Amit Gandhi / mbed-dev

test

Fork of mbed-dev by mbed official

targets/TARGET_STM/us_ticker_16b.c@175:b96e65c34a4d, 2017-10-02 (annotated)

Committer:
AnnaBridge
Date:
Mon Oct 02 15:33:19 2017 +0100
Revision:
175:b96e65c34a4d
Parent:
168:e84263d55307 
This updates the lib to the mbed lib v 152

Who changed what in which revision?

UserRevisionLine numberNew contents of line
<> 153:fa9ff456f731 1 /* mbed Microcontroller Library
<> 153:fa9ff456f731 2 * Copyright (c) 2006-2016 ARM Limited
<> 153:fa9ff456f731 3 *
<> 153:fa9ff456f731 4 * Licensed under the Apache License, Version 2.0 (the "License");
<> 153:fa9ff456f731 5 * you may not use this file except in compliance with the License.
<> 153:fa9ff456f731 6 * You may obtain a copy of the License at
<> 153:fa9ff456f731 7 *
<> 153:fa9ff456f731 8 * http://www.apache.org/licenses/LICENSE-2.0
<> 153:fa9ff456f731 9 *
<> 153:fa9ff456f731 10 * Unless required by applicable law or agreed to in writing, software
<> 153:fa9ff456f731 11 * distributed under the License is distributed on an "AS IS" BASIS,
<> 153:fa9ff456f731 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
<> 153:fa9ff456f731 13 * See the License for the specific language governing permissions and
<> 153:fa9ff456f731 14 * limitations under the License.
<> 153:fa9ff456f731 15 */
<> 153:fa9ff456f731 16 #include <stddef.h>
<> 153:fa9ff456f731 17 #include "us_ticker_api.h"
<> 153:fa9ff456f731 18 #include "PeripheralNames.h"
<> 153:fa9ff456f731 19 #include "hal_tick.h"
<> 153:fa9ff456f731 20
<> 153:fa9ff456f731 21 // A 16-bit timer is used
<> 153:fa9ff456f731 22 #if TIM_MST_16BIT
<> 153:fa9ff456f731 23
<> 153:fa9ff456f731 24 TIM_HandleTypeDef TimMasterHandle;
<> 153:fa9ff456f731 25
<> 153:fa9ff456f731 26 volatile uint32_t SlaveCounter = 0;
<> 153:fa9ff456f731 27 volatile uint32_t oc_int_part = 0;
<> 153:fa9ff456f731 28
<> 153:fa9ff456f731 29 void us_ticker_init(void)
<> 153:fa9ff456f731 30 {
AnnaBridge 175:b96e65c34a4d 31 /* NOTE: assuming that HAL tick has already been initialized! */
<> 153:fa9ff456f731 32 }
<> 153:fa9ff456f731 33
<> 153:fa9ff456f731 34 uint32_t us_ticker_read()
<> 153:fa9ff456f731 35 {
<> 153:fa9ff456f731 36 uint16_t cntH_old, cntH, cntL;
<> 153:fa9ff456f731 37 do {
<> 153:fa9ff456f731 38 cntH_old = SlaveCounter;
AnnaBridge 168:e84263d55307 39 /* SlaveCounter needs to be checked before AND after we read the
AnnaBridge 168:e84263d55307 40 * current counter TIM_MST->CNT, in case it wraps around.
AnnaBridge 168:e84263d55307 41 * there are 2 possible cases of wrap around
AnnaBridge 168:e84263d55307 42 * 1) in case this function is interrupted by timer_irq_handler and
AnnaBridge 168:e84263d55307 43 * the SlaveCounter is updated. In that case we will loop again.
AnnaBridge 168:e84263d55307 44 * 2) in case this function is called from interrupt context during
AnnaBridge 168:e84263d55307 45 * wrap-around condtion. That would prevent/delay the timer_irq_handler
AnnaBridge 168:e84263d55307 46 * from being called so we need to locally check the FLAG_UPDATE and
AnnaBridge 168:e84263d55307 47 * update the cntH accordingly. The SlaveCounter variable itself will
AnnaBridge 168:e84263d55307 48 * be updated in the interrupt handler just after ...
