STM32G431 + Simulink External Mode: DWARF Parser error + Connected IO "IO server is not flashed properly" — both fail after successful Build/Deploy

Setup:

• Board: Custom PCB with STM32G431CBT6 (LQFP48)
• MATLAB/Simulink R2026a, STM32 Microcontroller Blockset (CubeMX-integrated workflow)
• Model reads an SPI absolute encoder (AS5047D) via SPI1, using two chained SPI Controller Transfer blocks (Chip select: "Provided by the SPI peripheral"), then computes angle/speed via Unwrap → Discrete Derivative → Discrete Filter, output to two Outport blocks (angle_count, w).

What works:

• Build, Deploy & Start completes successfully every time, no build errors.
• A separate hand-written CubeIDE blink test confirms the board, ST-Link, and SWD connection are all healthy.

Problem — Monitor & Tune / Connect fails, but with two different errors depending on the attempt (not simultaneously — one or the other):

On some attempts, I get:

External Mode Open Protocol Connect command failed Caused by: DWARF Parser internal error: Parser::describeSymbol xcpDummyDoubleVariable is not a global variable

On other attempts (after power-cycling the board / rebuilding), I instead get these two together:

Error: External Mode Open Protocol Connect command failed Caused by: Could not connect to target application: XCP internal error: timeout expired, in response to XCP CONNECT command Error: Unable to connect to the 'STM32G4xx Based' target for 'BLDC_HIL'.

Both occur on the same model, same board, same COM port — I haven't found a consistent trigger for which one shows up on a given attempt. This inconsistency itself feels like a clue, but I haven't been able to pin down what's different between attempts that produces one error vs. the other.

Things I've already checked/ruled out:

• Signal logging is enabled on both Outport signals
• Outport blocks are real Simulink Outports (not To Workspace — this was an earlier mistake I already fixed)
• USART3 is enabled (Asynchronous mode) with DMA added for USART3_RX, per the CubeMX prompt
• COM port in Model Settings matches Device Manager's actual assigned port (COM9)
• No other application (CubeIDE, terminal) is holding the COM port during connect
• Checked xcp_ext_common.c — the xcpDummyDoubleVariable dead-code-elimination workaround already exists in my MATLAB install, so that's not the cause

Problem 2 — Connected IO (tried as an alternative) fails with:

MATLAB System block 'BLDC_HIL/SPI Controller Transfer' error occurred when invoking 'setupImpl' method of 'stm32cube.blocks.SPIControllerTransfer'. Caused by: Simulink Connected IO: Error: IO server is not flashed properly. Reconnect the board and try again.

Question: Given the board itself is confirmed healthy (blink test via CubeIDE works fine), what else commonly causes External Mode/XCP and Connected IO to fail specifically on STM32G4-family boards? Is there a known compatibility issue between the STM32 Microcontroller Blockset's XCP-over-UART implementation and G4-series parts specifically?

Answer 1

[Vikky Patil]

Try to follow the steps mentioned here :

https://in.mathworks.com/matlabcentral/answers/2184289-xcp-internal-error-timeout-expired-in-response-to-xcp-connect-command-external-mode-open-protoco?s_tid=srchtitle

Regards,

Vikky