John Karatka
mbed
Fork of
mbed-dev
by 
mbed official
Diff: targets/TARGET_NORDIC/TARGET_NRF5/us_ticker.c
- Revision:
- 149:156823d33999
- Child:
- 150:02e0a0aed4ec
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/targets/TARGET_NORDIC/TARGET_NRF5/us_ticker.c Fri Oct 28 11:17:30 2016 +0100
@@ -0,0 +1,562 @@
+/*
+ * Copyright (c) 2013 Nordic Semiconductor ASA
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this list
+ * of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form, except as embedded into a Nordic Semiconductor ASA
+ * integrated circuit in a product or a software update for such product, must reproduce
+ * the above copyright notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of Nordic Semiconductor ASA nor the names of its contributors may be
+ * used to endorse or promote products derived from this software without specific prior
+ * written permission.
+ *
+ * 4. This software, with or without modification, must only be used with a
+ * Nordic Semiconductor ASA integrated circuit.
+ *
+ * 5. Any software provided in binary or object form under this license must not be reverse
+ * engineered, decompiled, modified and/or disassembled.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "us_ticker_api.h"
+#include "common_rtc.h"
+#include "app_util.h"
+#include "nrf_drv_common.h"
+#include "lp_ticker_api.h"
+
+
+//------------------------------------------------------------------------------
+// Common stuff used also by lp_ticker and rtc_api (see "common_rtc.h").
+//
+#include "app_util_platform.h"
+
+bool m_common_rtc_enabled = false;
+uint32_t volatile m_common_rtc_overflows = 0;
+
+#if defined(TARGET_MCU_NRF51822)
+void common_rtc_irq_handler(void)
+#else
+void COMMON_RTC_IRQ_HANDLER(void)
+#endif
+{
+ if (nrf_rtc_event_pending(COMMON_RTC_INSTANCE, US_TICKER_EVENT)) {
+ us_ticker_irq_handler();
+ }
+
+#if DEVICE_LOWPOWERTIMER
+ if (nrf_rtc_event_pending(COMMON_RTC_INSTANCE, LP_TICKER_EVENT)) {
+
+ lp_ticker_irq_handler();
+ }
+#endif
+
+ if (nrf_rtc_event_pending(COMMON_RTC_INSTANCE, NRF_RTC_EVENT_OVERFLOW)) {
+ nrf_rtc_event_clear(COMMON_RTC_INSTANCE, NRF_RTC_EVENT_OVERFLOW);
+ // Don't disable this event. It shall occur periodically.
+
+ ++m_common_rtc_overflows;
+ }
+}
+
+void common_rtc_init(void)
+{
+ if (m_common_rtc_enabled) {
+ return;
+ }
+
+ // RTC is driven by the low frequency (32.768 kHz) clock, a proper request
+ // must be made to have it running.
+ // Currently this clock is started in 'SystemInit' (see "system_nrf51.c"
+ // or "system_nrf52.c", respectively).
+
+ nrf_rtc_prescaler_set(COMMON_RTC_INSTANCE, 0);
+
+ nrf_rtc_event_clear(COMMON_RTC_INSTANCE, US_TICKER_EVENT);
+#if defined(TARGET_MCU_NRF51822)
+ nrf_rtc_event_clear(COMMON_RTC_INSTANCE, OS_TICK_EVENT);
+#endif
+#if DEVICE_LOWPOWERTIMER
+ nrf_rtc_event_clear(COMMON_RTC_INSTANCE, LP_TICKER_EVENT);
+#endif
+ nrf_rtc_event_clear(COMMON_RTC_INSTANCE, NRF_RTC_EVENT_OVERFLOW);
+
+ // Interrupts on all related events are enabled permanently. Particular
+ // events will be enabled or disabled as needed (such approach is more
+ // energy efficient).
+ nrf_rtc_int_enable(COMMON_RTC_INSTANCE,
+ #if defined(TARGET_MCU_NRF51822)
+ OS_TICK_INT_MASK |
+ #endif
+ #if DEVICE_LOWPOWERTIMER
+ LP_TICKER_INT_MASK |
+ #endif
+ US_TICKER_INT_MASK |
+ NRF_RTC_INT_OVERFLOW_MASK);
+
+ // This event is enabled permanently, since overflow indications are needed
+ // continuously.
+ nrf_rtc_event_enable(COMMON_RTC_INSTANCE, NRF_RTC_INT_OVERFLOW_MASK);
+ // All other relevant events are initially disabled.
