How to use the command 'st-flash' (with examples)

The st-flash command is a versatile tool designed to facilitate communication with and programming of STM32 ARM Cortex microcontrollers. It is particularly useful for developers and engineers working with embedded systems, enabling them to flash, read, and erase binary files directly on the microcontroller. This utility is part of the stlink suite, which provides open-source utilities to communicate with STM32 chips via the ST-Link programmer/debugger. Whether you’re updating firmware, debugging, testing, or simply maintaining an STM32-based device, st-flash plays a crucial role in your workflow.

Use Case 1: Reading from the Device

Code:

st-flash read firmware.bin 0x8000000 4096

Motivation:

The primary motivation behind reading from a device using st-flash is to retrieve the current state of the firmware or specific data located in the microcontroller’s memory. This is especially important in scenarios where a backup of the current firmware is needed before making any updates or modifications. It is also useful for verifying the contents of the device to ensure they match expected configurations or for setting a baseline before proceeding with development changes.

Explanation:

• read: This argument initiates the read operation from the device. It tells the st-flash tool that the subsequent file and address specify a memory region to be read.
• firmware.bin: This filename is where the read operation will save the data. The contents read from the device memory will be written into this file, serving as a backup or verification sample.
• 0x8000000: This parameter specifies the starting address in the device’s memory from which the reading begins. The hexadecimal address corresponds to the memory location on the STM32 microcontroller’s flash where the main application typically resides.
• 4096: This specifies the number of bytes to read from the specified memory location. Here, 4096 bytes, equivalent to 4 kilobytes, are read starting from the provided address.

Example Output:

2023-01-01T12:00:00 INFO common.c: Loading device parameters....
2023-01-01T12:00:01 INFO common.c: Device ID is 0x0418
2023-01-01T12:00:01 INFO common.c: SRAM size: 0x3000 bytes (12 KiB), Flash size: 0x10000 bytes (64 KiB) in pages of 1024 bytes
2023-01-01T12:00:01 INFO common.c: Reading 4096 bytes from address 0x08000000...
2023-01-01T12:00:02 INFO common.c: Successfully saved 4096 bytes to firmware.bin

Use Case 2: Writing to the Device

Code:

st-flash write firmware.bin 0x8000000

Motivation:

Writing new firmware to a microcontroller is a fundamental task in embedded systems development. This action updates the device’s software to a new version, applies critical patches, or loads a completely new application. Engineers and developers frequently use this functionality when transitioning between different phases of development, conducting tests, or deploying updates to ensure optimal performance and security enhancements.

Explanation:

• write: This argument specifies that the command will write data to the device. It initiates the operation to transfer binary data from your local system to the target microcontroller.
• firmware.bin: This is the file that contains the firmware data to be transferred. It should be a binary file formatted correctly for the target MCU and typically represents precompiled software ready for deployment.
• 0x8000000: This address designates the starting point in the device’s flash memory where the firmware will be written. This location typically marks the beginning of an STM32 application’s memory space, consistent with the device’s architecture.

Example Output:

2023-01-01T12:00:00 INFO common.c: Loading device parameters....
2023-01-01T12:00:01 INFO common.c: Device ID is 0x0418
2023-01-01T12:00:01 INFO common.c: SRAM size: 0x3000 bytes (12 KiB), Flash size: 0x10000 bytes (64 KiB) in pages of 1024 bytes
2023-01-01T12:00:01 INFO common.c: Writing 64 KiB to address 0x08000000...
2023-01-01T12:00:04 INFO common.c: Flash written and verified! jolly good!

Use Case 3: Erasing the Device

Code:

st-flash erase

Motivation:

Erasing the firmware from a device is often a preparatory step before writing new data. It ensures that no residual data conflicts with the new firmware being uploaded and is essential for maintaining the integrity of the device’s operations. Additionally, developers may use this functionality to completely reset a device to a clean state when troubleshooting issues or when decommissioning devices.

Explanation:

• erase: This command deletes all the existing firmware and data on the microcontroller’s flash memory. It initiates a flash erase cycle that clears the current contents to ensure that no remnants of previous data remain.

Example Output:

2023-01-01T12:00:00 INFO common.c: Loading device parameters....
2023-01-01T12:00:01 INFO common.c: Device ID is 0x0418
2023-01-01T12:00:01 INFO common.c: SRAM size: 0x3000 bytes (12 KiB), Flash size: 0x10000 bytes (64 KiB) in pages of 1024 bytes
2023-01-01T12:00:01 INFO common.c: Erasing flash...
2023-01-01T12:00:02 INFO common.c: Flash erased successfully!

Conclusion:

The st-flash command is an invaluable tool for working with STM32 microcontrollers, providing essential functionality for reading, writing, and erasing firmware. Understanding and utilizing each of these commands ensures effective management and control over the microcontroller’s memory, facilitating a wide range of applications and development processes in embedded systems. These capabilities combine to offer robust support for both development and operational maintenance in technology relying on STM32 microcontroller platforms.