Diff: targets/TARGET_Maxim/TARGET_MAX32600/us_ticker.c

Revision:

149:156823d33999

Parent:

144:ef7eb2e8f9f7

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/targets/TARGET_Maxim/TARGET_MAX32600/us_ticker.c	Fri Oct 28 11:17:30 2016 +0100
@@ -0,0 +1,263 @@
+/*******************************************************************************
+ * Copyright (C) 2015 Maxim Integrated Products, Inc., All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL MAXIM INTEGRATED BE LIABLE FOR ANY CLAIM, DAMAGES
+ * OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Except as contained in this notice, the name of Maxim Integrated
+ * Products, Inc. shall not be used except as stated in the Maxim Integrated
+ * Products, Inc. Branding Policy.
+ *
+ * The mere transfer of this software does not imply any licenses
+ * of trade secrets, proprietary technology, copyrights, patents,
+ * trademarks, maskwork rights, or any other form of intellectual
+ * property whatsoever. Maxim Integrated Products, Inc. retains all
+ * ownership rights.
+ *******************************************************************************
+ */
+
+#include "mbed_error.h"
+#include "us_ticker_api.h"
+#include "PeripheralNames.h"
+#include "tmr_regs.h"
+
+#define US_TIMER        MXC_TMR0
+#define US_TIMER_IRQn   TMR0_IRQn
+
+static int us_ticker_inited = 0;
+static uint32_t ticks_per_us;
+static uint32_t tick_win;
+static volatile uint64_t current_cnt;   // Hold the current ticks
+static volatile uint64_t event_cnt;     // Holds the value of the next event
+
+#define ticks_to_us(ticks)  ((ticks) / ticks_per_us);
+#define MAX_TICK_VAL    ((uint64_t)0xFFFFFFFF * ticks_per_us)
+
+//******************************************************************************
+static inline void inc_current_cnt(uint32_t inc) {
+
+    // Overflow the ticker when the us ticker overflows
+    current_cnt += inc;
+    if (current_cnt > MAX_TICK_VAL) {
+        current_cnt -= (MAX_TICK_VAL + 1);
+    }
+}
+
+//******************************************************************************
+static inline int event_passed(uint64_t current, uint64_t event) {
+
+    // Determine if the event has already happened.
+    // If the event is behind the current ticker, within a window,
+    // then the event has already happened.
+    if (((current < tick_win) && ((event < current) || 
+        (event > (MAX_TICK_VAL - (tick_win - current))))) || 
+        ((event < current) && (event > (current - tick_win)))) {
+        return 1;
+    }
+
+    return 0;
+}
+
+//******************************************************************************
+static inline uint64_t event_diff(uint64_t current, uint64_t event) {
+
+    // Check to see if the ticker will overflow before the event
+    if(current <= event) {
+        return (event - current);
+    }
+
+    return ((MAX_TICK_VAL - current) + event);
+}
+
+//******************************************************************************
+static void tmr_handler(void)
+{
+    uint32_t term_cnt32 = US_TIMER->term_cnt32;
+    US_TIMER->term_cnt32 = 0xFFFFFFFF;  // reset to max value to prevent further interrupts
+    US_TIMER->intfl = (MXC_F_TMR_INTFL_TIMER0 | MXC_F_TMR_INTFL_TIMER1);    // clear interrupt
+    NVIC_ClearPendingIRQ(US_TIMER_IRQn);
+
+    inc_current_cnt(term_cnt32);
+
+    if (event_passed(current_cnt + US_TIMER->count32, event_cnt )) {
+        // the timestamp has expired
+        event_cnt = 0xFFFFFFFFFFFFFFFFULL;  // reset to max value
+        us_ticker_irq_handler();
+    } else {
+
+        uint64_t diff = event_diff(current_cnt, event_cnt);
+        if (diff < (uint64_t)0xFFFFFFFF) {
+            // the event occurs before the next overflow
+            US_TIMER->term_cnt32 = diff;
+
+            // Since the timer keeps counting after the terminal value is reached, it is possible that the new
+            // terminal value is in the past.    
+            if (US_TIMER->term_cnt32 < US_TIMER->count32) {
+                // the timestamp has expired
+                US_TIMER->term_cnt32 = 0xFFFFFFFF;  // reset to max value to prevent further interrupts
+                US_TIMER->intfl = (MXC_F_TMR_INTFL_TIMER0 | MXC_F_TMR_INTFL_TIMER1);    // clear interrupt
+                NVIC_ClearPendingIRQ(US_TIMER_IRQn);
+                event_cnt = 0xFFFFFFFFFFFFFFFFULL;  // reset to max value
+                us_ticker_irq_handler();
+            }
+        }
+    }
+}
+
+//******************************************************************************
+void us_ticker_init(void)
+{
+    if (us_ticker_inited)
+        return;
+    us_ticker_inited = 1;
+
