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Unable to set default PHY stm32wb55rg


We're using the stm32wb55rg as the core MCU in a project requiring decently high-frequency BLE notifications to a mobile device (100Hz update rate on the characteristic). In testing this I found that, with default settings, the bluetooth connection was unstable and frequently dropped with a Connection Timeout error from CPU2. This seemed to be alleviated when I reduced the publishing frequency, however publishing at 100Hz is a requirement of the project. Given this, I researched and found a way to configure the 2M PHY as the default for transmissions, and wrote code to attempt to configure this (TlWrite with opcode = 0x0031, and a payload specifying the 2M PHY for transmissions). The response from CPU2 indicates that it does not recognize this opcode, despite the fact that the firmware I flashed onto it should support it according to the docs (I'm using the latest version of the BLE full stack coproc firmware)

Why is CPU2 not recognizing the SetDefaultPHY command? And what modifications should I make to resolve this?
Please note that my project is not using stm32cube.

ST Employee


The opcode for HCI_LE_SET_DEFAULT_PHY command is 0x2031, so if you send a command opcode = 0x0031 that's why the CPU2 CPU2 indicates that it does not recognize the opcode.

Best Regards