Bluetooth firmware for the Arduino 101

The Arduino 101 board comes with a Nordic Semiconductor nRF51 Bluetooth LE controller. The Arduino 101 factory-installed firmware on this controller is not supported by Zephyr, so a new one needs to be flashed onto it. The best option currently is to use MyNewt (http://mynewt.apache.org) as a basis for this firmware, which makes it possible to use the controller with the native Bluetooth stack of Zephyr.

Building the firmware yourself

Set up the newt tool. For Fedora the dependencies are:

$ sudo dnf install dfu-util libcurl-devel golang arm-none-eabi-gdb \
          arm-none-eabi-newlib arm-none-eabi-gcc-cs \
          arm-none-eabi-binutils-cs arm-none-eabi-gcc-cs-c++

General instructions, as well as Ubuntu/Debian dependencies can be found here: http://mynewt.apache.org/newt/install/newt_linux/

Once the newt tool is installed create your project:

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

Currently the necessary code is only available in the ‘develop’ branch of MyNewt, aliased by version number ‘0.0.0’. To use this, edit project.yml and change “vers: 0-latest” to “vers: 0-dev”. After that, initialize the project with:

$ newt install -v
apache-mynewt-core
Downloading repository description for apache-mynewt-core... success!
Downloading repository incubator-mynewt-core (branch: master; commit: develop) at https://github.com/apache/incubator-mynewt-core.git
Cloning into '/tmp/newt-repo604330290'...
remote: Counting objects: 21889, done.
remote: Compressing objects: 100% (97/97), done.
remote: Total 21889 (delta 49), reused 0 (delta 0), pack-reused 21784
Receiving objects: 100% (21889/21889), 7.63 MiB | 1.13 MiB/s, done.
Resolving deltas: 100% (12945/12945), done.
Checking connectivity... done.
apache-mynewt-core successfully installed version 0.0.0-none

Create a target for the bootloader:

$ newt target create boot
$ newt target set boot app=@apache-mynewt-core/apps/boot
$ newt target set boot bsp=@apache-mynewt-core/hw/bsp/nrf51-arduino_101
$ newt target set boot build_profile=optimized

Create a target for the HCI over UART application:

$ newt target create blehci
$ newt target set blehci app=@apache-mynewt-core/apps/blehci
$ newt target set blehci bsp=@apache-mynewt-core/hw/bsp/nrf51-arduino_101
$ newt target set blehci build_profile=optimized

Verify that the targets were properly created:

$ newt target show
targets/blehci
    app=@apache-mynewt-core/apps/blehci
    bsp=@apache-mynewt-core/hw/bsp/nrf51-arduino_101
    build_profile=optimized
targets/boot
    app=@apache-mynewt-core/apps/boot
    bsp=@apache-mynewt-core/hw/bsp/nrf51-arduino_101
    build_profile=optimized

Build the bootloader

$ newt build boot
Compiling...
...
Linking boot.elf
App successfully built: <path>/arduino-mynewt/bin/boot/apps/boot/boot.elf

Build the HCI over UART application:

$ newt build blehci
Compiling...
...
Linking blehci.elf
App successfully built: <path>/arduino-mynewt/bin/blehci/apps/blehci/blehci.elf

$ newt create-image blehci 0.0.0
App image succesfully generated: <path>/arduino-mynewt/bin/blehci/apps/blehci/blehci.img
Build manifest: <path>/arduino-mynewt/bin/blehci/apps/blehci/manifest.json

Combine the bootloader and application into a single firmware image (ble_core.img)

$ cat bin/boot/apps/boot/boot.elf.bin /dev/zero | dd of=ble_core.img bs=1k count=256
$ dd if=bin/blehci/apps/blehci/blehci.img of=ble_core.img bs=1 seek=32768

Reset Arduino 101 with USB plugged and wait a few seconds (you might need several repeated attempts):

$ dfu-util -a ble_core -D ble_core.img
...
Opening DFU capable USB device...
ID 8087:0aba
Run-time device DFU version 0011
Claiming USB DFU Interface...
Setting Alternate Setting #8 ...
Determining device status: state = dfuIDLE, status = 0
dfuIDLE, continuing
DFU mode device DFU version 0011
Device returned transfer size 2048
Copying data from PC to DFU device
Download  [=========================] 100%        69008 bytes
Download done.
state(2) = dfuIDLE, status(0) = No error condition is present
Done!

After successfully completing these steps your Arduino 101 should now have a HCI compatible BLE firmware. The Zephyr tree contains several sample config files for this firmware (named after the MyNewt BLE stack, Nimble), e.g. samples/bluetooth/peripheral_hr/prj_nimble.conf

Getting HCI traces

By default you will only see normal log messages on the console, without any way of accessing the HCI traffic between Zephyr and the nRF51 controller. There is however a special Bluetooth logging mode that converts the console to use a binary protocol that interleaves both normal log messages as well as the HCI traffic. To enable this protocol the following Kconfig options need to be set:

CONFIG_BLUETOOTH_DEBUG_MONITOR=y
CONFIG_UART_CONSOLE=n
CONFIG_UART_QMSI_1_BAUDRATE=1000000

The first item replaces the BLUETOOTH_DEBUG_STDOUT option, the second one disables the default printk/printf hooks, and the third one matches the console baudrate with what’s used to communicate with the nRF51, in order not to create a bottle neck.

To decode the binary protocol that will now be sent to the console UART you need to use the btmon tool from BlueZ 5.40 or later:

$ btmon --tty <console TTY> --tty-speed 1000000