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80 lines
2.3 KiB
C
80 lines
2.3 KiB
C
/*
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* Copyright (C) 2020 Koen Zandberg
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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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* @defgroup sys_stdio_semihosting STDIO over Semihosting
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* @ingroup sys_stdio
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*
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* @brief Standard input/output backend using ARM Semihosting
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*
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* The ARM Semihosting provides an STDIO backend using the ARM Semihosting
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* protocol. The main advantage of Semihosting is that is allows STDIO over the
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* SWD/JTAG debugging interface already available on ARM microcontrollers.
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*
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* ARM Semihosting works by using the breakpoint instructing to trigger the
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* debugger to read the output or to write the input chars. Please be aware that
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* this might skew the timing of your application.
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*
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* The main disadvantage of Semihosting is that it is relative slow (even when
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* compared to serial uart), and that it requires an active debug session to
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* handle the breakpoint instructions. Without an active debug session the CPU
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* will halt on the first STDIO activity until the breakpoint is handled by the
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* debugger. Don't forget to disable the Semihosting module or replace it with
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* stdio_null when switching to production builds.
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*
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* As this is an ARM specific protocol, this module will only work on ARM-based
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* microcontrollers.
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*
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* ## Usage
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*
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* Enable Semihosting-based stdio by adding the following module to your
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* makefile:
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*
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* ```
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* USEMODULE += stdio_semihosting
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* ```
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*
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* If semihosting is not the default stdio mechanism of your board, the
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* `RIOT_TERMINAL` variable has to be set to `semihosting`:
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*
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* ```
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* make term RIOT_TERMINAL=semihosting
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* ```
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*
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* Launching the terminal will start an OpenOCD session with semihosting
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* enabled. This can be used for both STDIO interaction and for debugging the
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* firmware.
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*
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* @{
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* @file
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*
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* @author Koen Zandberg <koen@bergzand.net>
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*/
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#ifndef STDIO_SEMIHOSTING_H
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#define STDIO_SEMIHOSTING_H
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#include "stdio_base.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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* @brief Enable reception for Semihosting
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*
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* Automatically enabled when including the `stdin` module
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*/
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#define STDIO_SEMIHOSTING_RX (IS_USED(MODULE_STDIN))
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#ifdef __cplusplus
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}
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#endif
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/** @} */
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#endif /* STDIO_SEMIHOSTING_H */
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