AnnaBridge 168:e84263d55307 49 */
<> 153:fa9ff456f731 50 if (__HAL_TIM_GET_FLAG(&TimMasterHandle, TIM_FLAG_UPDATE) == SET) {
<> 153:fa9ff456f731 51 cntH_old += 1;
<> 153:fa9ff456f731 52 }
<> 153:fa9ff456f731 53 cntL = TIM_MST->CNT;
<> 153:fa9ff456f731 54 cntH = SlaveCounter;
<> 153:fa9ff456f731 55 if (__HAL_TIM_GET_FLAG(&TimMasterHandle, TIM_FLAG_UPDATE) == SET) {
<> 153:fa9ff456f731 56 cntH += 1;
<> 153:fa9ff456f731 57 }
<> 153:fa9ff456f731 58 } while(cntH_old != cntH);
<> 153:fa9ff456f731 59 // Glue the upper and lower part together to get a 32 bit timer
<> 153:fa9ff456f731 60 return (uint32_t)(cntH << 16 | cntL);
<> 153:fa9ff456f731 61 }
<> 153:fa9ff456f731 62
<> 153:fa9ff456f731 63 void us_ticker_set_interrupt(timestamp_t timestamp)
<> 153:fa9ff456f731 64 {
AnnaBridge 168:e84263d55307 65 // NOTE: This function must be called with interrupts disabled to keep our
AnnaBridge 168:e84263d55307 66 // timer interrupt setup atomic
AnnaBridge 175:b96e65c34a4d 67
AnnaBridge 168:e84263d55307 68 // Set new output compare value
AnnaBridge 168:e84263d55307 69 __HAL_TIM_SET_COMPARE(&TimMasterHandle, TIM_CHANNEL_1, timestamp & 0xFFFF);
AnnaBridge 168:e84263d55307 70 // Ensure the compare event starts clear
AnnaBridge 168:e84263d55307 71 __HAL_TIM_CLEAR_FLAG(&TimMasterHandle, TIM_FLAG_CC1);
AnnaBridge 168:e84263d55307 72 // Enable IT
AnnaBridge 168:e84263d55307 73 __HAL_TIM_ENABLE_IT(&TimMasterHandle, TIM_IT_CC1);
<> 153:fa9ff456f731 74
AnnaBridge 175:b96e65c34a4d 75 /* Set the number of timer wrap-around loops before the actual timestamp
AnnaBridge 175:b96e65c34a4d 76 * is reached. If the calculated delta time is more than halfway to the
AnnaBridge 175:b96e65c34a4d 77 * next compare event, check to see if a compare event has already been
AnnaBridge 175:b96e65c34a4d 78 * set, and if so, add one to the wrap-around count. This is done to
AnnaBridge 175:b96e65c34a4d 79 * ensure the correct wrap count is used in the corner cases where the
AnnaBridge 175:b96e65c34a4d 80 * 16 bit counter passes the compare value during the process of
AnnaBridge 175:b96e65c34a4d 81 * configuring this interrupt.
AnnaBridge 175:b96e65c34a4d 82 *
AnnaBridge 175:b96e65c34a4d 83 * Assumption: The time to execute this function is less than 32ms
AnnaBridge 175:b96e65c34a4d 84 * (otherwise incorrect behaviour could result)
AnnaBridge 175:b96e65c34a4d 85 *
AnnaBridge 175:b96e65c34a4d 86 * Consider the following corner cases:
AnnaBridge 175:b96e65c34a4d 87 * 1) timestamp is 1 us in the future:
AnnaBridge 175:b96e65c34a4d 88 * oc_int_part = 0 initially
AnnaBridge 175:b96e65c34a4d 89 * oc_int_part left at 0 because ((delta - 1) & 0xFFFF) < 0x8000
AnnaBridge 175:b96e65c34a4d 90 * Compare event should happen in 1 us and us_ticker_irq_handler()
AnnaBridge 175:b96e65c34a4d 91 * called
AnnaBridge 175:b96e65c34a4d 92 * 2) timestamp is 0x8000 us in the future:
AnnaBridge 175:b96e65c34a4d 93 * oc_int_part = 0 initially
AnnaBridge 175:b96e65c34a4d 94 * oc_int_part left at 0 because ((delta - 1) & 0xFFFF) < 0x8000
AnnaBridge 175:b96e65c34a4d 95 * There should be no possibility of the CC1 flag being set yet
AnnaBridge 175:b96e65c34a4d 96 * (see assumption above). When the compare event does occur in
AnnaBridge 175:b96e65c34a4d 97 * 32768 us, us_ticker_irq_handler() will be called
AnnaBridge 175:b96e65c34a4d 98 * 3) timestamp is 0x8001 us in the future:
AnnaBridge 175:b96e65c34a4d 99 * oc_int_part = 0 initially
AnnaBridge 175:b96e65c34a4d 100 * ((delta - 1) & 0xFFFF) >= 0x8000 but there should be no
AnnaBridge 175:b96e65c34a4d 101 * possibility of the CC1 flag being set yet (see assumption above),
AnnaBridge 175:b96e65c34a4d 102 * so oc_int_part will be left at 0, and when the compare event
AnnaBridge 175:b96e65c34a4d 103 * does occur in 32769 us, us_ticker_irq_handler() will be called
AnnaBridge 175:b96e65c34a4d 104 * 4) timestamp is 0x10000 us in the future:
