Lee Kai Xuan
mbed-os
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mbed-os
by 
erkin yucel
Diff: targets/TARGET_Freescale/TARGET_KLXX/us_ticker.c
- Revision:
- 0:f269e3021894
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/targets/TARGET_Freescale/TARGET_KLXX/us_ticker.c Sun Oct 23 15:10:02 2016 +0000
@@ -0,0 +1,204 @@
+/* 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 <stddef.h>
+#include "us_ticker_api.h"
+#include "PeripheralNames.h"
+#include "clk_freqs.h"
+
+static void pit_init(void);
+static void lptmr_init(void);
+
+static int us_ticker_inited = 0;
+
+void us_ticker_init(void) {
+ if (us_ticker_inited) return;
+ us_ticker_inited = 1;
+
+ pit_init();
+ lptmr_init();
+}
+
+/******************************************************************************
+ * Timer for us timing.
+ ******************************************************************************/
+static void pit_init(void) {
+ SIM->SCGC6 |= SIM_SCGC6_PIT_MASK; // Clock PIT
+ PIT->MCR = 0; // Enable PIT
+
+ // Channel 1
+ PIT->CHANNEL[1].LDVAL = 0xFFFFFFFF;
+ PIT->CHANNEL[1].TCTRL = PIT_TCTRL_CHN_MASK; // Chain to timer 0, disable Interrupts
+ PIT->CHANNEL[1].TCTRL |= PIT_TCTRL_TEN_MASK; // Start timer 1
+
+ // Use channel 0 as a prescaler for channel 1
+ PIT->CHANNEL[0].LDVAL = (bus_frequency() + 500000) / 1000000 - 1;
+ PIT->CHANNEL[0].TCTRL = PIT_TCTRL_TEN_MASK; // Start timer 0, disable interrupts
+}
+
+uint32_t us_ticker_read() {
+ if (!us_ticker_inited)
+ us_ticker_init();
+
+ // The PIT is a countdown timer
+ return ~(PIT->CHANNEL[1].CVAL);
+}
+
+/******************************************************************************
+ * Timer Event
+ *
+ * It schedules interrupts at given (32bit)us interval of time.
+ * It is implemented used the 16bit Low Power Timer that remains powered in all
+ * power modes.
+ ******************************************************************************/
+static void lptmr_isr(void);
+
+static void lptmr_init(void) {
+ uint32_t extosc;
+
+ /* Clock the timer */
+ SIM->SCGC5 |= SIM_SCGC5_LPTMR_MASK;
+
+ /* Reset */
+ LPTMR0->CSR = 0;
+
+#if defined(TARGET_KL43Z)
+ /* Set interrupt handler */
+ NVIC_SetVector(LPTMR0_IRQn, (uint32_t)lptmr_isr);
+ NVIC_EnableIRQ(LPTMR0_IRQn);
+
+
+ MCG->C1 |= MCG_C1_IRCLKEN_MASK;
+ extosc = mcgirc_frequency();
+#else
+ /* Set interrupt handler */
+ NVIC_SetVector(LPTimer_IRQn, (uint32_t)lptmr_isr);
+ NVIC_EnableIRQ(LPTimer_IRQn);
+
+ /* Clock at (1)MHz -> (1)tick/us */
+ /* Check if the external oscillator can be divided to 1MHz */
+ extosc = extosc_frequency();
+#endif
+ if (extosc != 0) { //If external oscillator found
+ if (extosc % 1000000u == 0) { //If it is a multiple if 1MHz
+ extosc /= 1000000;
+ if (extosc == 1) { //1MHz, set timerprescaler in bypass mode
