Zephyr BLE Throughput

This project aims to maximize the data throughput of a Bluetooth LE 5 Peripheral to a Bluetooth Dongle connected to a Linux host using two Nordic nRF52840 Dongles.

The Firmware of the Bluetooth LE 5 Peripheral and the Dongle are built with the Zephyr RTOS.

The instructions in this README require a Linux System that has BlueZ version 5.51 or newer running.

Zephyr BLE Peripheral

Bluetooth LE 5 Peripheral Firmware for the Nordic nRF52840 Dongle using the Zephyr RTOS.

The Peripheral hosts a GATT service (UUID: abcdef00-f5bf-58d5-9d17-172177d1316a) that contains the following GATT characteristics:

Configuration (UUID: abcdef01-f5bf-58d5-9d17-172177d1316a, R/W):

• interval_ms (uint16_t): The interval in milliseconds at which notifications are sent on the Data characteristic.
• data_length (uint8_t): The size in bytes of each notification.

Data (UUID: abcdef02-f5bf-58d5-9d17-172177d1316a, R/N): The notifications of this characteristic are used to transfer the data. For simple verification, each notification data is just a byte array with incrementing values: [0x00, 0x01, ... data_length-1].
When notifications are enabled, a Kernel Timer is started with the timeout and interval parameters set to interval_ms.

Setup for Eclipse

Create Eclipse Project

$ source zephyr/zephyr-env.sh
$ cd zephyr-ble-peripheral
$ cmake -G"Eclipse CDT4 - Ninja" -DBOARD=nrf52840dongle_nrf52840 -B ../zephyr-ble-peripheral-cdt -S .

Import the Project in Eclipse from the zephyr-ble-peripheral-cdt directory.

Configure the Zephyr Kernel

Build the guiconfig target from the Build Target of the project.

Build the Application

Build the all target from the Build Target of the project.

The binary will be stored in zephyr-ble-peripheral-cdt/zephyr/zephyr.hex.

Flash the Application

$ cd zephyr-ble-peripheral-cdt
# Package the application for the bootloader:
$ nrfutil pkg generate --hw-version 52 --sd-req=0x00 --application zephyr/zephyr.hex --application-version 1 peripheral.zip
# Flash it onto the board
$ nrfutil dfu usb-serial -pkg peripheral.zip -p /dev/ttyACM0

(Optional) Connect to Zephyr Console

The firmware has the USB console enabled (based of samples/subsys/usb/console) for kernel and application logs. The bluetooth stack is configured to log debug messages.

When running the peripheral, the USB console can be accessed with a serial port program, e.g.:

$ minicom -D /dev/ttyACM0

Zephyr BLE Dongle

The hci_usb folder is a copy of the zephyr/samples/bluetooth/hci_usb sample with some adjustments to the prj.conf file.

Build the Application

$ source zephyr/zephyr-env.sh
$ cd zephyr-ble-peripheral/hci_usb
$ mkdir build
$ cd build
$ cmake -G"Ninja" -DBOARD=nrf52840dongle_nrf52840 ..
$ ninja

The binary will be stored in zephyr-ble-peripheral/hci_usb/build/zephyr/zephyr.hex.

Flash the Application

$ cd zephyr-ble-peripheral/hci_usb/build
# Package the application for the bootloader:
$ nrfutil pkg generate --hw-version 52 --sd-req=0x00 --application zephyr/zephyr.hex --application-version 1 dongle.zip
# Flash it onto the board
$ nrfutil dfu usb-serial -pkg dongle.zip -p /dev/ttyACM0

Enable 2MBit PHY support in BlueZ

Since BlueZ version 5.51 support for the 2MBit PHY can be enabled with the btmgmt tool:

$ sudo btmgmt phy LE1MTX LE1MRX LE2MTX LE2MRX

BLE Throughput Test

The scripts folder contains the Python script for the throughput test:

$ cd zephyr-ble-peripheral/scripts
$ ./throughput_test.py

Before running the script make sure that 2MBit PHY support is enabled in BlueZ.

The script

1. discovers a peripheral that advertises the Throughput GATT service
2. connects to it
3. writes the given interval_ms and data_length parameters to the Configuration characteristic
4. enables notifications on the Data characteristic
5. receives a given number of notifications
6. disables notifications on the Data characteristic again

For notification reception, the script uses the AcquireNotify method of the BlueZ GATT DBus API to avoid the usage of DBus signals.