Cypress Bluetooth over UART Transport Driver for Windows

This project implements a Bluetooth HCI over UART transport (H4) driver for various Cypress/Broadcom Wi-Fi + BT combo chips.

Supported hardware

The initialization sequence is virtually the same on all these combo chips, so as long as the proper firmware is provided, the driver should bring-up the device in a fully operational state.

We currently provide firmware/support for the following chips:

• CYW43455 (BCM4345C0.hcd) - extensively tested on a Raspberry Pi 4
• CYW43438 (BCM43430A1.hcd) - tested on a Raspberry Pi 3 model B at a baud rate of 460800 (but unreliable as the RTS/CTS lines are not exposed)

Note: since this driver uses the H4 protocol for communication, the UART link must support hardware flow control to prevent packet loss.

Driver configuration

The registry settings can be found under HKLM\System\CurrentControlSet\Services\cywbtserialbus\Parameters:

• BaudRate [default=460800] - the UART baud rate for communication between the host and the BT device after firmware download

• SkipFwDownload [default=0] - use the existing ROM firmware (with limited functionality)

Credits

This driver is based on the serialhcibus sample provided by Microsoft.

The firmware files come from: https://github.com/RPi-Distro/bluez-firmware/tree/master/broadcom