# BTstack Port for Zephyr RTOS

## Overview

This port targets any platform supported by Zephyr that either contains a built-in Bluetooth Controller
or is connected to an external Controller via one of the supported Zephyr HCI Transports drivers (see `zephyr/drivers/bluetooth/hci`)

## Status

Tested with nRF52 DK (PCA10040), nRF52840 DK (PC10056) and nRF5340 DK (PCA10095) boards only. It uses the fixed static random BD ADDR stored in NRF_FICR/NRF_FICR_S, which will not compile on non nRF SoCs.

## Build Environment
The first step needs to done once. Step two is needed every time to setup the environment.

### 1. Build Environment Preconditions

Follow the getting started [guide](https://docs.zephyrproject.org/latest/develop/getting_started/index.html)
until you are able to build an example.

Then update the `ZEPHYR_ROOT` variable in `env.sh` to point to your `zephyrproject`. Defaults to `~/zephyrproject`


### 2. Prepare the build environment

To setup your environment to build a BTstack example, run the provided setup in `env.sh`.

```sh
source env.sh
```

## Building and Running on nRF52840

### 1. Build Example

You can build an example using:
```sh
west build -b nrf52840dk_nrf52840
```

`nrf52840dk_nrf52840` selected the Nordic nRF52840 DK. For the older nRF52 DK with nRF52832, you can specify nrf52dk_nrf52832.
To get a list of all supported Zephyr targets, run `west boards`

To change zephyr platform settings use:
```sh
west build -b nrf52840dk_nrf52840 -t menuconfig
```

To build a different example, e.g. the `gatt_streamer_server`, set the EXAMPLE environment variable:
```sh
EXAMPLE=gatt_streamer_server west build -b nrf52840dk_nrf52840
```

### 2. Flash Example

To flash a connected board:
```sh
west flash
```

## Buiding and Running on nRF5340

The nrf5340 is a dual core SoC, where one core is used for Bluetooth HCI functionality and
the other for the high level application logic. So both cores need to be programmed separately.
Using the nRF5340-DK for example allows debug output on both cores to separate UART ports.
For the nRF5340 a network core firmware is required, which one depends on the use-case.
With 2a and 2b two options are given.

### 1. Building the application
build using:
```sh
west build -b nrf5340dk_nrf5340_cpuapp
```
with debug:
```sh
west build -b nrf5340dk_nrf5340_cpuapp -- -DOVERLAY_CONFIG=debug_overlay.conf
```

### 2a. Using zephyr network core image
the `hci_rgmsg` application needs to be loaded first to the network core.
Configure network core by selecting the appropriate config file, for example `nrf5340_cpunet_iso-bt_ll_sw_split.conf`.
additionally it's required to increase the main stack size from
```sh
CONFIG_MAIN_STACK_SIZE=512
```
to
```sh
CONFIG_MAIN_STACK_SIZE=4096
```
then the network core image can be compiled and flashed
```sh
west build -b nrf5340dk_nrf5340_cpunet -- -DCONF_FILE=nrf5340_cpunet_iso-bt_ll_sw_split.conf
west flash
```
or with debugging
```sh
west build -b nrf5340dk_nrf5340_cpunet -- -DCONF_FILE=nrf5340_cpunet_iso-bt_ll_sw_split.conf -DOVERLAY_CONFIG=debug_overlay.conf
west flash
```

### 2b. Using Packetcraft binary network core image
for nrf5340 the latest netcore firmware is located at [sdk-nrf](https://github.com/nrfconnect/sdk-nrf/tree/main/lib/bin/bt_ll_acs_nrf53/bin)
to program it:
```sh
nrfjprog --program ble5-ctr-rpmsg_<version number>.hex --chiperase --coprocessor CP_NETWORK -r
```

## TODO

- Allow/document use of Zephyr HCI Drivers