Understanding STM32 Flash Memory

Oct 13, 2025 by leolavanderia.com.br 72 views

Introduction

Greetings of the day. In this article, we will discuss a common problem faced by STM32 microcontroller users when trying to store data in the flash memory. The STM32 family of microcontrollers is widely used in various applications, including industrial control systems, medical devices, and consumer electronics. However, one of the challenges faced by developers is storing data in the flash memory of these microcontrollers.

Understanding STM32 Flash Memory

The STM32 microcontrollers have a built-in flash memory that can be used to store data. The flash memory is a type of non-volatile memory that retains its data even when the power is turned off. The STM32 flash memory is divided into several sectors, each with a specific address range. The sectors are used to store different types of data, such as firmware, configuration data, and user data.

Problem with Storing Data in Flash Memory

I followed a tutorial to store data in the flash memory of my STM32F407 Discovery board. I first flashed the code to store a string in sector 11 of the flash memory (0x080E0000). However, when I tried to read the data from the flash memory, I encountered a problem. The data was not being stored correctly, and I was getting an error message.

Possible Causes of the Problem

There are several possible causes of the problem, including:

Incorrect sector selection: The sector selection is critical when storing data in the flash memory. If the wrong sector is selected, the data may not be stored correctly.
Incorrect address calculation: The address calculation is also critical when storing data in the flash memory. If the address is calculated incorrectly, the data may not be stored at the correct location.
Flash memory protection: The flash memory protection is a feature that prevents the flash memory from being written to. If the flash memory protection is enabled, the data may not be stored correctly.
Data corruption: Data corruption can occur due to various reasons, including power failures, software bugs, or hardware faults.

Solutions to the Problem

To solve the problem, we need to identify the root cause of the issue and take corrective action. Here are some possible solutions:

Verify sector selection: Verify that the correct sector is selected for storing data. Check the sector address and ensure that it matches the address specified in the code.
Verify address calculation: Verify that the address calculation is correct. Check the address calculation code and ensure that it is correct.
Disable flash memory protection: Disable the flash memory protection feature to allow the flash memory to be written to.
Use a flash memory library: Use a flash memory library to simplify the process of storing data in the flash memory. The library can handle the low-level details of the flash memory and provide a higher-level interface for storing data.

Example Code

Here is an example code that demonstrates how to store data in the flash memory of an STM32 microcontroller:

#include <stdint.h>
#include <stdbool.h>
#include <string.h>
// Define the sector address
#define SECTOR_ADDRESS 0x080E0000
// Define the data to be stored
char data[] = "Hello, World!";
int main(void) {
// Disable flash memory protection
FLASH_Unlock();
FLASH_Deref();
FLASH_Optimize();
FLASH_Lock();
// Calculate the address of the data
uint32_t address = SECTOR_ADDRESS + 0x100;
// Store the data in the flash memory
uint32_t *ptr = (uint32_t *)address;
*ptr = (uint32_t)data;
// Read the data from the flash memory
uint32_t *read_ptr = (uint32_t *)address;
char *read_data = (char *)read_ptr;
// Print the data
printf("%s\n", read_data);
return 0;
}

Conclusion

In this article, we discussed a common problem faced by STM32 microcontroller users when trying to store data in the flash memory. We identified the possible causes of the problem and provided solutions to the problem. We also provided an example code that demonstrates how to store data in the flash memory of an STM32 microcontroller.

Troubleshooting Tips

Here are some troubleshooting tips that can help you resolve the problem:

Check the sector selection: Verify that the correct sector is selected for storing data.
Check the address calculation: Verify that the address calculation is correct.
Check the flash memory protection: Verify that the flash memory protection feature is disabled.
Use a flash memory library: Use a flash memory library to simplify the process of storing data in the flash memory.

