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getting_started.md

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Getting started

Hardware

Development board (a cheap blue pill clone with STM32F103C8)

blue pill photo

https://www.laskarduino.cz/bluepill-arm-stm32-stm32f103c8-vyvojova-deska/

Programming interface: ST-Link V2

stlink v2 photo

Dependencies

Install Debian 11 packages needed for development

sudo apt install openocd gdb-multiarch

Install rust if not present

https://www.rust-lang.org/tools/install

Install Rust target

rustup target install thumbv7m-none-eabi

Building

cargo build

Starting the debugger

Connet the ST Link debugger to the blue pill development board and to the computer using USB port. Pins used are as follows:

stlink v2 photo

Warning: always check the pin out - there are many cheap ST Link debuggers out there and even if they look the same, connertor pin signals may be absolutely different

STLink different pinouts

My chosen colors for signals are:

  • green: GND
  • yellow: SWCLK
  • orange: SWDIO
  • red: 3.3V

Open the debugger using STlink v 2

openocd -f interface/stlink.cfg -f target/stm32f1x.cfg

Note: on older debian 10 system, use interface/stlink-v2.cfg

If MCU has been detected successfully, openocd should print Info : stm32f1x.cpu: hardware has 6 breakpoints, 4 watchpoints. Now it is ready to accept GDB connection.

In case openocd returns an error

Warn : UNEXPECTED idcode: 0x2ba01477
Error: expected 1 of 1: 0x1ba01477

That means that you got one of those chinese STM32F030C8 clones instead of a genuine STM microcontroller. It should still work fine, but you need to edit /usr/share/openocd/scripts/target/stm32f1x.cfg and replace set _CPUTAPID 0x1ba01477 with set _CPUTAPID 0x2ba01477

In case openocd prints

Info : Previous state query failed, trying to reconnect
Error: jtag status contains invalid mode value - communication failure
Polling target stm32f1x.cpu failed, trying to reexamine
Examination failed, GDB will be halted. Polling again in 700ms

Start openocd with reset button active

Cargo and linker configuration

Source codes already contain following files needed to compile and run the project

memory.x - defines microcontroller Flash and RAM size

/* Linker script for the STM32F103C8T6 */
MEMORY
{
  FLASH : ORIGIN = 0x08000000, LENGTH = 64K
  RAM : ORIGIN = 0x20000000, LENGTH = 20K
}

.cargo/config - tells Cargo to build for thumbv7m-none-eabi architecture and use gdb-multiarch for debugging

[target.thumbv7m-none-eabi]
runner = 'gdb-multiarch'
rustflags = [
  "-C", "link-arg=-Tlink.x",
]

[build]
target = "thumbv7m-none-eabi"

Running

Enable loading .gdbinit

echo "set auto-load safe-path $(pwd)" >> ~/.gdbinit

Running the program - blinking demo with semihosting debug output, but would not run without the debugger

cargo run --bin demo-blinky-semihosting

Green LED should start flashing, 1 second ON, 1 second OFF

Blinking LED

openocd console should show the following output at the same time:

OFF
ON
OFF
ON
OFF
ON
OFF

There is also standalone blinking demo that runs without active debug session, but does not have any semihosting output

cargo run --bin demo-blinky-standalone

Flashing

Install cargo flash program

cargo install cargo-flash

Note: When you see Unable to find libusb-1.0:, you may need to install libusb 1.0 development package as well: sudo apt install libusb-1.0-0-dev

Flash the program

cd demo-blinky-standalone
cargo flash --chip stm32f103C8 --release

Note: If you see Error Failed to open the debug probe, you have to close the running openocd session first.

Semihosting

Dependencies cortex-m-semihosting and panic-semihosting enable sending any debug prints and panic assertions into openocd console via STLink

Use either use panic_semihosting as _; or use panic_halt as _;