+ nrf_rtc_event_disable(COMMON_RTC_INSTANCE,
+ #if defined(TARGET_MCU_NRF51822)
+ OS_TICK_INT_MASK |
+ #endif
+ #if DEVICE_LOWPOWERTIMER
+ LP_TICKER_INT_MASK |
+ #endif
+ US_TICKER_INT_MASK);
+
+ nrf_drv_common_irq_enable(nrf_drv_get_IRQn(COMMON_RTC_INSTANCE),
+ APP_IRQ_PRIORITY_LOW);
+
+ nrf_rtc_task_trigger(COMMON_RTC_INSTANCE, NRF_RTC_TASK_START);
+
+ m_common_rtc_enabled = true;
+}
+
+uint32_t common_rtc_32bit_ticks_get(void)
+{
+ uint32_t ticks = nrf_rtc_counter_get(COMMON_RTC_INSTANCE);
+ // The counter used for time measurements is less than 32 bit wide,
+ // so its value is complemented with the number of registered overflows
+ // of the counter.
+ ticks += (m_common_rtc_overflows << RTC_COUNTER_BITS);
+ return ticks;
+}
+
+uint64_t common_rtc_64bit_us_get(void)
+{
+ uint32_t ticks = common_rtc_32bit_ticks_get();
+ // [ticks -> microseconds]
+ return ROUNDED_DIV(((uint64_t)ticks) * 1000000, RTC_INPUT_FREQ);
+}
+
+void common_rtc_set_interrupt(uint32_t us_timestamp, uint32_t cc_channel,
+ uint32_t int_mask)
+{
+ // The internal counter is clocked with a frequency that cannot be easily
+ // multiplied to 1 MHz, therefore besides the translation of values
+ // (microsecond <-> ticks) a special care of overflows handling must be
+ // taken. Here the 32-bit timestamp value is complemented with information
+ // about current the system up time of (ticks + number of overflows of tick
+ // counter on upper bits, converted to microseconds), and such 64-bit value
+ // is then translated to counter ticks. Finally, the lower 24 bits of thus
+ // calculated value is written to the counter compare register to prepare
+ // the interrupt generation.
+ uint64_t current_time64 = common_rtc_64bit_us_get();
+ // [add upper 32 bits from the current time to the timestamp value]
+ uint64_t timestamp64 = us_timestamp +
+ (current_time64 & ~(uint64_t)0xFFFFFFFF);
+ // [if the original timestamp value happens to be after the 32 bit counter
+ // of microsends overflows, correct the upper 32 bits accordingly]
+ if (us_timestamp < (uint32_t)(current_time64 & 0xFFFFFFFF)) {
+ timestamp64 += ((uint64_t)1 << 32);
+ }
+ // [microseconds -> ticks, always round the result up to avoid too early
+ // interrupt generation]
+ uint32_t compare_value =
+ (uint32_t)CEIL_DIV((timestamp64) * RTC_INPUT_FREQ, 1000000);
+
+ // The COMPARE event occurs when the value in compare register is N and
+ // the counter value changes from N-1 to N. Therefore, the minimal safe
+ // difference between the compare value to be set and the current counter
+ // value is 2 ticks. This guarantees that the compare trigger is properly
+ // setup before the compare condition occurs.
+ uint32_t closest_safe_compare = common_rtc_32bit_ticks_get() + 2;
+ if ((int)(compare_value - closest_safe_compare) <= 0) {
+ compare_value = closest_safe_compare;
+ }
+
+ nrf_rtc_cc_set(COMMON_RTC_INSTANCE, cc_channel, RTC_WRAP(compare_value));
+ nrf_rtc_event_enable(COMMON_RTC_INSTANCE, int_mask);
+}
+//------------------------------------------------------------------------------
+
+
+void us_ticker_init(void)
+{
+ common_rtc_init();
+}
+
+uint32_t us_ticker_read()
+{
+ us_ticker_init();
+ return (uint32_t)common_rtc_64bit_us_get();
+}
+
+void us_ticker_set_interrupt(timestamp_t timestamp)
+{
+ common_rtc_set_interrupt(timestamp,
+ US_TICKER_CC_CHANNEL, US_TICKER_INT_MASK);
+}
+
+void us_ticker_disable_interrupt(void)
+{
+ nrf_rtc_event_disable(COMMON_RTC_INSTANCE, US_TICKER_INT_MASK);
+}
+
+void us_ticker_clear_interrupt(void)
+{
+ nrf_rtc_event_clear(COMMON_RTC_INSTANCE, US_TICKER_EVENT);
+}
+
+
+// Since there is no SysTick on NRF51, the RTC1 channel 1 is used as an
+// alternative source of RTOS ticks.
