Summary

The DEXP (Downward Expander / noise gate) toggle and level slider in the PHONE applet are non-functional on firmware v1.4.0.0. The UI is present but the radio rejects all attempted commands with error 0x5000002D (unknown parameter).

Commands tested

All return R<seq>|5000002D|:

• transmit set dexp=0
• transmit set noise_gate_level=50
• transmit set noise_gate_enabled=0
• transmit set noise_gate=0

FlexLib reference

• noise_gate_level parsing is commented out in FlexLib Radio.cs (line 9810)
• No dexp key or command exists anywhere in FlexLib
• The DEXP button appears in the SmartSDR Windows UI, suggesting it may be implemented at a higher protocol level or added in newer firmware

Investigation needed

• Check if DEXP is supported on newer firmware versions (v2.x, v3.x)
• Capture Wireshark traffic from SmartSDR Windows client when toggling DEXP to identify the actual protocol command
• May need to check if it's a slice-level command rather than a transmit-level command

Current state

• DEXP row (button + slider) is present in PhoneApplet UI
• TransmitModel has setDexp() and setDexpLevel() methods
• Status parsing for dexp and noise_gate_level keys is in applyTransmitStatus()
• Everything is wired up and ready — just needs the correct command format

Files

• src/gui/PhoneApplet.cpp — DEXP UI row
• src/models/TransmitModel.h / .cpp — DEXP state, commands, parsing