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/**
* \file
* \brief USB DFU bootloader implementation (DFU mode)
*
* Copyright (c) 2018-2019 sysmocom -s.f.m.c. GmbH, Author: Kevin Redon <kredon@sysmocom.de>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "atmel_start.h"
#include "atmel_start_pins.h"
/** Start address of the application in flash
* \remark must be initialized by check_bootloader
*/
static uint32_t* application_start_address;
/** Check if the bootloader is valid
* \return true if the bootloader is valid and can be run
* \remark initializes application_start_address
*/
static bool check_bootloader(void)
{
if (hri_nvmctrl_read_STATUS_BOOTPROT_bf(FLASH_0.dev.hw) > 15) { // ensure BOOTPROT setting is valid
return false;
}
application_start_address = (uint32_t*)((15 - hri_nvmctrl_read_STATUS_BOOTPROT_bf(FLASH_0.dev.hw)) * 8192); // calculate bootloader size to know start address of the application (e.g. after the bootloader)
if (0 == application_start_address) { // no space has been reserved for the bootloader
return false;
}
return true;
}
/** Check if starting the bootloader is forced
* \return true of the DFU bootloader should be started
*/
static bool check_force_dfu(void)
{
gpio_set_pin_pull_mode(BUTTON_FORCE_DFU, GPIO_PULL_UP); // pull button high
return (0 == gpio_get_pin_level(BUTTON_FORCE_DFU)); // signal is low when button is pressed
}
/** Check if the application is valid
* \return true if the application is valid and can be started
* \warning application_start_address must be initialized
*/
static bool check_application(void)
{
/* the application starts with the vector table
* the first entry in the vector table is the initial stack pointer (SP) address
* the stack will be placed in RAM which begins at 0x2000 0000, and there is up to 256 KB of RAM (0x40000).
* if the SP is not in this range (e.g. flash has been erased) there is no valid application
* the second entry in the vector table is the reset address, corresponding to the application start
*/
return (0x20000000 == ((*application_start_address) & 0xFFF80000));
}
/** Start the application
* \warning application_start_address must be initialized
*/
static void start_application(void)
{
__set_MSP(*application_start_address); // re-base the Stack Pointer
SCB->VTOR = ((uint32_t) application_start_address & SCB_VTOR_TBLOFF_Msk); // re-base the vector table base address
asm("bx %0"::"r"(*(application_start_address + 1))); // jump to application Reset Handler in the application */
}
int main(void)
{
atmel_start_init(); // initialise system
if (!check_bootloader()) { // check bootloader
// blink the LED to tell the user we don't know where the application starts
while (true) {
gpio_set_pin_level(LED_SYSTEM, false);
delay_ms(500);
gpio_set_pin_level(LED_SYSTEM, true);
delay_ms(500);
}
}
if (!check_force_dfu() && check_application()) { // application is valid
start_application(); // start application
} else {
usb_dfu(); // start DFU bootloader
}
}
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