Can I flash software to a development board that uses a slightly different MCU ?

[freeflyer]

I have developed software on the Nucleo-L433RC-P development board which uses the STM32L433RCT6P MCU (the P defines it has 2 x VDD12 pins for an external SMPS).

However, I have designed a PCB that uses the STM32L433RCT6 (no VDD12 pins) but want to continue developing the software on the development board until my PCB arrives.

To retarget the MCU, I edited the .ioc file and changed STM32L433RCTxP to STM32L433RCTx.

I flashed the software to the Nucleo-L433RC-P board, but I am getting strange and random issues.

It seemed to work to start with, but after several further flashes it stopped working with the error shown below...

I'm not sure but it seems to go to a reset handler in "startup_stm32l433rctxp.s"....

The console shows the following error...

STMicroelectronics ST-LINK GDB server. Version 7.11.0
Copyright (c) 2025, STMicroelectronics. All rights reserved.

Starting server with the following options:
        Persistent Mode            : Disabled
        Logging Level              : 1
        Listen Port Number         : 61234
        Status Refresh Delay       : 15s
        Verbose Mode               : Disabled
        SWD Debug                  : Enabled
        InitWhile                  : Enabled

Waiting for debugger connection...
Debugger connected
Waiting for debugger connection...
Debugger connected
Waiting for debugger connection...
      -------------------------------------------------------------------
                       STM32CubeProgrammer v2.20.0                  
      -------------------------------------------------------------------



Log output file:   C:\Users\JOHNLI~1\AppData\Local\Temp\STM32CubeProgrammer_a27024.log
ST-LINK SN  : 066BFF323355373043142426
ST-LINK FW  : V2J46M31
Board       : NUCLEO-L433RC-P
Voltage     : 3.27V
SWD freq    : 4000 KHz
Connect mode: Under Reset
Reset mode  : Hardware reset
Device ID   : 0x435
Revision ID : Rev Z
Device name : STM32L43xxx/STM32L44xxx
Flash size  : 256 KBytes
Device type : MCU
Device CPU  : Cortex-M4
BL Version  : 0x91



Opening and parsing file: ST-LINK_GDB_server_a27024.srec


Memory Programming ...
  File          : ST-LINK_GDB_server_a27024.srec
  Size          : 42.33 KB 
  Address       : 0x08000000


Erasing memory corresponding to segment 0:
Erasing internal memory sectors [0 21]
Download in Progress:


File download complete
Time elapsed during download operation: 00:00:01.504



Verifying...




Error: Data mismatch found at address  0x0800A860 (byte = 0x00 instead of 0x2E)


Time elapsed during verifying operation: 00:00:00.284


Error: Download verification failed


Encountered Error when opening C:\ST\STM32CubeIDE_1.18.1\STM32CubeIDE\plugins\com.st.stm32cube.ide.mcu.externaltools.cubeprogrammer.win32_2.2.200.202503041107\tools\bin\STM32_Programmer_CLI.exe
Error in STM32CubeProgrammer
Shutting down...
Exit.

When I tried again later in the day, it started working again but then it stopped after several flashes.

The difference in the pin out between the STM32L433RCT6P and STM32L433RCT6 MCU is highlighted in orange below...

STM32L433RCT6....

 STM32L433RCT6P

[Pavel A.]

Debuggers can be picky about exact MCU model. Try to convert the program to .bin and flash with CubeProgrammer.

[Tesla DeLorean]

Check any code related to LDO vs SMPS, if you're running on the P/SMPS chip check BSP_SMPS_xx() code

[freeflyer]

Thanks both, but something is not right.

I created a clean, new project for the Nucleo-L433RC-P board but when I try to flash the software I still get the same error.

Its as if flashing with the non-SMPS software has damaged the board, but I cant see how and would be surprised if this were the case.

Why am I unable to flash software to the Nucleo-L433RC-P board, even though I am now using the correct software  (i.e. targeted for STM32L433RCT6P) designed for this board ? 

[Pavel A.]

LDO vs SMPS is very important in runtime (and you can detect different MCUs by the product ID) but when flashing with CubeProgrammer it should not be a problem. The Programmer can flash anything, even total garbage. Use "connect under reset".

[freeflyer · Accepted solution]

I’ve changed strategy and decided to design my pcb so that it uses the same MCU (STM32L433RCT6P) as the Nucleo-L433RC-P development board. This way I can continue to develop my software until the pcb arrives without the hassle of retargeting it to a different MCU. 

I do need to be able to debug my code, not just flash it. 

So changing the MCU seemed the best solution. 

Although I do occasionally get the same error, but manage to fix it if I delete the debug folder and flash again. 

Surprisingly the STM32L433RCT6P Is slightly cheaper and more commonly available than theSTM32L433RCT6