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Diff: targets/hal/TARGET_Silicon_Labs/TARGET_EFM32/us_ticker.c
- Revision:
- 0:9b334a45a8ff
- Child:
- 144:ef7eb2e8f9f7
diff -r 000000000000 -r 9b334a45a8ff targets/hal/TARGET_Silicon_Labs/TARGET_EFM32/us_ticker.c --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/targets/hal/TARGET_Silicon_Labs/TARGET_EFM32/us_ticker.c Thu Oct 01 15:25:22 2015 +0300 @@ -0,0 +1,220 @@ +/***************************************************************************//** + * @file us_ticker.c + ******************************************************************************* + * @section License + * <b>(C) Copyright 2015 Silicon Labs, http://www.silabs.com</b> + ******************************************************************************* + * + * Permission is granted to anyone to use this software for any purpose, + * including commercial applications, and to alter it and redistribute it + * freely, subject to the following restrictions: + * + * 1. The origin of this software must not be misrepresented; you must not + * claim that you wrote the original software. + * 2. Altered source versions must be plainly marked as such, and must not be + * misrepresented as being the original software. + * 3. This notice may not be removed or altered from any source distribution. + * + * DISCLAIMER OF WARRANTY/LIMITATION OF REMEDIES: Silicon Labs has no + * obligation to support this Software. Silicon Labs is providing the + * Software "AS IS", with no express or implied warranties of any kind, + * including, but not limited to, any implied warranties of merchantability + * or fitness for any particular purpose or warranties against infringement + * of any proprietary rights of a third party. + * + * Silicon Labs will not be liable for any consequential, incidental, or + * special damages, or any other relief, or for any claim by any third party, + * arising from your use of this Software. + * + ******************************************************************************/ + +#include <stddef.h> +#include "us_ticker_api.h" +#include "cmsis.h" +#include "mbed_assert.h" +#include "em_cmu.h" +#include "em_timer.h" +#include "device_peripherals.h" +#include "device.h" +#include "clocking.h" +#include "sleep_api.h" +#include "sleepmodes.h" + +#define TIMER_LEAST_ACTIVE_SLEEPMODE EM1 +/** + * Timer functions for microsecond ticker. + * mbed expects a 32-bit timer. Since the EFM32 only has 16-bit timers, + * the upper 16 bits are implemented in software. + */ + +static uint8_t us_ticker_inited = 0; // Is ticker initialized yet + +static volatile uint32_t ticker_cnt = 0x2ff00; //Internal overflow count, used to extend internal 16-bit counter to (MHz * 32-bit) +static volatile uint16_t ticker_int_rem = 0; //Timer match value for user interrupt +static volatile uint32_t ticker_int_cnt = 0; //Amount of overflows until user interrupt +static volatile uint8_t ticker_freq_mhz = 0; //Frequency of timer in MHz + +void us_ticker_irq_handler_internal(void) +{ + /* Check for user interrupt expiration */ + if (TIMER_IntGet(US_TICKER_TIMER) & TIMER_IF_CC0) { + if (ticker_int_rem > 0) { + TIMER_CompareSet(US_TICKER_TIMER, 0, ticker_int_rem); + ticker_int_rem = 0; + TIMER_IntClear(US_TICKER_TIMER, TIMER_IF_CC0); + } else if (ticker_int_cnt > 0) { + ticker_int_cnt--; + TIMER_IntClear(US_TICKER_TIMER, TIMER_IF_CC0); + } else { + us_ticker_irq_handler(); + } + } + + /* Handle timer overflow */ + if (TIMER_IntGet(US_TICKER_TIMER) & TIMER_IF_OF) { + ticker_cnt++; + if(ticker_cnt >= (((uint32_t)ticker_freq_mhz) << 16)) ticker_cnt = 0; + TIMER_IntClear(US_TICKER_TIMER, TIMER_IF_OF); + } +} + +void us_ticker_init(void) +{ + if (us_ticker_inited) { + return; + } + us_ticker_inited = 1; + + /* Enable clock for TIMERs */ + CMU_ClockEnable(US_TICKER_TIMER_CLOCK, true); + + /* Clear TIMER counter value */ + TIMER_CounterSet(US_TICKER_TIMER, 0); + + /* Get frequency of clock in MHz for scaling ticks to microseconds */ + ticker_freq_mhz = (REFERENCE_FREQUENCY / 1000000); + MBED_ASSERT(ticker_freq_mhz > 0); + + /* + * Calculate maximum prescaler that gives at least 1 MHz frequency, while keeping