General • How to I solve this error

I am an older guy new to the Raspberry Pi Pico H.

I have programmed a Pico H to run a model railway track (change points and stop train in a station) All went well but have recently started to get the following error:

PROBLEM IN THONNY'S BACK-END: Exception while handling 'Run' (ConnectionError: EOF).
See Thonny's backend.log for more info.
You may need to press "Stop/Restart" or hard-reset your MicroPython device and try again.
Process ended with exit code 1.
Unable to connect to COM3: port not found
Process ended with exit code 1.

I cannot understand the backend.log which reads:

14:07:44.744 [MainThread] INFO thonny: Thonny version: 4.1.4
14:07:44.744 [MainThread] INFO thonny: cwd: C:\Users\brian
14:07:44.744 [MainThread] INFO thonny: original argv: ['C:\\Users\\brian\\AppData\\Local\\Programs\\Thonny\\python.exe', '-s', '-u', '-B', 'C:\\Users\\brian\\AppData\\Local\\Programs\\Thonny\\lib\\site-packages\\thonny\\plugins\\rp2040\\rp2040_back.py', "{'clean': True, 'port': 'COM3', 'dtr': None, 'rts': None, 'submit_mode': 'raw_paste', 'interrupt_on_connect': True, 'write_block_size': 64, 'write_block_delay': None, 'proxy_class': 'RaspberryPiPicoBackendProxy', 'sync_time': True, 'validate_time': False, 'local_rtc': True}"]
14:07:44.744 [MainThread] INFO thonny: sys.executable: C:\Users\brian\AppData\Local\Programs\Thonny\python.exe
14:07:44.744 [MainThread] INFO thonny: sys.argv: ['C:\\Users\\brian\\AppData\\Local\\Programs\\Thonny\\lib\\site-packages\\thonny\\plugins\\rp2040\\rp2040_back.py', "{'clean': True, 'port': 'COM3', 'dtr': None, 'rts': None, 'submit_mode': 'raw_paste', 'interrupt_on_connect': True, 'write_block_size': 64, 'write_block_delay': None, 'proxy_class': 'RaspberryPiPicoBackendProxy', 'sync_time': True, 'validate_time': False, 'local_rtc': True}"]
14:07:44.744 [MainThread] INFO thonny: sys.path: ['C:\\Users\\brian\\AppData\\Local\\Programs\\Thonny\\lib\\site-packages\\thonny\\plugins\\rp2040', 'C:\\Users\\brian\\AppData\\Local\\Programs\\Thonny\\python310.zip', 'C:\\Users\\brian\\AppData\\Local\\Programs\\Thonny\\DLLs', 'C:\\Users\\brian\\AppData\\Local\\Programs\\Thonny\\lib', 'C:\\Users\\brian\\AppData\\Local\\Programs\\Thonny', 'C:\\Users\\brian\\AppData\\Local\\Programs\\Thonny\\lib\\site-packages']
14:07:44.744 [MainThread] INFO thonny: sys.flags: sys.flags(debug=0, inspect=0, interactive=0, optimize=0, dont_write_bytecode=1, no_user_site=1, no_site=0, ignore_environment=0, verbose=0, bytes_warning=0, quiet=0, hash_randomization=1, isolated=0, dev_mode=False, utf8_mode=0, warn_default_encoding=0, int_max_str_digits=-1)
14:07:44.744 [MainThread] INFO thonny.plugins.micropython.bare_metal_backend: Starting backend, args: {'clean': True, 'port': 'COM3', 'dtr': None, 'rts': None, 'submit_mode': 'raw_paste', 'interrupt_on_connect': True, 'write_block_size': 64, 'write_block_delay': None, 'proxy_class': 'RaspberryPiPicoBackendProxy', 'sync_time': True, 'validate_time': False, 'local_rtc': True}

Can any kind person please interpret the above and give me advice on how to stop the error.

Thanks in anticipation of your help.
Regards
Wirralian

Statistics: Posted by Wirralian — Fri Jan 02, 2026 2:49 pm — Replies 3 — Views 78

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