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30 lines
1.3 KiB
C
30 lines
1.3 KiB
C
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// Copyright (c) 2023 Cesanta Software Limited
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// All rights reserved
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//
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// This file contains essentials required by the CMSIS:
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// uint32_t SystemCoreClock - holds the system core clock value
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// SystemInit() - initialises the system, e.g. sets up clocks
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#include "hal.h"
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uint32_t SystemCoreClock = SYS_FREQUENCY;
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void SystemInit(void) { // Called automatically by startup code
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SCB->CPACR |= ((3UL << 10 * 2) | (3UL << 11 * 2)); // Enable FPU
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asm("DSB");
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asm("ISB");
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FLASH->ACR |= FLASH_LATENCY | BIT(8) | BIT(9); // Flash latency, prefetch
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RCC->PLLCFGR &= ~((BIT(17) - 1)); // Clear PLL multipliers
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RCC->PLLCFGR |= (((PLL_P - 2) / 2) & 3) << 16; // Set PLL_P
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RCC->PLLCFGR |= PLL_M | (PLL_N << 6); // Set PLL_M and PLL_N
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RCC->CR |= BIT(24); // Enable PLL
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while ((RCC->CR & BIT(25)) == 0) spin(1); // Wait until done
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RCC->CFGR = (APB1_PRE << 10) | (APB2_PRE << 13); // Set prescalers
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RCC->CFGR |= 2; // Set clock source to PLL
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while ((RCC->CFGR & 12) == 0) spin(1); // Wait until done
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RCC->APB2ENR |= RCC_APB2ENR_SYSCFGEN; // Enable SYSCFG
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rng_init(); // Initialise random number generator
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SysTick_Config(SystemCoreClock / 1000); // Sys tick every 1ms
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}
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