cm4bm

The ARM Cortex-M4 processor bare metal project with UART implementation

• Device: NUCLEO-F303ZE

Build

cm4bm dependents on some third-party packages to build code and burn into processor like ARM GNU Toolchain and stlink. Therefore, before using the project, we need to install these packages.

Install ARM GNU Toolchain:

$ sudo apt-get update
$ sudo apt-get -y install gcc-arm-none-eabi

Install stlink:

$ sudo apt-get update
$ sudo apt-get -y install stlink-tools

Install OpenOCD:

$ sudo apt install openocd

Build cm4bm:

$ make

Burn the code into processor:

$ make upload

Generate the disassembly file:

$ make disassembly

Debug

The toolchain downloaded using the command sudo apt-get -y install gcc-arm-none-eabi does not include arm-none-eabi-gdb. Therefore, it needs to be added separately, which can be downloaded from Arm GNU Toolchain Downloads. Then. adding arm-none-eabi-gdb into path /usr/bin/.

In cm4bm, it uses cortex-debug to trace the source code and find the bugs. Before using cortex-debug, the following libraries that are necessaty for arm-none-eabi-gdb need to be installed.

$ sudo apt-get install libncursesw5
$ sudo apt install python3.8

Test

Install putty to communicate with the board:

$ sudo apt-get install putty

GPIO setting

Set PD8 and PD9 as USART3 Tx and USART3 Rx respectively.

• PD8 setup:

  GPIO Setting	Mode
  GPIOD_MODE	Alternate function mode
  GPIOD_OSPEEDR	Low Speed
  GPIOD_PUPDR	No Pull-up & Pull-down
  GPIOD_OTYPER	Push-Pull
  GPIOD_AFRH	AF7 (USART3 Tx)

• PD9 setup:

  GPIO Setting	Mode
  GPIOD_MODE	Alternate function mode
  GPIOD_OSPEEDR	Low Speed
  GPIOD_PUPDR	No Pull-up & Pull-down
  GPIOD_OTYPER	Push-Pull
  GPIOD_AFRH	AF7 (USART3 Rx)

USART setup

USART3 config	Setting
F_CLK	8MHz (STM32F303ZE default clock)
USART3_Mode	Tx/Rx Enable
USART3_Parity	Parity disable
USART3_StopBits	1
USART3_WordLen	8
USART3_Baud	38400
USART3_HW_FLOW	None
Oversampling	16

Reference

• First time to use ARM Cortex-M4
• STM32F303xB/C/D/E, STM32F303x6/8, STM32F328x8, STM32F358xC, STM32F398xE Reference manual
• Cortex-M4 Technical Reference Manual
• ARM® v7-M Architecture Reference Manual