# Go Bluetooth

[![Go Bluetooth](./images/gobluetooth.png)](https://tinygo.org/bluetooth)

[![PkgGoDev](https://pkg.go.dev/badge/pkg.go.dev/tinygo.org/x/bluetooth)](https://pkg.go.dev/tinygo.org/x/bluetooth) [![Linux](https://github.com/tinygo-org/bluetooth/actions/workflows/linux.yml/badge.svg?branch=dev)](https://github.com/tinygo-org/bluetooth/actions/workflows/linux.yml) [![macOS](https://github.com/tinygo-org/bluetooth/actions/workflows/macos.yml/badge.svg?branch=dev)](https://github.com/tinygo-org/bluetooth/actions/workflows/macos.yml) [![Windows](https://github.com/tinygo-org/bluetooth/actions/workflows/windows.yml/badge.svg?branch=dev)](https://github.com/tinygo-org/bluetooth/actions/workflows/windows.yml)

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 works on typical operating systems such as [Linux](#linux), [macOS](#macos), and [Windows](#windows). It also works in the browser with [WASM](#wasm). 

By using [TinyGo](https://tinygo.org/), it can also be used running "bare metal" on microcontrollers produced by [Nordic Semiconductor](https://www.nordicsemi.com/), on the [Espressif](https://www.espressif.com/) ESP32-C3 and ESP32-S3 with their onboard radio, or on boards that have a Bluetooth co-processor that uses the [Bluetooth Host Controller Interface (HCI)](https://www.bluetooth.com/wp-content/uploads/Files/Specification/HTML/Core-54/out/en/host-controller-interface/host-controller-interface-functional-specification.html).

The Go Bluetooth package can be used to create both Bluetooth Low Energy Centrals as well as to create Bluetooth Low Energy Peripherals.

> [!IMPORTANT]
> You can help TinyGo with a financial contribution using OpenCollective. Please see https://opencollective.com/tinygo for more information. Thank you!

## 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
package main

import (
	"tinygo.org/x/bluetooth"
)

var adapter = bluetooth.DefaultAdapter

func main() {
	// Enable BLE interface.
	must("enable BLE stack", adapter.Enable())

	// Start scanning.
	println("scanning...")
	err := adapter.Scan(func(adapter *bluetooth.Adapter, device bluetooth.ScanResult) {
		println("found device:", device.Address.String(), device.RSSI, device.LocalName())
	})
	must("start scan", err)
}

func must(action string, err error) {
	if err != nil {
		panic("failed to " + action + ": " + err.Error())
	}
}
```

## Bluetooth Low Energy Peripheral

A typical Bluetooth Low Energy Peripheral would be a temperature sensor or heart rate sensor.

This example shows a peripheral that advertises itself as being available for connection:

```go
package main

import (
	"context"
	"time"

	"tinygo.org/x/bluetooth"
)

var adapter = bluetooth.DefaultAdapter

func main() {
  	// Enable BLE interface.
	must("enable BLE stack", adapter.Enable())

	ctx, cancel := context.WithCancel(context.Background())
	adapter.SetConnectHandler(func(device bluetooth.Device, connected bool) {
		if connected {
			println("device connected:", device.Address.String())
			return
		}

		println("device disconnected:", device.Address.String())
		cancel()
	})

  	// Define the peripheral device info.
	adv := adapter.DefaultAdvertisement()
	must("config adv", adv.Configure(bluetooth.AdvertisementOptions{
		LocalName: "Go Bluetooth",
  	}))
  
  	// Start advertising
	must("start adv", adv.Start())
	
	// Stop advertising to release resources
	defer adv.Stop()

