Use HCI access to NimBLE controller

This tutorial explains how to use the example application blehci included in the NimBLE stack to talk to the Mynewt NimBLE controller via the Host Controller Interface. You may build the Mynewt image using a laptop running any OS of your choice - Mac, Linux, or Windows.

The host used in this specific example is the BlueZ Bluetooth stack. Since BlueZ is a Bluetooth stack for Linux kernel-based family of operating system, the tutorial expects a computer running Linux OS and with BlueZ installed to talk to the board with the Mynewt image.


Ensure that you meet the following prerequisites before continuing with one of the tutorials.

  • Have Internet connectivity to fetch remote Mynewt components.

  • Have a board with BLE radio that is supported by Mynewt. We will use an nRF52 Dev board in this tutorial.

  • Have a USB TTL Serial Cable that supports hardware flow control such as ones found at to establish a serial USB connection between the board and the laptop.

  • Install the newt tool and toolchains (See Basic Setup).

  • Install a BLE host such as BlueZ on a Linux machine to talk to the nRF52 board running Mynewt. Use sudo apt-get install bluez to install it on your Linux machine.

Create a project

Use the newt tool to create a new project directory containing a skeletal Mynewt framework. Change into the newly created directory.

$ newt new blehciproj
Downloading project skeleton from apache/mynewt-blinky...
Installing skeleton in blehciproj ...
Project blehciproj  successfully created.
$ cd mblehciproj

$ newt upgrade
Downloading repository mynewt-core (commit: master) ...
apache-mynewt-core successfully upgraded to version 1.7.0

Create targets

You will create two targets - one for the bootloader, the other for the application. Then you will add the definitions for them. Note that you are using the example app blehci for the application target. Set the bsp to nordic_pca10040.

NOTE: The preview version, nRF52PDK, is no longer supported. If you do not see PCA100040 on the top of your board, you have a preview version of the board and will need to upgrade your developer board before continuing.

$ newt target create nrf52_boot
$ newt target set nrf52_boot app=@mcuboot/boot/mynewt
$ newt target set nrf52_boot bsp=@apache-mynewt-core/hw/bsp/nordic_pca10040
$ newt target set nrf52_boot build_profile=optimized
$ newt target create myble2
$ newt target set myble2 bsp=@apache-mynewt-core/hw/bsp/nordic_pca10040
$ newt target set myble2 app=@apache-mynewt-nimble/apps/blehci
$ newt target set myble2 build_profile=optimized

Check that the targets are defined correctly.

$ newt target show

Build targets

Then build the two targets.

$ newt build nrf52_boot
Linking ~/dev/blehciproj/bin/targets/nrf52_boot/app/boot/mynewt/mynewt.elf
Target successfully built: targets/nrf52_boot

$ newt build myble2
Linking ~/dev/blehciproj/bin/targets/myble2/app/apps/blehci/blehci.elf
Target successfully built: targets/myble2

Create the app image

Generate a signed application image for the myble2 target. The version number is arbitrary.

$ newt create-image myble2 1.0.0
App image succesfully generated: ~/dev/blehciproj/bin/targets/myble2/app/apps/blehci/blehci.img

Load the bootloader and the application image

Make sure the USB connector is in place and the power LED on the board is lit. Use the Power ON/OFF switch to reset the board after loading the image.

Load the bootloader:

$ newt load nrf52_boot
Loading bootloader

Load the application image:

$ newt load myble2
Loading app image into slot 1

Establish serial connection

Attach a serial port to your board by connecting the USB TTL Serial Cable. This should create /dev/ttyUSB0 (or similar) on your machine.

Note Certain Linux OS versions have been observed to detect the nrf52 board as a mass storage device and the console access doesn’t work properly. In that case try powering the nrf52 board from your monitor or something other than your Linux computer/laptop when you set up the serial port for HCI communication.

Open Bluetooth monitor btmon

btmon is a BlueZ test tool to display all HCI commands and events in a human readable format. Start the btmon tool in a terminal window.

$ sudo btmon
[sudo] password for admin:
Bluetooth monitor ver 5.37

Attach the blehci device to BlueZ

In a different terminal, attach the blehci device to the BlueZ daemon (substitute the correct /dev filename for ttyUSB0).

$ sudo btattach -B /dev/ttyUSB0 -S 1000000
Attaching BR/EDR controller to /dev/ttyUSB0
Switched line discipline from 0 to 15
Device index 1 attached

The baud rate used to connect to the controller may be changed by overriding the default value of 1000000 in the net/nimble/transport/uart/syscfg.yml. Settings in the serial transport syscfg.yml file can be overridden by a higher priority package such as the application. So, for example, you may set the BLE_HCI_UART_BAUD to a different value in apps/blehci/syscfg.yml.

If there is no CTS/RTS lines present in the test environment, flow control should be turned off. This can be done with -N option for btattach. Note: -N option came with BlueZ ver 5.44. Also, modify the value of BLE_HCI_UART_FLOW_CTRL in the nimble/transport/uart/syscfg.yml to HAL_UART_FLOW_CTL_NONE.

Start btmgmt to send commands

In a third terminal, start btmgmt. This tool allows you to send commands to the blehci controller. Use the index number that shows up when you btattach in the previous step.

$ sudo btmgmt --index 1
[sudo] password for admin:

Set your device address (you can substitute any static random address here).

[hci1]# static-addr cc:11:11:11:11:11
Static address successfully set

Initialize the controller.

[hci1]# power on
hci1 Set Powered complete, settings: powered le static-addr

Begin scanning.

[hci1]# find -l
Discovery started
hci1 type 6 discovering on
hci1 dev_found: 58:EF:77:C8:8D:17 type LE Random rssi -78 flags 0x0000
AD flags 0x06
eir_len 23