This bootloader will install your application by means of the TFTP protocol. There is no need to change your application code. Per default DHCP is used for obtaining the ip-address.
The bootloader is active during reset of the board:
- Or when the
KEY_BOOTLOADER_TFTP_GPIO_PINxis pressed. Which is defined in filelib-gd32/include/board/gd32f450vi.h. - Or when
bkp_data_read(BKP_DATA_1) == 0xA5A5. This is set in your application by means of human readable UDP messages. See for more information: https://www.gd32-dmx.org/bootloader.html. There is also a sample Java UI application available for working with the UDP messages: https://github.com/vanvught/GD32F-Firmware-Update-UI
Otherwise the bootloader will directly jump to your application. With the snippet:
// 8. Call the reset handler
const uint32_t* reset_p = (uint32_t *)(FLASH_BASE + OFFSET_UIMAGE + 4);
asm volatile ("bx %0;" : : "r"(*reset_p));
The bootloader can be installed with the tools supplied by GigaDevice -> http://www.gd32mcu.com/en/download/7?kw=GD32F4
The limitation for the firmware file to be uploaded is given by the RAM available. With the 256K RAM (RAMADD) we have no firmware file size limit with the 224K avaiavle flashrom.
See also https://www.gd32-dmx.org/bootloader.html
File: spiflashinstall.h
# elif defined (BOARD_GD32F450VI)
# define OFFSET_UIMAGE 0x008000 // 32K
# define FIRMWARE_MAX_SIZE (224 * 1024) // 224K
# endif
There is just 224KB flash starting at 0x08008000
The change to be made in your build configuration is in the file gd32f450vi_flash.ld .
MEMORY
{
FLASH (rx) : ORIGIN = 0x08008000, LENGTH = 256K - 0x8000
TCMSRAM (rw) : ORIGIN = 0x10000000, LENGTH = 64K
RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 192K
RAMADD (xrw) : ORIGIN = 0x20030000, LENGTH = 256K
BKPSRAM (rw) : ORIGIN = 0x40024000, LENGTH = 4K
}
The FLASH ORIGIN must match the OFFSET_UIMAGE from the bootloader file spiflashinstall.h
The code for the bootloader is a fork from https://github.com/vanvught/rpidmx512. In order to reduce the memory footprint, some functions are not available.