+    current_cnt = 0;
+    event_cnt = 0xFFFFFFFFFFFFFFFFULL;  // reset to max value
+
+    if (SystemCoreClock <= 1000000) {
+        error("us_ticker cannot operate at this SystemCoreClock");
+        return;
+    }
+
+    // Configure timer for 32-bit continuous mode with /1 prescaler
+    US_TIMER->ctrl = MXC_E_TMR_MODE_CONTINUOUS << MXC_F_TMR_CTRL_MODE_POS | (0 << MXC_F_TMR_CTRL_PRESCALE_POS);
+    ticks_per_us = SystemCoreClock / 1000000;
+
+    // Set the tick window to 10ms
+    tick_win = SystemCoreClock/100;
+
+    // Set timer overflow to the max
+    US_TIMER->term_cnt32 = 0xFFFFFFFF;
+    US_TIMER->pwm_cap32 = 0xFFFFFFFF;
+    US_TIMER->count32 = 0;
+
+    US_TIMER->intfl = (MXC_F_TMR_INTFL_TIMER0 | MXC_F_TMR_INTFL_TIMER1);    // clear pending interrupts
+
+    NVIC_SetVector(US_TIMER_IRQn, (uint32_t)tmr_handler);
+    NVIC_EnableIRQ(US_TIMER_IRQn);
+
+    US_TIMER->inten |= MXC_F_TMR_INTEN_TIMER0;  // enable interrupts
+    US_TIMER->ctrl |= MXC_F_TMR_CTRL_ENABLE0;   // enable timer
+}
+
+//******************************************************************************
+void us_ticker_deinit(void)
+{
+    US_TIMER->ctrl = 0;     // disable timer
+    US_TIMER->inten = 0;    // disable interrupts
+    US_TIMER->intfl = (MXC_F_TMR_INTFL_TIMER0 | MXC_F_TMR_INTFL_TIMER1);    // clear interrupts
+    us_ticker_inited = 0;
+}
+
+//******************************************************************************
+uint32_t us_ticker_read(void)
+{
+    uint64_t current_cnt1, current_cnt2;
+    uint32_t term_cnt, tmr_cnt;
+    uint32_t intfl1, intfl2;
+
+    if (!us_ticker_inited)
+        us_ticker_init();
+
+    // Ensure coherency between current_cnt and US_TIMER->count32
+    do {
+        current_cnt1 = current_cnt;
+        intfl1 = US_TIMER->intfl;
+        term_cnt = US_TIMER->term_cnt32;
+        tmr_cnt = US_TIMER->count32;
+        intfl2 = US_TIMER->intfl;
+        current_cnt2 = current_cnt;
+    } while ((current_cnt1 != current_cnt2) || (intfl1 != intfl2));
+
+    // Account for an unserviced interrupt
+    if (intfl1) {
+        current_cnt1 += term_cnt;
+    }
+
+    current_cnt1 += tmr_cnt;
+
+    return (current_cnt1 / ticks_per_us);
+}
+
+//******************************************************************************
+void us_ticker_set_interrupt(timestamp_t timestamp)
+{
+    // Note: interrupts are disabled before this function is called.
+
+    US_TIMER->ctrl &= ~MXC_F_TMR_CTRL_ENABLE0;  // disable timer
+
+    if (US_TIMER->intfl) {
+        US_TIMER->intfl = (MXC_F_TMR_INTFL_TIMER0 | MXC_F_TMR_INTFL_TIMER1);    // clear interrupt
+        NVIC_ClearPendingIRQ(US_TIMER_IRQn);
+        inc_current_cnt(US_TIMER->term_cnt32);
+    }
+
+    // add and reset the current count value
+    inc_current_cnt(US_TIMER->count32);
+    US_TIMER->count32 = 0;
+
+    // add the number of cycles that the timer is disabled here for 
+    inc_current_cnt(200);
+
+    event_cnt = (uint64_t)timestamp * ticks_per_us;
+
+    // Check to see if the event has already passed
+    if (!event_passed(current_cnt, event_cnt)) {
+        uint64_t diff = event_diff(current_cnt, event_cnt);
+        if (diff < (uint64_t)0xFFFFFFFF) {
+            // the event occurs before the next overflow
+            US_TIMER->term_cnt32 = diff;
+        } else {
+            // the event occurs after the next overflow 
+            US_TIMER->term_cnt32 = 0xFFFFFFFF;  // set to max
+        }
+    } else {
+        // the requested timestamp occurs in the past
+        // set the timer up to immediately expire
+        US_TIMER->term_cnt32 = 1;
+    }
+    US_TIMER->ctrl |= MXC_F_TMR_CTRL_ENABLE0;   // enable timer
+}
+
+//******************************************************************************
+void us_ticker_disable_interrupt(void)
+{
+    // There are no more events, set timer overflow to the max
+    US_TIMER->term_cnt32 = 0xFFFFFFFF;
+}
+
+//******************************************************************************
+void us_ticker_clear_interrupt(void)
+{
+    // cleared in the local handler
+}
+
+//******************************************************************************
+void us_ticker_set(timestamp_t timestamp)
+{
+    US_TIMER->ctrl &= ~MXC_F_TMR_CTRL_ENABLE0;  // disable timer
+    current_cnt = (uint64_t)timestamp * ticks_per_us;
+    US_TIMER->count32 = 0;
+    US_TIMER->term_cnt32 = 0xFFFFFFFF;
+    US_TIMER->ctrl |= MXC_F_TMR_CTRL_ENABLE0;   // enable timer
+
+    if (((uint64_t)timestamp * ticks_per_us) >= event_cnt) {
+        // The next timestamp has elapsed. Trigger the interrupt to handle it.
+        NVIC_SetPendingIRQ(US_TIMER_IRQn);
+    }
+}