STM32F4DISCOVERY issue - RDP stuck at 0xFF

[raniaa]

Hey everyone,

I'm having a weird issue with my STM32F4DISCOVERY board (MB997). It was working fine before, but now I can't program it anymore.

Board info:

• Board: STM32F4DISCOVERY

• Device: STM32F407VGT6

• ST-LINK FW: V2J46M33

• ST-LINK SN: 0671FF37324D423143244649

Symptoms:

• STM32CubeProgrammer connects OK (Device ID 0x413 confirmed)

• Flash erase fails: Error: failed to erase memory sectors [0-2]

• RDP Option Byte shows 0xFF (corrupted)

• BOR_LEV = 3 (BOR OFF)

• Writing RDP from 0xFF to 0xAA fails, always comes back as 0xFF

• VDD measured at 2.89V

What I've tried:

• Under Reset mode

• ST-LINK Utility

• STM32cubeProgrammer

• Different USB cable

• ST-LINK firmware update

Nothing works. RDP is stuck at 0xFF.

Has anyone seen this before? Any suggestions?

Thanks in advance!

[Gyessine]

Hello @raniaa 
This is kind a weird issue to have
first did you apply any
-hardware modification
-flashed some code
-modified the RDP
between when the board was working fine and stopped working?
-Also, the 2.89V is suspicious
-also, do you feel like the MCU itself gets overheated? 
can you test the voltage at MCU level and see what you get? maybe the board voltage regulator becomes faulty
which lead to some corruption when flashing the memory: (don't forget to remove the jumper before measuring)

-Also, can you try to connect it using the under-reset mode then reprogram RDP to 0xAA enable BOR and do a power cycle
BR
Gyessine

[raniaa]

Hello,

Yes, I did flash code before the issue appeared.
I did not modify the RDP manually.

The MCU is not overheating.

I measured the voltage directly on the MCU VDD pins using a multimeter, and I get around 2.93V

[mƎALLEm]

---

@raniaa wrote:

I measured the voltage directly on the MCU VDD pins using a multimeter, and I get around 2.93V

---

The idea here is to remove JP1 and measure the voltage of the power source side on that jumper. The purpose is to detect if there is a voltage drop on the voltage regulator output while powering supply the MCU.

[raniaa]

I get around 2.94V

[MM..1]

Voltage seems ok

try measure too current over removed jumper.

[raniaa]

Measured current across J1 after removing the jumper: 0 A. Same result observed on a known good board

[mƎALLEm]

---

@raniaa wrote:

Measured current across J1 after removing the jumper: 0 A. Same result observed on a known good board

---

How did you measure the current? 0A doesn't make sense.

You need to measure the current consumption on both pins on JP1 as the following:

[raniaa]

I think there is an issue with my multimeter because I'm getting a reading of 0 on both boards 

there is not another test ? 

[MM..1]

Try connect under reset and test lower speeds less as 400kb. Next variant is use DFU mode. After connect check write protection option bytes. How is last flashed software? 

PS: Basic multimeters require reconnect wires for current meas, check labels on it.