+#if defined(TARGET_MCU_NRF51822)
+
+#include "toolchain.h"
+
+
+#define MAX_RTC_COUNTER_VAL ((1uL << RTC_COUNTER_BITS) - 1)
+
+/**
+ * The value previously set in the capture compare register of channel 1
+ */
+static uint32_t previous_tick_cc_value = 0;
+
+/*
+ RTX provide the following definitions which are used by the tick code:
+ * os_trv: The number (minus 1) of clock cycle between two tick.
+ * os_clockrate: Time duration between two ticks (in us).
+ * OS_Tick_Handler: The function which handle a tick event.
+ This function is special because it never returns.
+ Those definitions are used by the code which handle the os tick.
+ To allow compilation of us_ticker programs without RTOS, those symbols are
+ exported from this module as weak ones.
+ */
+MBED_WEAK uint32_t const os_trv;
+MBED_WEAK uint32_t const os_clockrate;
+MBED_WEAK void OS_Tick_Handler() { }
+
+
+#if defined (__CC_ARM) /* ARMCC Compiler */
+
+__asm void COMMON_RTC_IRQ_HANDLER(void)
+{
+ IMPORT OS_Tick_Handler
+ IMPORT common_rtc_irq_handler
+
+ /**
+ * Chanel 1 of RTC1 is used by RTX as a systick.
+ * If the compare event on channel 1 is set, then branch to OS_Tick_Handler.
+ * Otherwise, just execute common_rtc_irq_handler.
+ * This function has to be written in assembly and tagged as naked because OS_Tick_Handler
+ * will never return.
+ * A c function would put lr on the stack before calling OS_Tick_Handler and this value
+ * would never been dequeued.
+ *
+ * \code
+ * void COMMON_RTC_IRQ_HANDLER(void) {
+ if(NRF_RTC1->EVENTS_COMPARE[1]) {
+ // never return...
+ OS_Tick_Handler();
+ } else {
+ common_rtc_irq_handler();
+ }
+ }
+ * \endcode
+ */
+ ldr r0,=0x40011144
+ ldr r1, [r0, #0]
+ cmp r1, #0
+ beq US_TICKER_HANDLER
+ bl OS_Tick_Handler
+US_TICKER_HANDLER
+ push {r3, lr}
+ bl common_rtc_irq_handler
+ pop {r3, pc}
+ ; ALIGN ;
+}
+
+#elif defined (__GNUC__) /* GNU Compiler */
+
+__attribute__((naked)) void COMMON_RTC_IRQ_HANDLER(void)
+{
+ /**
+ * Chanel 1 of RTC1 is used by RTX as a systick.
+ * If the compare event on channel 1 is set, then branch to OS_Tick_Handler.
+ * Otherwise, just execute common_rtc_irq_handler.
+ * This function has to be written in assembly and tagged as naked because OS_Tick_Handler
+ * will never return.
+ * A c function would put lr on the stack before calling OS_Tick_Handler and this value
+ * would never been dequeued.
+ *
+ * \code
+ * void COMMON_RTC_IRQ_HANDLER(void) {
+ if(NRF_RTC1->EVENTS_COMPARE[1]) {
+ // never return...
+ OS_Tick_Handler();
+ } else {
+ common_rtc_irq_handler();
+ }
+ }
+ * \endcode
+ */
+ __asm__ (
+ "ldr r0,=0x40011144\n"
+ "ldr r1, [r0, #0]\n"
+ "cmp r1, #0\n"
+ "beq US_TICKER_HANDLER\n"
+ "bl OS_Tick_Handler\n"
+ "US_TICKER_HANDLER:\n"
+ "push {r3, lr}\n"
+ "bl common_rtc_irq_handler\n"
+ "pop {r3, pc}\n"
+ "nop"
+ );
+}
+
+#elif defined (__ICCARM__)//IAR
+void common_rtc_irq_handler(void);
+
+__stackless __task void COMMON_RTC_IRQ_HANDLER(void)
+{
+ uint32_t temp;
+
+ __asm volatile(
+ " ldr %[temp], [%[reg2check]] \n"
+ " cmp %[temp], #0 \n"
+ " beq 1f \n"
+ " bl.w OS_Tick_Handler \n"
+ "1: \n"
+ " push {r3, lr}\n"
+ " blx %[rtc_irq] \n"
+ " pop {r3, pc}\n"
+
+ : /* Outputs */
+ [temp] "=&r"(temp)
+ : /* Inputs */
+ [reg2check] "r"(0x40011144),
+ [rtc_irq] "r"(common_rtc_irq_handler)
+ : /* Clobbers */
+ "cc"
+ );
+ (void)temp;
+}
+
+
+#else
+
+#error Compiler not supported.