clock as an integer multiple of 1 MHz. + * Example: 14 MHz => prescaler = 1 (i.e. DIV2), ticker_freq_mhz = 7; + * 24 MHz => prescaler = 3 (i.e. DIV8), ticker_freq_mhz = 3; + * 48 MHz => prescaler = 4 (i.e. DIV16), ticker_freq_mhz = 3; + * Limit prescaling to maximum prescaler value, which is 10 (DIV1024). + */ + uint32_t prescaler = 0; + while((ticker_freq_mhz & 1) == 0 && prescaler <= 10) { + ticker_freq_mhz = ticker_freq_mhz >> 1; + prescaler++; + } + + /* Set prescaler */ + US_TICKER_TIMER->CTRL = (US_TICKER_TIMER->CTRL & ~_TIMER_CTRL_PRESC_MASK) | (prescaler << _TIMER_CTRL_PRESC_SHIFT); + + /* Select Compare Channel parameters */ + TIMER_InitCC_TypeDef timerCCInit = TIMER_INITCC_DEFAULT; + timerCCInit.mode = timerCCModeCompare; + + /* Configure Compare Channel 0 */ + TIMER_InitCC(US_TICKER_TIMER, 0, &timerCCInit); + + /* Enable interrupt vector in NVIC */ + TIMER_IntEnable(US_TICKER_TIMER, TIMER_IEN_OF); + NVIC_SetVector(US_TICKER_TIMER_IRQ, (uint32_t) us_ticker_irq_handler_internal); + NVIC_EnableIRQ(US_TICKER_TIMER_IRQ); + + /* Set top value */ + TIMER_TopSet(US_TICKER_TIMER, 0xFFFF); + + /* Start TIMER */ + TIMER_Enable(US_TICKER_TIMER, true); +} + +uint32_t us_ticker_read() +{ + uint32_t volatile countH_old, countH, countL; + + if (!us_ticker_inited) { + us_ticker_init(); + } + + /* Avoid jumping in time by reading high bits twice */ + do { + countH_old = ticker_cnt; + /* If the counter overflowed while in the IRQ handler for the CC0 interrupt, + * it hasn't had time to update ticker_cnt yet. Take this into account here. */ + if (TIMER_IntGet(US_TICKER_TIMER) & TIMER_IF_OF) { + countH_old += 1; + } + countL = US_TICKER_TIMER->CNT; + countH = ticker_cnt; + /* If the counter overflowed while in the IRQ handler for the CC0 interrupt, + * it hasn't had time to update ticker_cnt yet. Take this into account here. */ + if (TIMER_IntGet(US_TICKER_TIMER) & TIMER_IF_OF) { + countH += 1; + } + } while (countH_old != countH); + + /* Merge upper (mhz * 16-bit) and lower 16-bit into 64bit */ + uint64_t count = ((uint64_t)countH << 16) | (uint64_t)countL; + /* Divide by ticker_freq_mhz to get 32-bit 1MHz timestamp */ + return (count / ticker_freq_mhz); +} + +void us_ticker_set_interrupt(timestamp_t timestamp) +{ + int32_t delta = 0, ts = timestamp, time = us_ticker_read(); + + if((US_TICKER_TIMER->IEN & TIMER_IEN_CC0) == 0) { + //Timer was disabled, but is going to be enabled. Set sleep mode. + blockSleepMode(TIMER_LEAST_ACTIVE_SLEEPMODE); + } + TIMER_IntDisable(US_TICKER_TIMER, TIMER_IEN_CC0); + + delta = ts - time; + if(delta <= ticker_freq_mhz) { + delta = ticker_freq_mhz; + timestamp = us_ticker_read() + 0x100; + } + + /* Multiply by ticker_freq_mhz to get clock ticks */ + delta *= ticker_freq_mhz; + /* Overflowing this doesn't matter, since we only need the lower 16 bits */ + ts *= ticker_freq_mhz; + + /* Split delta between timers */ + ticker_int_cnt = (((uint64_t)delta) >> 16) & 0xFFFFFFFF; + ticker_int_rem = ts & 0xFFFF; + + /* Set compare channel 0 to (current position + lower 16 bits of delta). + * If lower 16 bits is a small number, we a do one compare of (current + lower 16 + 0x8000) + * and then one of (current + lower 16). Else, we simply use (current + lower 16). + * + * When time from lower 16 bits have elapsed, run complete cycles with ticker_int_rem as + * reference ticker_int_cnt times. */ + if ((delta & 0xFFFF) < 0x8000 && ticker_int_cnt > 0) { + TIMER_CompareSet(US_TICKER_TIMER, 0, ticker_int_rem + 0x8000); + ticker_int_cnt--; + } else { + TIMER_CompareSet(US_TICKER_TIMER, 0, ticker_int_rem); + ticker_int_rem = 0; + } + TIMER_IntClear(US_TICKER_TIMER, TIMER_IFC_CC0); + TIMER_IntEnable(US_TICKER_TIMER, TIMER_IEN_CC0); +} + +void us_ticker_disable_interrupt(void) +{ + if((US_TICKER_TIMER->IEN & TIMER_IEN_CC0) != 0) { + //Timer was enabled, but is going to get disabled. Clear sleepmode. + unblockSleepMode(TIMER_LEAST_ACTIVE_SLEEPMODE); + } + /* Disable compare channel interrupts */ + TIMER_IntDisable(US_TICKER_TIMER, TIMER_IEN_CC0); +} + +void us_ticker_clear_interrupt(void) +{ + /* Clear compare channel interrupts */ + TIMER_IntClear(US_TICKER_TIMER, TIMER_IFC_CC0); +}