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The ATmega328p on a breadboard can have various frequencies depending on the fuse settings and whether and which crystal is connected. Thus, finding a fixed xtimer frequency that can be configured for every CPU core clock with the available prescalers is not possible. Therefore, the fixed frequency is replaced by a frequency depending on the CPU clock speed. For CPU clock frequency of more than 4 MHz a prescaler of 64 will be chosen (same as on the Arduino Uno), for 4 MHz and less a prescaler of 8 will be chosen.
67 lines
1.5 KiB
C
67 lines
1.5 KiB
C
/*
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* Copyright (C) 2014 Freie Universität Berlin, Hinnerk van Bruinehsen
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* 2016 Laurent Navet <laurent.navet@gmail.com>
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* 2019 Otto-von-Guericke-Universität Magdeburg
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @ingroup boards_atmega328p
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* @{
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*
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* @file
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* @brief Board specific definitions for the standalone ATmega328p "board"
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*
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* @author Marian Buschsieweke <marian.buschsieweke@ovgu.de>
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* @author Hinnerk van Bruinehsen <h.v.bruinehsen@fu-berlin.de>
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* @author Laurent Navet <laurent.navet@gmail.com>
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*/
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#ifndef BOARD_H
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#define BOARD_H
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#include "cpu.h"
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#include "periph_conf.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* @name STDIO configuration
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*
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* As the CPU is too slow to handle 115200 baud, we set the default
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* baudrate to 9600 for this board
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* @{
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*/
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#define STDIO_UART_BAUDRATE (9600U)
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/** @} */
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/**
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* @name xtimer configuration values
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* @{
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*/
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#define XTIMER_WIDTH (16)
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#if CLOCK_CORECLOCK > 4000000UL
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#define XTIMER_HZ (CLOCK_CORECLOCK / 64)
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#else
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#define XTIMER_HZ (CLOCK_CORECLOCK / 8)
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#endif
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#define XTIMER_BACKOFF (40)
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/** @} */
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/**
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* @brief Initialize board specific hardware, including clock, LEDs and std-IO
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*/
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void board_init(void);
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#ifdef __cplusplus
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}
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#endif
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#endif /* BOARD_H */
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/** @} */
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