+#error Provide a definition of COMMON_RTC_IRQ_HANDLER.
+
+/*
+ * Chanel 1 of RTC1 is used by RTX as a systick.
+ * If the compare event on channel 1 is set, then branch to OS_Tick_Handler.
+ * Otherwise, just execute common_rtc_irq_handler.
+ * This function has to be written in assembly and tagged as naked because OS_Tick_Handler
+ * will never return.
+ * A c function would put lr on the stack before calling OS_Tick_Handler and this value
+ * will never been dequeued. After a certain time a stack overflow will happen.
+ *
+ * \code
+ * void COMMON_RTC_IRQ_HANDLER(void) {
+ if(NRF_RTC1->EVENTS_COMPARE[1]) {
+ // never return...
+ OS_Tick_Handler();
+ } else {
+ common_rtc_irq_handler();
+ }
+ }
+ * \endcode
+ */
+
+#endif
+
+/**
+ * Return the next number of clock cycle needed for the next tick.
+ * @note This function has been carrefuly optimized for a systick occuring every 1000us.
+ */
+static uint32_t get_next_tick_cc_delta() {
+ uint32_t delta = 0;
+
+ if (os_clockrate != 1000) {
+ // In RTX, by default SYSTICK is is used.
+ // A tick event is generated every os_trv + 1 clock cycles of the system timer.
+ delta = os_trv + 1;
+ } else {
+ // If the clockrate is set to 1000us then 1000 tick should happen every second.
+ // Unfortunatelly, when clockrate is set to 1000, os_trv is equal to 31.
+ // If (os_trv + 1) is used as the delta value between two ticks, 1000 ticks will be
+ // generated in 32000 clock cycle instead of 32768 clock cycles.
+ // As a result, if a user schedule an OS timer to start in 100s, the timer will start
+ // instead after 97.656s
+ // The code below fix this issue, a clock rate of 1000s will generate 1000 ticks in 32768
+ // clock cycles.
+ // The strategy is simple, for 1000 ticks:
+ // * 768 ticks will occur 33 clock cycles after the previous tick
+ // * 232 ticks will occur 32 clock cycles after the previous tick
+ // By default every delta is equal to 33.
+ // Every five ticks (20%, 200 delta in one second), the delta is equal to 32
+ // The remaining (32) deltas equal to 32 are distributed using primes numbers.
+ static uint32_t counter = 0;
+ if ((counter % 5) == 0 || (counter % 31) == 0 || (counter % 139) == 0 || (counter == 503)) {
+ delta = 32;
+ } else {
+ delta = 33;
+ }
+ ++counter;
+ if (counter == 1000) {
+ counter = 0;
+ }
+ }
+ return delta;
+}
+
+static inline void clear_tick_interrupt() {
+ nrf_rtc_event_clear(COMMON_RTC_INSTANCE, OS_TICK_EVENT);
+ nrf_rtc_event_disable(COMMON_RTC_INSTANCE, OS_TICK_INT_MASK);
+}
+
+/**
+ * Indicate if a value is included in a range which can be wrapped.
+ * @param begin start of the range
+ * @param end end of the range
+ * @param val value to check
+ * @return true if the value is included in the range and false otherwise.
+ */
+static inline bool is_in_wrapped_range(uint32_t begin, uint32_t end, uint32_t val) {
+ // regular case, begin < end
+ // return true if begin <= val < end
+ if (begin < end) {
+ if (begin <= val && val < end) {
+ return true;
+ } else {
+ return false;
+ }
+ } else {
+ // In this case end < begin because it has wrap around the limits
+ // return false if end < val < begin
+ if (end < val && val < begin) {
+ return false;
+ } else {
+ return true;
+ }
+ }
+
+}
+
+/**
+ * Register the next tick.
