Why isn’t my STM32 microcontroller programming correctly?
If your STM32 microcontroller isn't programming correctly, there are several common causes. Here's a structured checklist to help you diagnose and solve the issue:
Common Causes and Fixes
1. Power Supply Issues
-
Is the MCU receiving the correct voltage?
-
STM32 typically runs on 3.3V.
-
-
Check for stable VDD and VSS connections.
-
Ensure decoupling capacitors (e.g., 100nF close to VDD pins).
2. SWD or JTAG Connection Problems
-
Are SWDIO, SWCLK (or JTAG) properly connected?
-
Pull-up resistors may be needed on NRST or BOOT0.
-
Make sure SWD is not disabled in the Option Bytes.
-
Try reducing the programming frequency in STM32CubeProgrammer.
3. BOOT Pin Configuration
-
On reset, check BOOT0 pin:
-
BOOT0 = 0: boots from flash (normal). -
BOOT0 = 1: boots from system memory (used for DFU, USART boot).
-
If the BOOT0 pin is floating or wrong, you may not be able to program flash.
4. Debugger/Programmer Problems
-
Are you using ST-LINK, J-Link, or USB DFU?
-
Check cable quality and try a different USB port.
-
Update ST-LINK firmware using STM32CubeProgrammer.
5. Flash Protection / Option Bytes
-
Option bytes may lock flash.
-
Use STM32CubeProgrammer → connect → check "Read Out Protection (RDP)":
-
If RDP is set to level 1 or 2, you may be blocked.
-
RDP level 1: can be removed by mass erase.
-
RDP level 2: irreversible lock!
-
6. Wrong Target Selected
-
Check if your IDE (CubeIDE, Keil, etc.) is targeting the correct STM32 part number.
7. MCU in a Faulty State
-
The MCU may be stuck in a loop or low-power mode.
-
Try:
-
Holding NRST low during programming.
-
Power cycle before and after attempting programming.
-
"Connect under reset" option in CubeProgrammer.
-
Debugging Steps
-
Open STM32CubeProgrammer.
-
Select the appropriate interface (e.g., ST-LINK).
-
Enable:
-
"Hot Plug" or
-
"Connect Under Reset"
-
-
Try erasing the chip.
-
Reprogram a minimal firmware (e.g., blinking LED).
Tools and Tips
-
Use STM32CubeIDE for debugging logs.
-
If using ST-LINK, make sure the ST-LINK driver is correctly installed.
-
Check for shorts or open connections on your custom board (if not using a dev board).
-
Make sure your reset circuit is not holding the chip in reset.

评论
发表评论