_PWM1->MR0) {
+        v++;
+    }
+    
+    *obj->MR = v;
+    
+    // accept on next period start
+    LPC_PWM1->LER |= 1 << obj->pwm;
+}
+
+float pwmout_read(pwmout_t* obj) {
+    float v = (float)(*obj->MR) / (float)(LPC_PWM1->MR0);
+    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) {
+    // calculate number of ticks
+    uint32_t ticks = pwm_clock_mhz * us;
+
+    // set reset
+    LPC_PWM1->TCR = TCR_RESET;
+
+    // set the global match register
+    LPC_PWM1->MR0 = ticks;
+
+    // Scale the pulse width to preserve the duty ratio
+    if (LPC_PWM1->MR0 > 0) {
+        *obj->MR = (*obj->MR * ticks) / LPC_PWM1->MR0;
+    }
+
+    // set the channel latch to update value at next period start
+    LPC_PWM1->LER |= 1 << 0;
+
+    // enable counter and pwm, clear reset
+    LPC_PWM1->TCR = TCR_CNT_EN | TCR_PWM_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) {
+    // calculate number of ticks
+    uint32_t v = pwm_clock_mhz * us;
+    
+    // workaround for PWM1[1] - Never make it equal MR0, else we get 1 cycle dropout
+    if (v == LPC_PWM1->MR0) {
+        v++;
+    }
+    
+    // set the match register value
+    *obj->MR = v;
+    
+    // set the channel latch to update value at next period start
+    LPC_PWM1->LER |= 1 << obj->pwm;
+}