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