+ */
+static void register_next_tick() {
+ previous_tick_cc_value = nrf_rtc_cc_get(COMMON_RTC_INSTANCE, OS_TICK_CC_CHANNEL);
+ uint32_t delta = get_next_tick_cc_delta();
+ uint32_t new_compare_value = (previous_tick_cc_value + delta) & MAX_RTC_COUNTER_VAL;
+
+ // Disable irq directly for few cycles,
+ // Validation of the new CC value against the COUNTER,
+ // Setting the new CC value and enabling CC IRQ should be an atomic operation
+ // Otherwise, there is a possibility to set an invalid CC value because
+ // the RTC1 keeps running.
+ // This code is very short 20-38 cycles in the worst case, it shouldn't
+ // disturb softdevice.
+ __disable_irq();
+ uint32_t current_counter = nrf_rtc_counter_get(COMMON_RTC_INSTANCE);
+
+ // If an overflow occur, set the next tick in COUNTER + delta clock cycles
+ if (is_in_wrapped_range(previous_tick_cc_value, new_compare_value, current_counter + 1) == false) {
+ new_compare_value = current_counter + delta;
+ }
+ nrf_rtc_cc_set(COMMON_RTC_INSTANCE, OS_TICK_CC_CHANNEL, new_compare_value);
+ // Enable generation of the compare event for the value set above (this
+ // event will trigger the interrupt).
+ nrf_rtc_event_enable(COMMON_RTC_INSTANCE, OS_TICK_INT_MASK);
+ __enable_irq();
+}
+
+/**
+ * Initialize alternative hardware timer as RTX kernel timer
+ * This function is directly called by RTX.
+ * @note this function shouldn't be called directly.
+ * @return IRQ number of the alternative hardware timer
+ */
+int os_tick_init (void)
+{
+ common_rtc_init();
+
+ nrf_rtc_cc_set(COMMON_RTC_INSTANCE, OS_TICK_CC_CHANNEL, 0);
+ register_next_tick();
+
+ return nrf_drv_get_IRQn(COMMON_RTC_INSTANCE);
+}
+
+/**
+ * Acknowledge the tick interrupt.
+ * This function is called by the function OS_Tick_Handler of RTX.
+ * @note this function shouldn't be called directly.
+ */
+void os_tick_irqack(void)
+{
+ clear_tick_interrupt();
+ register_next_tick();
+}
+
+/**
+ * Returns the overflow flag of the alternative hardware timer.
+ * @note This function is exposed by RTX kernel.
+ * @return 1 if the timer has overflowed and 0 otherwise.
+ */
+uint32_t os_tick_ovf(void) {
+ uint32_t current_counter = nrf_rtc_counter_get(COMMON_RTC_INSTANCE);
+ uint32_t next_tick_cc_value = nrf_rtc_cc_get(COMMON_RTC_INSTANCE, OS_TICK_CC_CHANNEL);
+
+ return is_in_wrapped_range(previous_tick_cc_value, next_tick_cc_value, current_counter) ? 0 : 1;
+}
+
+/**
+ * Return the value of the alternative hardware timer.
+ * @note The documentation is not very clear about what is expected as a result,
+ * is it an ascending counter, a descending one ?
+ * None of this is specified.
+ * The default systick is a descending counter and this function return values in
+ * descending order, even if the internal counter used is an ascending one.
+ * @return the value of the alternative hardware timer.
+ */
+uint32_t os_tick_val(void) {
+ uint32_t current_counter = nrf_rtc_counter_get(COMMON_RTC_INSTANCE);
+ uint32_t next_tick_cc_value = nrf_rtc_cc_get(COMMON_RTC_INSTANCE, OS_TICK_CC_CHANNEL);
+
+ // do not use os_tick_ovf because its counter value can be different
+ if(is_in_wrapped_range(previous_tick_cc_value, next_tick_cc_value, current_counter)) {
+ if (next_tick_cc_value > previous_tick_cc_value) {
+ return next_tick_cc_value - current_counter;
+ } else if(current_counter <= next_tick_cc_value) {
+ return next_tick_cc_value - current_counter;
+ } else {
+ return next_tick_cc_value + (MAX_RTC_COUNTER_VAL - current_counter);
+ }
+ } else {
+ // use (os_trv + 1) has the base step, can be totally inacurate ...
+ uint32_t clock_cycles_by_tick = os_trv + 1;
+
+ // if current counter has wrap arround, add the limit to it.
+ if (current_counter < next_tick_cc_value) {
+ current_counter = current_counter + MAX_RTC_COUNTER_VAL;
+ }
+
+ return clock_cycles_by_tick - ((current_counter - next_tick_cc_value) % clock_cycles_by_tick);
+ }
+
+}
+
+#endif // defined(TARGET_MCU_NRF51822)