Diff: targets/hal/TARGET_Freescale/TARGET_KL25Z/us_ticker.c

Revision:

13:0645d8841f51

Parent:

10:3bc89ef62ce7

Child:

72:248c61396e08

diff -r 5fa2273de5db -r 0645d8841f51 targets/hal/TARGET_Freescale/TARGET_KL25Z/us_ticker.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/targets/hal/TARGET_Freescale/TARGET_KL25Z/us_ticker.c	Mon Aug 05 14:12:34 2013 +0300
@@ -0,0 +1,146 @@
+/* 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"
+
+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 = 23;
+    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) {
+    /* Clock the timer */
+    SIM->SCGC5 |= SIM_SCGC5_LPTMR_MASK;
+    
+    /* Reset */
+    LPTMR0->CSR = 0;
+    
+    /* Set interrupt handler */
+    NVIC_SetVector(LPTimer_IRQn, (uint32_t)lptmr_isr);
+    NVIC_EnableIRQ(LPTimer_IRQn);
+    
+    /* Clock at (1)MHz -> (1)tick/us */
+    LPTMR0->PSR = LPTMR_PSR_PCS(3);       // OSCERCLK -> 8MHz
+    LPTMR0->PSR |= LPTMR_PSR_PRESCALE(2); // divide by 8
+}
+
+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(unsigned int timestamp) {
+    int delta = (int)(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;
+    }
+}