"External Mode Open Protocol CheckData command failed" Error
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I am trying to implement a PI controller with an STM32F401RE Nucleo board. I am tryping to run the model in external mode but I get this error:
External Mode Open Protocol CheckData command failed
Caused by:
- Multiple errors detected.
- XCP internal error: timeout expired, in response to XCP SYNCH command
- Error detected while trying to disconnect Simulink from target application.
- XCP error: XCP internal error: No server connected
The model compiles without any error, builds and connects with the board. This error comes up only when it is tryping to run on the target. The time stamp reads 0.00 for a few seconds and then this error pops up.

4 Comments
Masoud Vaezi
on 26 Feb 2023
Hi
I wonder if you could solve this problem. I am getting the same error.
Ege Gediksiz
on 7 Apr 2023
Same problem with Nucleo- STM32G431KB. I can deploy the model on the board, but for "Monitor & Tune" I get the same XCP error. It is weird cause I don't think these boards use XCP protocol.
I have enabled all the necessary DMA and USART settings for external mode but this happens. Hope the staff answers this problem soon.
ROBbb
on 27 Jul 2023
I have the same problem... please help us!!
Luuk Paul
on 8 Sep 2023
try going to hardware settings/target hardware resources/external mode and switch the communication interface to tcp/ip. worked for me
Answers (2)
Narvik
on 27 Oct 2023
1 vote
Hi Samuel Osei Fobi,
I understand that you are facing an issue while trying to run your PI controller model in external mode. The error “External Mode Open Protocol CheckData command failed” might occur when the connection to STM32F401RE Nucleo board is blocked.
It is possible that certain firewall settings on your system are blocking the connection, causing the external mode to stop or crash immediately upon starting. To resolve this issue, please review your firewall settings and ensure that they allow the necessary connections for the external mode to operate properly.
Hope this helps!
2 Comments
Hassan
on 11 Apr 2024
can you explain it more?
AJAY KUMAR SATALAGAON
on 30 Jan 2025
Thanks for your answer. I switched off firewall and network setting in the PC and then tried to run the Moniter and tune mode with F28379D micro-controller. The error dispapperared.
René
on 18 Sep 2024
0 votes
Hola, lo que me funciono fue cambiar "fundamental sample time" in solver, regresarlo a "Auto"
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