AnnaBridge 175:b96e65c34a4d 105 * oc_int_part = 0 initially
AnnaBridge 175:b96e65c34a4d 106 * ((delta - 1) & 0xFFFF) >= 0x8000
AnnaBridge 175:b96e65c34a4d 107 * There are two subcases:
AnnaBridge 175:b96e65c34a4d 108 * a) The timer counter has not incremented past the compare
AnnaBridge 175:b96e65c34a4d 109 * value while setting up the interrupt. In this case, the
AnnaBridge 175:b96e65c34a4d 110 * CC1 flag will not be set, so oc_int_part will be
AnnaBridge 175:b96e65c34a4d 111 * left at 0, and when the compare event occurs in 65536 us,
AnnaBridge 175:b96e65c34a4d 112 * us_ticker_irq_handler() will be called
AnnaBridge 175:b96e65c34a4d 113 * b) The timer counter has JUST incremented past the compare
AnnaBridge 175:b96e65c34a4d 114 * value. In this case, the CC1 flag will be set, so
AnnaBridge 175:b96e65c34a4d 115 * oc_int_part will be incremented to 1, and the interrupt will
AnnaBridge 175:b96e65c34a4d 116 * occur immediately after this function returns, where
AnnaBridge 175:b96e65c34a4d 117 * oc_int_part will decrement to 0 without calling
AnnaBridge 175:b96e65c34a4d 118 * us_ticker_irq_handler(). Then about 65536 us later, the
AnnaBridge 175:b96e65c34a4d 119 * compare event will occur again, and us_ticker_irq_handler()
AnnaBridge 175:b96e65c34a4d 120 * will be called
AnnaBridge 175:b96e65c34a4d 121 * 5) timestamp is 0x10001 us in the future:
AnnaBridge 175:b96e65c34a4d 122 * oc_int_part = 1 initially
AnnaBridge 175:b96e65c34a4d 123 * oc_int_part left at 1 because ((delta - 1) & 0xFFFF) < 0x8000
AnnaBridge 175:b96e65c34a4d 124 * CC1 flag will not be set (see assumption above). In 1 us the
AnnaBridge 175:b96e65c34a4d 125 * compare event will cause an interrupt, where oc_int_part will be
AnnaBridge 175:b96e65c34a4d 126 * decremented to 0 without calling us_ticker_irq_handler(). Then
AnnaBridge 175:b96e65c34a4d 127 * about 65536 us later, the compare event will occur again, and
AnnaBridge 175:b96e65c34a4d 128 * us_ticker_irq_handler() will be called
AnnaBridge 175:b96e65c34a4d 129 * 6) timestamp is 0x18000 us in the future:
AnnaBridge 175:b96e65c34a4d 130 * oc_int_part = 1 initially
AnnaBridge 175:b96e65c34a4d 131 * oc_int_part left at 1 because ((delta - 1) & 0xFFFF) < 0x8000
AnnaBridge 175:b96e65c34a4d 132 * There should be no possibility of the CC1 flag being set yet
AnnaBridge 175:b96e65c34a4d 133 * (see assumption above). When the compare event does occur in
AnnaBridge 175:b96e65c34a4d 134 * 32768 us, oc_int_part will be decremented to 0 without calling
AnnaBridge 175:b96e65c34a4d 135 * us_ticker_irq_handler(). Then about 65536 us later, the
AnnaBridge 175:b96e65c34a4d 136 * compare event will occur again, and us_ticker_irq_handler() will
AnnaBridge 175:b96e65c34a4d 137 * be called
AnnaBridge 175:b96e65c34a4d 138 * 7) timestamp is 0x18001 us in the future:
AnnaBridge 175:b96e65c34a4d 139 * oc_int_part = 1 initially
AnnaBridge 175:b96e65c34a4d 140 * ((delta - 1) & 0xFFFF) >= 0x8000 but there should be no
AnnaBridge 175:b96e65c34a4d 141 * possibility of the CC1 flag being set yet (see assumption above),
AnnaBridge 175:b96e65c34a4d 142 * so oc_int_part will be left at 1, and when the compare event
AnnaBridge 175:b96e65c34a4d 143 * does occur in 32769 us, oc_int_part will be decremented to 0
AnnaBridge 175:b96e65c34a4d 144 * without calling us_ticker_irq_handler(). Then about 65536 us
AnnaBridge 175:b96e65c34a4d 145 * later, the compare event will occur again, and
AnnaBridge 175:b96e65c34a4d 146 * us_ticker_irq_handler() will be called
AnnaBridge 175:b96e65c34a4d 147 *
AnnaBridge 175:b96e65c34a4d 148 * delta - 1 is used because the timer compare event happens on the
AnnaBridge 175:b96e65c34a4d 149 * counter incrementing to match the compare value, and it won't occur
AnnaBridge 175:b96e65c34a4d 150 * immediately when the compare value is set to the current counter
AnnaBridge 175:b96e65c34a4d 151 * value.
