mirror of
https://github.com/phdlee/uvk5cec
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50 lines
1.3 KiB
C
50 lines
1.3 KiB
C
/* Copyright 2023 Dual Tachyon
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* https://github.com/DualTachyon
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "ARMCM0.h"
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#include "systick.h"
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#include "../misc.h"
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// 0x20000324
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static uint32_t gTickMultiplier;
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void SYSTICK_Init(void)
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{
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SysTick_Config(480000);
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gTickMultiplier = 48;
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}
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void SYSTICK_DelayUs(uint32_t Delay)
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{
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const uint32_t ticks = Delay * gTickMultiplier;
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uint32_t elapsed_ticks = 0;
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uint32_t Start = SysTick->LOAD;
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uint32_t Previous = SysTick->VAL;
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do {
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uint32_t Current;
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do {
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Current = SysTick->VAL;
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} while (Current == Previous);
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uint32_t Delta = ((Current < Previous) ? - Current : Start - Current);
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elapsed_ticks += Delta + Previous;
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Previous = Current;
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} while (elapsed_ticks < ticks);
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}
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