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Linux Setup

The following steps are required to use the CYW20735B1 evaluation kit as normal HCI device on Linux with BlueZ.

1. Setup as HCI device

You need to set the baud rate to 3 Mbit/s. Replace /dev/ttyUSB0 with your device.

btattach -B /dev/ttyUSB0 -S 3000000

If this does not work directly, use:

stty -F /dev/ttyUSB0 3000000
btattach -B /dev/ttyUSB0

Sometimes, you need to plug/unplug the evaluation board multiple times and run a combination of the commands above. If setup was successful can be checked with hciconfig. A MAC address with all zeros indicates that the baud rate was not set correctly and you need to try again.

2. Use with BlueZ

Assuming that you already have a regular Bluetooth device, you new device is hci1.

hciconfig hci1 up

You can list your HCI devices:

hcitool dev

3. Command line tools for connections

Scanning for devices:

hcitool scan
hcitool lescan

Connections and pairing:


Enter into bluetoothctl command prompt:

power on
agent on
scan on

Optional - accept connections:

advertise on
pairable on
discoverable on

Do a pairing and then connect:

pair aa:bb:cc:dd:ee:ff
connect aa:bb:cc:dd:ee:ff


On some devices, diagnostic logging for LMP and LCP already works out of the box. Note that diagnostics can do more, but the additional features are currently not integrated into BlueZ or the Linux kernel.

To enable diagnostics, execute:

echo 1 > /sys/kernel/debug/bluetooth/hci0/vendor_diag

By default, this entry is only created for Intel and Broadcom chips. The evaluation board claims to be Cypress, a different vendor ID, thus the vendor diagnostics are missing. BlueZ already comes with a monitor that decodes some parts of the diagnostic traffic, simply run:

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