AnnaBridge 175:b96e65c34a4d 152 */
AnnaBridge 175:b96e65c34a4d 153 uint32_t current_time = us_ticker_read();
AnnaBridge 175:b96e65c34a4d 154 uint32_t delta = timestamp - current_time;
AnnaBridge 175:b96e65c34a4d 155 /* Note: The case of delta <= 0 is handled in MBED upper layer */
AnnaBridge 175:b96e65c34a4d 156 oc_int_part = (delta - 1) >> 16;
AnnaBridge 175:b96e65c34a4d 157 if ( ((delta - 1) & 0xFFFF) >= 0x8000 &&
AnnaBridge 175:b96e65c34a4d 158 __HAL_TIM_GET_FLAG(&TimMasterHandle, TIM_FLAG_CC1) == SET ) {
AnnaBridge 175:b96e65c34a4d 159 ++oc_int_part;
AnnaBridge 175:b96e65c34a4d 160 /* NOTE: Instead of incrementing oc_int_part here, we could clear
AnnaBridge 175:b96e65c34a4d 161 * the CC1 flag, but then you'd have to wait to ensure the
AnnaBridge 175:b96e65c34a4d 162 * interrupt is knocked down before returning and reenabling
AnnaBridge 175:b96e65c34a4d 163 * interrupts. Since this is a rare case, it's not worth it
AnnaBridge 175:b96e65c34a4d 164 * to try and optimize it, and it keeps the code simpler and
AnnaBridge 175:b96e65c34a4d 165 * safer to just do this increment instead.
AnnaBridge 168:e84263d55307 166 */
<> 153:fa9ff456f731 167 }
AnnaBridge 175:b96e65c34a4d 168
<> 153:fa9ff456f731 169 }
<> 153:fa9ff456f731 170
AnnaBridge 175:b96e65c34a4d 171 void us_ticker_fire_interrupt(void)
AnnaBridge 175:b96e65c34a4d 172 {
AnnaBridge 175:b96e65c34a4d 173 /* When firing the event, the number of 16 bits counter wrap-ups (oc_int)
AnnaBridge 175:b96e65c34a4d 174 * must be re-initialized */
AnnaBridge 175:b96e65c34a4d 175 oc_int_part = 0;
AnnaBridge 175:b96e65c34a4d 176 HAL_TIM_GenerateEvent(&TimMasterHandle, TIM_EVENTSOURCE_CC1);
AnnaBridge 175:b96e65c34a4d 177 }
AnnaBridge 175:b96e65c34a4d 178
AnnaBridge 175:b96e65c34a4d 179 /* NOTE: must be called with interrupts disabled! */
<> 153:fa9ff456f731 180 void us_ticker_disable_interrupt(void)
<> 153:fa9ff456f731 181 {
<> 153:fa9ff456f731 182 __HAL_TIM_DISABLE_IT(&TimMasterHandle, TIM_IT_CC1);
<> 153:fa9ff456f731 183 }
<> 153:fa9ff456f731 184
AnnaBridge 175:b96e65c34a4d 185 /* NOTE: must be called with interrupts disabled! */
<> 153:fa9ff456f731 186 void us_ticker_clear_interrupt(void)
<> 153:fa9ff456f731 187 {
AnnaBridge 168:e84263d55307 188 __HAL_TIM_CLEAR_FLAG(&TimMasterHandle, TIM_FLAG_CC1);
<> 153:fa9ff456f731 189 }
<> 153:fa9ff456f731 190
<> 153:fa9ff456f731 191 #endif // TIM_MST_16BIT