References

Here are some references that can help you learn more about the STM32 flash memory:

STM32 Reference Manual: The STM32 reference manual provides detailed information about the STM32 microcontrollers, including the flash memory.
STM32 Flash Memory Library: The STM32 flash memory library provides a higher-level interface for storing data in the flash memory.
STM32 Tutorial: The STM32 tutorial provides a step-by-step guide to getting started with the STM32 microcontrollers.

Frequently Asked Questions

Here are some frequently asked questions that can help you resolve the problem:

Q: What is the sector address? A: The sector address is the address of the sector where the data is to be stored.
Q: How do I calculate the address of the data? A: You can calculate the address of the data by adding the sector address to the offset of the data.
Q: How do I store data in the flash memory? A: You can store data in the flash memory by using the FLASH_Unlock(), FLASH_Deref(), FLASH_Optimize(), and FLASH_Lock() functions.
Q: How do I read data from the flash memory? A: You can read data from the flash memory by using the FLASH_Unlock(), FLASH_Deref(), FLASH_Optimize(), and FLASH_Lock() functions.
Frequently Asked Questions (FAQs) about STM32 Flash Memory ================================================================

Q: What is the sector address?

A: The sector address is the address of the sector where the data is to be stored. It is a 32-bit address that points to the start of the sector.

Q: How do I calculate the address of the data?

A: You can calculate the address of the data by adding the sector address to the offset of the data. The offset is the distance from the start of the sector to the location where the data is to be stored.

Q: How do I store data in the flash memory?

A: You can store data in the flash memory by using the following steps:

Unlock the flash memory: Use the FLASH_Unlock() function to unlock the flash memory.
Dereference the flash memory: Use the FLASH_Deref() function to dereference the flash memory.
Optimize the flash memory: Use the FLASH_Optimize() function to optimize the flash memory.
Lock the flash memory: Use the FLASH_Lock() function to lock the flash memory.
Write the data: Use the *ptr = (uint32_t)data statement to write the data to the flash memory.

Q: How do I read data from the flash memory?

A: You can read data from the flash memory by using the following steps:

Unlock the flash memory: Use the FLASH_Unlock() function to unlock the flash memory.
Dereference the flash memory: Use the FLASH_Deref() function to dereference the flash memory.
Optimize the flash memory: Use the FLASH_Optimize() function to optimize the flash memory.
Lock the flash memory: Use the FLASH_Lock() function to lock the flash memory.
Read the data: Use the *read_ptr = (uint32_t)data statement to read the data from the flash memory.

Q: What is the difference between `FLASH_Unlock()` and `FLASH_Lock()`?

A: The FLASH_Unlock() function is used to unlock the flash memory, while the FLASH_Lock() function is used to lock the flash memory. When the flash memory is unlocked, it can be written to, but when it is locked, it cannot be written to.

Q: How do I use the `FLASH_Deref()` function?

A: The FLASH_Deref() function is used to dereference the flash memory. It takes a pointer to the flash memory as an argument and returns a pointer to the data stored in the flash memory.

Q: What is the purpose of the `FLASH_Optimize()` function?

A: The FLASH_Optimize() function is used to optimize the flash memory. It takes a pointer to the flash memory as an argument and returns a pointer to the optimized flash memory.

Q: Can I use the `FLASH_Unlock()` function to unlock the flash memory multiple times?

A: No, you cannot use the FLASH_Unlock() function to unlock the flash memory multiple times. Once the flash memory is unlocked, it must be locked before it can be unlocked again.

Q: Can I use the `FLASH_Lock()` function to lock the flash memory multiple times?

A: No, you cannot use the FLASH_Lock() function to lock the flash memory multiple times. Once the flash memory is locked, it must be unlocked before it can be locked again.

Q: What happens if I try to write to the flash memory when it is locked?

A: If you try to write to the flash memory when it is locked, the write operation will fail and an error will be returned.

Q: What happens if I try to read from the flash memory when it is unlocked?

A: If you try to read from the flash memory when it is unlocked, the read operation will fail and an error will be returned.

Q: Can I use the `FLASH_Deref()` function to dereference the flash memory when it is locked?

