Fix serial connection reliability issues

[sensei-hacker]

User description

Summary

Fixes intermittent connection failures where the configurator would fail to connect to the flight controller with MSP timeouts or confusing "connection canceled" messages. It wouldn't reconnect until Configurator is closed and re-opened. This was due to leaking the file descriptor.

Changes

1. Fix error handler in serial.js

The error handler was resolving with {error: false} when there was an actual error. This caused:

• Confusing "connection opened but request was canceled" messages
• Improper error propagation preventing retry logic from working correctly

Before: resolve({error: false, id: this._id++});
After: resolve({error: true, msg: error.message || 'Serial port error'});

2. Reset MSP decoder state before adding receive listeners

Moved FC.resetState() earlier in the connection sequence and added MSP.disconnect_cleanup() to reset the MSP decoder state. This ensures:

• Garbage bytes received during USB enumeration don't corrupt the decoder
• Boot messages from the FC don't leave the decoder in an invalid state
• Clean decoder state (IDLE) before any data is processed

Testing

• Verified connection works after fresh restart
• Tested 3 disconnect/reconnect cycles - all successful
• Confirmed MSP decoder starts in state 0 (IDLE) for all received data

Related Issues

Fixes regression introduced in PR #2476 (error handler bug)

---

PR Type

Bug fix

---

Description

• Fix error handler incorrectly reporting success on serial port errors

• Reset MSP decoder state before adding receive listeners to prevent corruption

• Ensure clean decoder state (IDLE) before processing any received data

• Add logging for serial port errors to aid debugging

---

Diagram Walkthrough

flowchart LR
  A["Serial Port Error"] -->|Before: resolve error:false| B["Confusing Messages"]
  A -->|After: resolve error:true| C["Proper Error Handling"]
  D["USB Enumeration"] -->|Garbage Bytes| E["Corrupted MSP Decoder"]
  D -->|Reset State First| F["Clean Decoder State"]
  C --> G["Successful Reconnection"]
  F --> G

Loading

File Walkthrough

Relevant files

Bug fix

serial.js Fix serial error handler to report errors correctly            js/main/serial.js Fixed error handler to correctly report error: true instead of error: false when serial port errors occur Added console logging for serial port errors to improve debugging Corrected error message propagation to include error details +4/-2      serial_backend.js Reset MSP decoder state before listeners added                      js/serial_backend.js Moved FC.resetState() and added MSP.disconnect_cleanup() earlier in connection sequence Reset MSP decoder state before adding receive listeners to prevent garbage bytes from corrupting decoder Ensures decoder starts in IDLE state before processing any received data +5/-2

---

[qodo-code-review]

You are nearing your monthly Qodo Merge usage quota. For more information, please visit here.

PR Compliance Guide 🔍

All compliance sections have been disabled in the configurations.