Go Bluetooth is a cross-platform package for using [Bluetooth Low Energy](https://en.wikipedia.org/wiki/Bluetooth_Low_Energy) hardware from the Go programming language.
It can also be used running "bare metal" on microcontrollers produced by [Nordic Semiconductor](https://www.nordicsemi.com/) by using [TinyGo](https://tinygo.org/).
The Go Bluetooth package can be used to create both Bluetooth Low Energy Centrals as well as to create Bluetooth Low Energy Peripherals.
## Bluetooth Low Energy Central
A typical Bluetooth Low Energy Central would be your laptop computer or mobile phone.
This example shows a central that scans for peripheral devices and then displays information about them as they are discovered:
Go Bluetooth support for Linux uses [BlueZ](http://www.bluez.org/) via the [D-Bus](https://en.wikipedia.org/wiki/D-Bus) interface thanks to the https://github.com/muka/go-bluetooth package. This should work with most distros that support BlueZ such as Ubuntu, Debian, Fedora, and Arch Linux, among others.
Linux can be used both as a BLE Central or as a BLE Peripheral.
### Installation
You need to have a fairly recent version of BlueZ, for example v5.48 is the latest released version for Ubuntu/Debian.
sudo apt update
sudo apt install bluez
Once you have done this, you can obtain the Go Bluetooth package using Git:
Go Bluetooth support for macOS uses the [CoreBluetooth](https://developer.apple.com/documentation/corebluetooth?language=objc) libraries thanks to the https://github.com/JuulLabs-OSS/cbgo package.
As a result, it should work with most versions of macOS, although it will require compiling using whatever specific version of XCode is required by your version of the operating system.
The macOS support only can only act as a BLE Central at this time, with some additional development work needed for full functionality.
### Installation
In order to compile Go Bluetooth code targeting macOS, you must do so on macOS itself. In other words, we do not currently have cross compiler support. You must also have XCode tools installed:
xcode-select --install
Once you have done this, you can obtain the Go Bluetooth package using Git:
Go Bluetooth support for Windows uses the [WinRT Bluetooth](https://docs.microsoft.com/en-us/uwp/api/windows.devices.bluetooth.bluetoothadapter?view=winrt-19041) interfaces by way of the https://github.com/tinygo-org/bluetooth/winbt package that is part of this package.
The Windows support is still experimental, and needs additional development to be useful. At this time, it can only be used to perform scanning operations as a BLE Central.
For specifics please see https://github.com/tinygo-org/bluetooth/issues/13
### Installation
Once you have done this, you can obtain the Go Bluetooth package using Git:
Go Bluetooth has bare metal support for several chips from Nordic Semiconductor that include a built-in Bluetooth Low Energy radio.
This support requires compiling your programs using [TinyGo](https://tinygo.org/).
You must also use firmware provided by Nordic Semiconductor known as the "SoftDevice". The SoftDevice is a binary blob that implements the BLE stack. There are other (open source) BLE stacks, but the SoftDevices are pretty solid and have all the qualifications you might need. Other BLE stacks might be added in the future.
The Nordic Semiconductor SoftDevice can be used both as a BLE Central or as a BLE Peripheral, depending on which chip is being used. See the "Supported Chips" section below.
You must install TinyGo to be able to compile bare metal code using Go Bluetooth. Follow the instructions for your operating system at https://tinygo.org/getting-started/
The line of "Bluefruit" boards created by Adafruit already have the SoftDevice firmware pre-loaded. This means you can use TinyGo and the Go Bluetooth package without any additional steps required. Supported Adafruit boards include:
After you have installed TinyGo and the Go Bluetooth package, you should be able to compile/run code for your device.
For example, this command can be used to compile and flash an Adafruit Circuit Playground Bluefruit board with the example we provide that turns it into a BLE server to control the built-in NeoPixel LEDs:
The following Nordic Semiconductor chips are currently supported:
* [nRF51822](https://www.nordicsemi.com/Products/Low-power-short-range-wireless/nRF51822) with the [S110](https://www.nordicsemi.com/Software-and-Tools/Software/S110) SoftDevice (version 8). This SoftDevice does not support all features (e.g. scanning).
* [nRF52832](https://www.nordicsemi.com/Products/Low-power-short-range-wireless/nRF52832) with the [S132](https://www.nordicsemi.com/Software-and-Tools/Software/S132) SoftDevice (version 6).
* [nRF52840](https://www.nordicsemi.com/Products/Low-power-short-range-wireless/nRF52840) with the [S140](https://www.nordicsemi.com/Software-and-Tools/Software/S140) SoftDevice (version 6 and 7).
### Flashing the SoftDevice on Other Boards
To use a board that uses one of the above supported chips from Nordic Semiconductor, other then those already listed, you will probably need to install the SoftDevice firmware on the board yourself in order to use it with TinyGo and the Go Bluetooth package.
Flashing the SoftDevice can sometimes be tricky. If you have [nrfjprog](https://www.nordicsemi.com/Software-and-Tools/Development-Tools/nRF-Command-Line-Tools) installed, you can erase the flash and flash the new BLE firmware using the following commands. Replace the path to the hex file with the correct SoftDevice, for example `s132_nrf52_6.1.1/s132_nrf52_6.1.1_softdevice.hex` for S132 version 6.
After that, don't reset the board but instead flash a new program to it. For example, you can flash the Heart Rate Sensor example using `tinygo` (modify the `-target` flag as needed for your board):
**The API is not stable!** Because many features are not yet implemented and some platforms (e.g. Windows and macOS) are not yet fully supported, it's hard to say what a good API will be. Therefore, if you want stability you should pick a particular git commit and use that. Go modules can be useful for this purpose.
**Q. Where can I get an introduction to Bluetooth Low Energy, GAP, GATT, etc.?**
A. Please see this excellent article from our friends at Adafruit: https://learn.adafruit.com/introduction-to-bluetooth-low-energy
**Q. What is a client and server in BLE?**
A. Please see https://devzone.nordicsemi.com/f/nordic-q-a/71/what-is-a-client-and-server-in-ble
**Q. Can a device be both a GATT client and GATT server?**
A. Yes, but this is not currently supported by Go Bluetooth. Current support is either to act as a central in client mode, or as a peripheral in server mode.
