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/gd32f470z_eval.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 we have a firmware file size limit of 171K.
See also https://www.gd32-dmx.org/bootloader.html
File: spiflashinstall.h
# elif defined (BOARD_GD32F470Z_EVAL)
# define OFFSET_UIMAGE 0x008000 // 32K
# define FIRMWARE_MAX_SIZE (171 * 1024) // 171K
There is 171KB flash starting at 0x08008000
The change to be made in your build configuration is in the file gd32f470zk_flash.ld .
MEMORY
{
FLASH (rx) : ORIGIN = 0x08008000, LENGTH = 171K
TCMSRAM (rw) : ORIGIN = 0x10000000, LENGTH = 64K
RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 112K
RAM1 (xrw) : ORIGIN = 0x2001C000, LENGTH = 16K
RAM2 (xrw) : ORIGIN = 0x20020000, LENGTH = 64K
RAMADD (xrw) : ORIGIN = 0x20030000, LENGTH = 0K
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.