Diff: mbed-dev/targets/TARGET_Maxim/TARGET_MAX32625/us_ticker.c

Revision:

18:6a4db94011d3

diff -r f713758f6238 -r 6a4db94011d3 mbed-dev/targets/TARGET_Maxim/TARGET_MAX32625/us_ticker.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-dev/targets/TARGET_Maxim/TARGET_MAX32625/us_ticker.c	Sun May 14 23:18:57 2017 +0000
@@ -0,0 +1,257 @@
+/*******************************************************************************
+ * Copyright (c) 2016 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 <stddef.h>
+#include "mbed_error.h"
+#include "us_ticker_api.h"
+#include "PeripheralNames.h"
+#include "tmr.h"
+
+#define US_TIMER        MXC_TMR0
+#define US_TIMER_IRQn   TMR0_0_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 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 cmp = TMR32_GetCompare(US_TIMER);
+    TMR32_SetCompare(US_TIMER, 0xFFFFFFFF); // reset to max value to prevent further interrupts
+    TMR32_ClearFlag(US_TIMER);
+    NVIC_ClearPendingIRQ(US_TIMER_IRQn);
+
+    inc_current_cnt(cmp);
+
+    if (event_passed(current_cnt + TMR32_GetCount(US_TIMER), 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
+            TMR32_SetCompare(US_TIMER, 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 (TMR32_GetCompare(US_TIMER) < TMR32_GetCount(US_TIMER)) {
+                // the timestamp has expired
+                TMR32_SetCompare(US_TIMER, 0xFFFFFFFF); // reset to max value to prevent further interrupts
+                TMR32_ClearFlag(US_TIMER);
+                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
+    ticks_per_us = SystemCoreClock / 1000000;
+    tick_win = SystemCoreClock / 100;           // Set the tick window to 10ms
+
+    int retval = TMR_Init(US_TIMER, TMR_PRESCALE_DIV_2_0, NULL);
+    MBED_ASSERT(retval == E_NO_ERROR);
+
+    tmr32_cfg_t cfg;
+    cfg.mode = TMR32_MODE_CONTINUOUS;
+    cfg.polarity = TMR_POLARITY_UNUSED;
+    cfg.compareCount = 0xFFFFFFFF;
+    TMR32_Config(US_TIMER, &cfg);
+
+    NVIC_SetVector(US_TIMER_IRQn, (uint32_t)tmr_handler);
+    NVIC_EnableIRQ(US_TIMER_IRQn);
+    TMR32_EnableINT(US_TIMER);
+
+    TMR32_Start(US_TIMER);
+}
+
+//******************************************************************************
+void us_ticker_deinit(void)
+{
+    TMR32_Stop(US_TIMER);
+    TMR32_DisableINT(US_TIMER);
+    TMR32_ClearFlag(US_TIMER);
+    us_ticker_inited = 0;
+}
+
+//******************************************************************************
+uint32_t us_ticker_read(void)
+{
+    uint64_t current_cnt1, current_cnt2;
+    uint32_t cmp, cnt;
+    uint32_t flag1, flag2;
+
+    if (!us_ticker_inited) {
+        us_ticker_init();
+    }
+
+    // Ensure coherency between current_cnt and TMR32_GetCount()
+    do {
+        current_cnt1 = current_cnt;
+        flag1 = TMR32_GetFlag(US_TIMER);
+        cmp = TMR32_GetCompare(US_TIMER);
+        cnt = TMR32_GetCount(US_TIMER);
+        flag2 = TMR32_GetFlag(US_TIMER);
+        current_cnt2 = current_cnt;
+    } while ((current_cnt1 != current_cnt2) || (flag1 != flag2));
+
+    // Account for an unserviced interrupt
+    if (flag1) {
+        current_cnt1 += cmp;
+    }
+
+    current_cnt1 += cnt;
+
+    return (current_cnt1 / ticks_per_us);
+}
+
+//******************************************************************************
+void us_ticker_set_interrupt(timestamp_t timestamp)
+{
+    // Note: interrupts are disabled before this function is called.
+
+    TMR32_Stop(US_TIMER);
+
+    if (TMR32_GetFlag(US_TIMER)) {
+        TMR32_ClearFlag(US_TIMER);
+        NVIC_ClearPendingIRQ(US_TIMER_IRQn);
+        inc_current_cnt(TMR32_GetCompare(US_TIMER));
+    }
+
+    // add and reset the current count value
+    inc_current_cnt(TMR32_GetCount(US_TIMER));
+    TMR32_SetCount(US_TIMER, 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
+            TMR32_SetCompare(US_TIMER, diff);
+        } else {
+            // the event occurs after the next overflow
+            TMR32_SetCompare(US_TIMER, 0xFFFFFFFF);  // set to max
+        }
+    } else {
+        // the requested timestamp occurs in the past
+        // set the timer up to immediately expire
+        TMR32_SetCompare(US_TIMER, 1);
+    }
+
+    TMR32_Start(US_TIMER);
+}
+
+//******************************************************************************
+void us_ticker_disable_interrupt(void)
+{
+    // There are no more events, set timer overflow to the max
+    TMR32_SetCompare(US_TIMER, 0xFFFFFFFF);
+}
+
+//******************************************************************************
+void us_ticker_clear_interrupt(void)
+{
+    // cleared in the local handler
+}
+
+//******************************************************************************
+void us_ticker_set(timestamp_t timestamp)
+{
+    TMR32_Stop(US_TIMER);
+    current_cnt = (uint64_t)timestamp * ticks_per_us;
+    TMR32_SetCount(US_TIMER, 0);
+    TMR32_SetCompare(US_TIMER, 0xFFFFFFFF);
+    TMR32_Start(US_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);
+    }
+}