86 lines
4.4 KiB

/* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <>.
/** USB DFU bootloader
* @file bootloader.c
* @author King Kévin <>
* @date 2017
/* standard libraries */
#include <stdint.h> // standard integer types
#include <stdbool.h> // boolean types
/* STM32 (including CM3) libraries */
#include <libopencm3/cm3/scb.h> // vector table definition
#include <libopencm3/stm32/rcc.h> // clock utilities
#include <libopencm3/stm32/gpio.h> // GPIO utilities
/* own libraries */
#include "global.h" // board definitions
#include "usb_dfu.h" // USB DFU utilities
/** bootloader entry point */
void main(void);
void main(void)
// check of DFU mode is forced
bool dfu_force = false; // to remember if DFU mode is forced
// check if a soft boot has been used
if (0==(RCC_CSR&0xfc000000)) { // no reset flag present -> this was a soft reset using csr_reset_core(), very probably to start the DFU mode
dfu_force = true;
} else { // check if the force DFU mode input is set
// disable SWJ pin to use as GPIO
gpio_primary_remap(AFIO_MAPR_SWJ_CFG_FULL_SWJ_NO_JNTRST, 0);
gpio_primary_remap(AFIO_MAPR_SWJ_CFG_JTAG_OFF_SW_ON, 0);
gpio_primary_remap(AFIO_MAPR_SWJ_CFG_JTAG_OFF_SW_OFF, 0);
rcc_periph_clock_enable(RCC_GPIO(DFU_FORCE_PORT)); // enable clock for GPIO domain
// pull on the opposite of the expected value
gpio_clear(GPIO(DFU_FORCE_PORT), GPIO(DFU_FORCE_PIN)); // pull down to be able to detect when tied to high
} else {
gpio_set(GPIO(DFU_FORCE_PORT), GPIO(DFU_FORCE_PIN)); // pull up to be able to detect when tied to low
if ((!DFU_FORCE_VALUE && 0==gpio_get(GPIO(DFU_FORCE_PORT), GPIO(DFU_FORCE_PIN))) || (DFU_FORCE_VALUE && 0!=gpio_get(GPIO(DFU_FORCE_PORT), GPIO(DFU_FORCE_PIN)))) { // check if output is set to the value to force DFU mode
dfu_force = true; // DFU mode forced
// start application if valid
/* 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
* on STM32F1xx SRAM begins at 0x2000 0000, and on STM32F103x8 there is 20KB of RAM (0x5000).
* since the stack grown "downwards" it should start at the end of the RAM: 0x2000 5000
* 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
volatile uint32_t* application = &__application_beginning; // get the value of the application address symbol (use a register instead on the stack since the stack pointer will be changed)
if (!dfu_force && (((*application)&0xFFFE0000)==0x20000000)) { // application at address seems valid
SCB_VTOR = (volatile uint32_t)(application); // set vector table to application vector table (store at the beginning of the application)
__asm__ volatile ("MSR msp,%0" : :"r"(*application)); // set stack pointer to address provided in the beginning of the application (loaded into a register first)
(*(void(**)(void))(application + 1))(); // start application (by jumping to the reset function which address is stored as second entry of the vector table)
rcc_clock_setup_in_hse_8mhz_out_72mhz(); // start main clock
board_setup(); // setup board to control LED
led_on(); // indicate bootloader started
usb_dfu_setup(); // setup USB DFU for firmware upload
usb_dfu_start(); // run DFU mode