This fork of the Zephyr HCI UART example adds a custom HCI Command to allow for timesync between the Bluetooth Host and the Bluetooth Controller. When the HCI LE Read ISO Clock command is received, the Controller toggles a GPIO and returns its current Bluetooth LE ISO Clock in the Command Complete Event.

It has been tested on the nRF5340 Audio DK, but it should work with any nRF5340 dev kit.

Requirements

nRF Connect SDK v2.8 or newer

HCI LE Read ISO Clock Command

OGF: 0x3f, OCF: 0x200
Parameters: Flags (1 Octet) unused
Response: HCI Command Complete Event with status and 4 bytes timestamp in microseconds

nRF5340 Development Kit

The first Virtual UART (UART1, ...) is Zephyr UART 1 The second Virtual UART (UART2, ...) is Zephyr UART 0

Pinout

Signal direction as seen from the nRF5340.

PIN	Arduino	MCU	Direction
TX	D0	P1.00	out
RX	D1	P1.01	in
RTS	D7	P1.11	out
CTS	D8	P1.10	in
Time Sync	D10	P1.06	out

HCI over USB CDC

west build --pristine -b nrf5340dk/nrf5340/cpuapp -- -DEXTRA_DTC_OVERLAY_FILE=usb.overlay -DOVERLAY_CONFIG=overlay-usb.conf

HCI over UART 0 connected to second Virtual UART in J-Link Probe

west build --pristine -b nrf5340dk/nrf5340/cpuapp

HCI over second Virtual port / UART 0
Boot banner on Arduino Header UART (P1.01) / UART 1

HCI over UART 1 connected to first Virtual UART in J-Link Probe as well as Arduino Headers

west build --pristine -b nrf5340dk/nrf5340/cpuapp -- -DEXTRA_DTC_OVERLAY_FILE=uart1.overlay

No Boot Banner on Arduino Header UART

nRF5340 Audio DK

The first UART (UART1, P1.04, P1.05) is only available via test points (TP60, TP61, ...) The second UART (UART2, P1.08, P1.09) is connected to the Arduino headers.

Pinout

Signal direction as seen from the nRF5340.

PIN	Arduino	MCU	Direction
TX	D0	P1.09	out
RX	D1	P1.08	in
RTS	D7	P1.11	out
CTS	D8	P1.10	in
Time Sync	D10	P1.01	out

HCI over USB CDC

west build --pristine -b nrf5340_audio_dk/nrf5340/cpuapp -- -DEXTRA_DTC_OVERLAY_FILE=usb.overlay -DOVERLAY_CONFIG=overlay-usb.conf

HCI over UART 0 connected to Virtual UART in J-Link Probe

west build --pristine -b nrf5340_audio_dk/nrf5340/cpuapp

HCI over UART 1 connected to Virtual UART in J-Link Probe as well as Arduino Headers

Release build:

west build --pristine -b nrf5340_audio_dk/nrf5340/cpuapp -- -DEXTRA_DTC_OVERLAY_FILE=uart1.overlay

Debug build:

west build --pristine -b nrf5340_audio_dk/nrf5340/cpuapp -- -DEXTRA_DTC_OVERLAY_FILE=uart1.overlay -DOVERLAY_CONFIG=debug.conf

To use UART 1 via Arduino headers, the virtual UART of the J-Link probe needs to be disabled, e.g. with the JLink Configuration Tool.