Lee Kai Xuan
mbed-os
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erkin yucel
Diff: targets/TARGET_NXP/TARGET_LPC13XX/pwmout_api.c
- Revision:
- 0:f269e3021894
diff -r 000000000000 -r f269e3021894 targets/TARGET_NXP/TARGET_LPC13XX/pwmout_api.c
--- /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;
+}