1.6 KiB
Game and Watch Test RAM Firmware
This is a minimal program designed to run in RAM on the STM32H7B0 chip inside of a Nintendo Game and Watch.
It is a starting point for playing with the platform without erasing its stock firmware.
Building and Running
To build the firmware image, just run make in this directory. You will need to have Make installed, along with the bare-metal ARM toolchain (arm-none-eabi-gcc).
The resulting main.elf file can be used by OpenOCD. Navigate to the openocd/ directory in this repository's top-level directory, and open a connection with your chosen debugger:
J-Link:
openocd -f jlink.cfg -c "transport select swd" -f stm32h7x_dual_bank.cfg -c "gdb_memory_map disable" -c init -c "arm semihosting enable" -c halt
ST-Link:
openocd -f stlink.cfg -f stm32h7x_dual_bank.cfg -c "gdb_memory_map disable"
In a separate terminal, open the compiled main.elf file in GDB:
arm-none-eabi-gdb main.elf
Connect to the OpenOCD interface on port 3333, and debug the program normally:
(gdb) target extended-remote :3333
Remote debugging using :3333
0xfffffffe in ?? ()
(gdb) load
Loading section .text, size 0x254 lma 0x0
Start address 0x134, load size 596
Transfer rate: 4768 bits in <1 sec, 596 bytes/write.
(gdb) bt
#0 reset_handler () at src/main.c:18
(gdb) c
Continuing.
^C
Program received signal SIGINT, Interrupt.
0x00000184 in main () at src/main.c:41
41 ++y;
(gdb) p y
$1 = 29431371
(gdb) p x
$2 = 42
From here, it shouldn't take too long to dump the contents of the SPI Flash chip (fingers crossed).