BLHeli passthrough fails with a DakeFPV 4-in-1 ESC running Bluejay 0.21.0.

Issue details BLHeli passthrough fails with a DakeFPV 4-in-1 ESC running Bluejay 0.21.0.

SERVO_BLH_TEST=1 consistently fails with: Debug log: 22/08/2026 19:34:42 : ESC: Test FAILED 22/08/2026 19:34:42 : ESC: BL_SendCMDSetAddress 0x7C00 22/08/2026 19:34:42 : ESC: Unknown interface type 0xE8B5 22/08/2026 19:34:42 : ESC: BL_ReadBuf 8 -> 9 22/08/2026 19:34:42 : ESC: BL_ConnectEx 1/4 at 1 22/08/2026 19:34:42 : ESC: Running test on channel 1

The ESC and motors operate normally. The same ESC can be detected and configured successfully through Betaflight passthrough.

ArduPilot 4.7.0 explicitly accepts several SiLabs BLHeli bootloader device IDs in AP_BLHeli.cpp, including 0xE8B1 and 0xE8B2, but not 0xE8B5. Therefore connecting and testing this device results in: ESC: Unknown interface type 0xE8B5

Betaflight instead detects SiLabs devices using a range check: (pDeviceInfo->words[0] > 0xE800) && (pDeviceInfo->words[0] < 0xF900) so 0xE8B5 in Betaflight is accepted as a SiLabs BLHeli bootloader.

This appears to be a missing SiLabs device detection case in ArduPilot rather than an ESC communication failure.

Troubleshooting performed:

• ESC powered and motors operating normally
• Bluejay 0.21.0 confirmed
• ArduPilot BLHeli passthrough/configuration fails
• SERVO_BLH_TEST=1 consistently fails at Unknown interface type 0xE8B5
• Same ESC detects and configures correctly through Betaflight passthrough

Relevant source: ArduPilot 4.7.0: https://github.com/ArduPilot/ardupilot/blob/Copter-4.7.0/libraries/AP_BLHeli/AP_BLHeli.cpp

Betaflight: https://github.com/betaflight/betaflight/blob/master/src/main/io/serial_4way.c

Version: ArduCopter 4.7.0 Stable and ESC Bluejay V0.21.0 Platform: Copter Airframe type: Quadcopter, Quad X Hardware type

• TBS Lucid H7
• DakeFPV 70A 4-in-1 ESC

Logs

No flight log is required to reproduce the issue.