+ LPTMR0->PSR = LPTMR_PSR_PCS(3) | LPTMR_PSR_PBYP_MASK;
+ return;
+ } else { //See if we can divide it to 1MHz
+ uint32_t divider = 0;
+ extosc >>= 1;
+ while (1) {
+ if (extosc == 1) {
+ LPTMR0->PSR = LPTMR_PSR_PCS(3) | LPTMR_PSR_PRESCALE(divider);
+ return;
+ }
+ if (extosc % 2 != 0) //If we can't divide by two anymore
+ break;
+ divider++;
+ extosc >>= 1;
+ }
+ }
+ }
+ }
+#if defined(TARGET_KL43Z)
+ //No suitable actual IRC oscillator clock -> Set it to (8MHz / divider)
+ MCG->SC &= ~MCG_SC_FCRDIV_MASK;
+ MCG->MC &= ~MCG->MC & MCG_MC_LIRC_DIV2_MASK;
+ LPTMR0->PSR = LPTMR_PSR_PCS(0) | LPTMR_PSR_PRESCALE(2);
+#else
+ //No suitable external oscillator clock -> Use fast internal oscillator (4MHz / divider)
+ MCG->C1 |= MCG_C1_IRCLKEN_MASK;
+ MCG->C2 |= MCG_C2_IRCS_MASK;
+ LPTMR0->PSR = LPTMR_PSR_PCS(0);
+ switch (MCG->SC & MCG_SC_FCRDIV_MASK) {
+ case MCG_SC_FCRDIV(0): //4MHz
+ LPTMR0->PSR |= LPTMR_PSR_PRESCALE(1);
+ break;
+ case MCG_SC_FCRDIV(1): //2MHz
+ LPTMR0->PSR |= LPTMR_PSR_PRESCALE(0);
+ break;
+ default: //1MHz or anything else, in which case we put it on 1MHz
+ MCG->SC &= ~MCG_SC_FCRDIV_MASK;
+ MCG->SC |= MCG_SC_FCRDIV(2);
+ LPTMR0->PSR |= LPTMR_PSR_PBYP_MASK;
+ }
+#endif
+}
+
+void us_ticker_disable_interrupt(void) {
+ LPTMR0->CSR &= ~LPTMR_CSR_TIE_MASK;
+}
+
+void us_ticker_clear_interrupt(void) {
+ // we already clear interrupt in lptmr_isr
+}
+
+static uint32_t us_ticker_int_counter = 0;
+static uint16_t us_ticker_int_remainder = 0;
+
+static void lptmr_set(unsigned short count) {
+ /* Reset */
+ LPTMR0->CSR = 0;
+
+ /* Set the compare register */
+ LPTMR0->CMR = count;
+
+ /* Enable interrupt */
+ LPTMR0->CSR |= LPTMR_CSR_TIE_MASK;
+
+ /* Start the timer */
+ LPTMR0->CSR |= LPTMR_CSR_TEN_MASK;
+}
+
+static void lptmr_isr(void) {
+ // write 1 to TCF to clear the LPT timer compare flag
+ LPTMR0->CSR |= LPTMR_CSR_TCF_MASK;
+
+ if (us_ticker_int_counter > 0) {
+ lptmr_set(0xFFFF);
+ us_ticker_int_counter--;
+
+ } else {
+ if (us_ticker_int_remainder > 0) {
+ lptmr_set(us_ticker_int_remainder);
+ us_ticker_int_remainder = 0;
+
+ } else {
+ // This function is going to disable the interrupts if there are
+ // no other events in the queue
+ us_ticker_irq_handler();
+ }
+ }
+}
+
+void us_ticker_set_interrupt(timestamp_t timestamp) {
+ int delta = (int)((uint32_t)timestamp - us_ticker_read());
+ if (delta <= 0) {
+ // This event was in the past:
+ us_ticker_irq_handler();
+ return;
+ }
+
+ us_ticker_int_counter = (uint32_t)(delta >> 16);
+ us_ticker_int_remainder = (uint16_t)(0xFFFF & delta);
+ if (us_ticker_int_counter > 0) {
+ lptmr_set(0xFFFF);
+ us_ticker_int_counter--;
+ } else {
+ lptmr_set(us_ticker_int_remainder);
+ us_ticker_int_remainder = 0;
+ }
+}