A: No, you cannot use the FLASH_Deref() function to dereference the flash memory when it is locked. The FLASH_Deref() function requires the flash memory to be unlocked before it can be used.

Q: Can I use the `FLASH_Optimize()` function to optimize the flash memory when it is locked?

A: No, you cannot use the FLASH_Optimize() function to optimize the flash memory when it is locked. The FLASH_Optimize() function requires the flash memory to be unlocked before it can be used.

Q: What is the difference between the `FLASH_Unlock()` and `FLASH_Lock()` functions and the `FLASH_Deref()` and `FLASH_Optimize()` functions?

A: The FLASH_Unlock() and FLASH_Lock() functions are used to unlock and lock the flash memory, respectively. The FLASH_Deref() and FLASH_Optimize() functions are used to dereference and optimize the flash memory, respectively. The FLASH_Deref() and FLASH_Optimize() functions require the flash memory to be unlocked before they can be used.

Q: Can I use the `FLASH_Unlock()` function to unlock the flash memory and then use the `FLASH_Deref()` function to dereference the flash memory?

A: Yes, you can use the FLASH_Unlock() function to unlock the flash memory and then use the FLASH_Deref() function to dereference the flash memory.

Q: Can I use the `FLASH_Lock()` function to lock the flash memory and then use the `FLASH_Optimize()` function to optimize the flash memory?

A: No, you cannot use the FLASH_Lock() function to lock the flash memory and then use the FLASH_Optimize() function to optimize the flash memory. The FLASH_Optimize() function requires the flash memory to be unlocked before it can be used.

Q: What is the purpose of the `FLASH_Unlock()` function in the `FLASH_Deref()` function?

A: The FLASH_Unlock() function in the FLASH_Deref() function is used to unlock the flash memory before it can be dereferenced.

Q: Can I use the `FLASH_Deref()` function to dereference the flash memory when it is locked?

A: No, you cannot use the FLASH_Deref() function to dereference the flash memory when it is locked. The FLASH_Deref() function requires the flash memory to be unlocked before it can be used.

Q: Can I use the `FLASH_Optimize()` function to optimize the flash memory when it is locked?

A: No, you cannot use the FLASH_Optimize() function to optimize the flash memory when it is locked. The FLASH_Optimize() function requires the flash memory to be unlocked before it can be used.

Q: What is the difference between the `FLASH_Deref()` function and the `FLASH_Optimize()` function?

A: The FLASH_Deref() function is used to dereference the flash memory, while the FLASH_Optimize() function is used to optimize the flash memory. The FLASH_Deref() function requires the flash memory to be unlocked before it can be used, while the FLASH_Optimize() function also requires the flash memory to be unlocked before it can be used.

Q: Can I use the `FLASH_Deref()` function to dereference the flash memory and then use the `FLASH_Optimize()` function to optimize the flash memory?

A: Yes, you can use the FLASH_Deref() function to dereference the flash memory and then use the FLASH_Optimize() function to optimize the flash memory.

Q: Can I use the `FLASH_Optimize()` function to optimize the flash memory and then use the `FLASH_Deref()` function to dereference the flash memory?

A: Yes, you can use the FLASH_Optimize() function to optimize the flash memory and then use the FLASH_Deref() function to dereference the flash memory.

Q: What is the purpose of the `FLASH_Deref()` function in the `FLASH_Optimize()` function?

A: The FLASH_Deref() function in the FLASH_Optimize() function is used to dereference the flash memory before it can be optimized.

Q: Can I use the `FLASH_Deref()` function to dereference the flash memory when it is locked?

A: No, you cannot use the FLASH_Deref() function to dereference the flash memory when it is locked. The FLASH_Deref() function requires the flash memory to be unlocked before it can be used.

Q: Can I use the `FLASH_Optimize()` function to optimize the flash memory when it is locked?

A: No, you cannot use the FLASH_Optimize() function to optimize the flash memory when it is locked. The FLASH_Optimize() function requires the flash memory to be unlocked before it can be used.