	println("advertising...")
	<- ctx.Done()
}

func must(action string, err error) {
	if err != nil {
		panic("failed to " + action + ": " + err.Error())
	}
}
```

## Current support

|                                  | Linux              | macOS              | Windows            | WASM               | Nordic Semi        | ESP32 (NINA-FW)    | CYW43439 (RP2040-W) | ESP32-C3/S3 (espradio) |
| -------------------------------- | ------------------ | ------------------ | ------------------ | ------------------ | ------------------ | ------------------ | ------------------- | ---------------------- |
| API used                         | BlueZ              | CoreBluetooth      | WinRT              | WebBluetooth       | SoftDevice         | HCI         	    | HCI                 | HCI                    |
| Scanning                         | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark:  | :heavy_check_mark:     |
| Connect to peripheral            | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark:  | :heavy_check_mark:     |
| Write peripheral characteristics | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark:  | :heavy_check_mark:     |
| Receive notifications            | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark:  | :heavy_check_mark:     |
| Advertisement                    | :heavy_check_mark: | :x:                | :heavy_check_mark: | :x:                | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark:  | :heavy_check_mark:     |
| Local services                   | :heavy_check_mark: | :x:                | :heavy_check_mark: | :x:                | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark:  | :heavy_check_mark:     |
| Local characteristics            | :heavy_check_mark: | :x:                | :heavy_check_mark: | :x:                | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark:  | :heavy_check_mark:     |
| Send notifications               | :heavy_check_mark: | :x:                | :heavy_check_mark: | :x:                | :heavy_check_mark: | :heavy_check_mark: | :heavy_check_mark:  | :heavy_check_mark:     |

## Linux

Go Bluetooth support for Linux uses [BlueZ](http://www.bluez.org/) via the [D-Bus](https://en.wikipedia.org/wiki/D-Bus) interface. 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:

	git clone https://github.com/tinygo-org/bluetooth.git

### Compiling

After you have followed the installation, you should be able to compile/run the "scanner" test program:

	cd bluetooth
	go run ./examples/scanner

## macOS

Go Bluetooth support for macOS uses the [CoreBluetooth](https://developer.apple.com/documentation/corebluetooth?language=objc) libraries thanks to the https://github.com/tinygo-org/cbgo fork of the `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:

	git clone https://github.com/tinygo-org/bluetooth.git

### Compiling

After you have followed the installation, you should be able to compile/run the "scanner" test program:

	cd bluetooth
	go run ./examples/scanner

### Troubleshooting

There is a known issue with iTerm2 and the Bluetooth package. If you are getting a message like `abort: trap`, try whitelisting iTerm2 manually through System Settings -> Privacy & Security -> Bluetooth.

## Windows

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/saltosystems/winrt-go package.

### Installation

Only the Go compiler itself is needed to compile Go Bluetooth code targeting Windows.

You can obtain the Go Bluetooth package using Git:

	git clone https://github.com/tinygo-org/bluetooth.git

### Compiling

After you have followed the installation, you should be able to compile/run the "scanner" test program:

	cd bluetooth
	go run .\examples\scanner

## WASM

Go Bluetooth support for the browser uses the [Web Bluetooth API](https://developer.mozilla.org/en-US/docs/Web/API/Web_Bluetooth_API). Chrome and Edge support this API. See the [browser compatibility table](https://developer.mozilla.org/en-US/docs/Web/API/Web_Bluetooth_API#browser_compatibility).

WASM can only act as a BLE Central. The Web Bluetooth API has no peripheral role.

The API has some other limits that come from the browser:

* `Scan` opens the device picker of the browser instead of a continuous scan. The callback runs one time, for the device that the user selects.
* `Address` holds an opaque device ID instead of a MAC address.
* You must put every service that you want to use in `Adapter.RequestedServices` before you call `Scan`.
* The browser handles the security prompt, so the user must select the device.

### Installation

You can compile with [TinyGo](https://tinygo.org/getting-started/install/) or with the standard Go compiler.

You can obtain the Go Bluetooth package using Git:

	git clone https://github.com/tinygo-org/bluetooth.git

### Compiling

The "webbluetooth" example shows how to build and serve a page. See [examples/webbluetooth/README.md](./examples/webbluetooth/README.md) for the steps.

## Nordic Semiconductor

Go Bluetooth has bare metal support for several chips from [Nordic Semiconductor](https://www.nordicsemi.com/) 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.

### Installation

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/  

Once you have installed TinyGo, you can install the Go Bluetooth package by running:

	git clone https://github.com/tinygo-org/bluetooth.git

Check your desired target board for any additional installation requirements.

### Adafruit "Bluefruit" boards

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:

* [Adafruit Circuit Playground Bluefruit](https://www.adafruit.com/product/4333)
* [Adafruit CLUE](https://www.adafruit.com/product/4500)
* [Adafruit Feather nRF52840 Express](https://www.adafruit.com/product/4062)
* [Adafruit ItsyBitsy nRF52840](https://www.adafruit.com/product/4481)

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:

	tinygo flash -target circuitplay-bluefruit ./examples/circuitplay

### Seeed Studio XIAO nRF52840

The Seeed Studio Xiao nRF52840 uses the [UF2 bootloader](https://github.com/microsoft/uf2) with pre-loaded SoftDevice firmware, so it is very easy to use with TinyGo.

* [Seeed Studio XIAO nRF52840](https://wiki.seeedstudio.com/XIAO_BLE)

You can flash your TinyGo program like this:

    tinygo flash -target=xiao-ble ./examples/heartrate

### Other boards with UF2 bootloader

There are other boards with TinyGo support that use the same UF2 bootloader with pre-loaded SoftDevice. They include:

* [Nice Keyboards nice!nano](https://nicekeyboards.com/products/nice-nano-v1-0)
* [Makerdiary nRF52840 MDK USB Dongle](https://wiki.makerdiary.com/nrf52840-mdk-usb-dongle/)

### BBC micro:bit

#### Version 1

The [BBC micro:bit](https://microbit.org/) uses an nRF51 chip with a CMSIS-DAP interface.

You will need to install OpenOCD (http://openocd.org/) to flash the board.

First, flash the SoftDevice firmware by copying the .hex file to the device. For example (on Linux):

	cd bluetooth
    cp ./softdevice/s110_nrf51_8.0.0/s110_nrf51_8.0.0_softdevice.hex /media/yourusername/MICROBIT/

Once you have copied the SoftDevice firmware to the BBC micro:bit, you can then flash your TinyGo program:

    tinygo flash -target=microbit-s110v8 ./examples/heartrate

#### Version 2

The [BBC micro:bit v2](https://microbit.org/new-microbit/) uses an nRF52833 chip with a CMSIS-DAP interface.

You will need to install OpenOCD (http://openocd.org/) to flash this board.

You can use the BBC micro:bit v2 either as a peripheral only using the S113 SoftDevice, or else with both central and peripheral support using S140. Note that S140 does require more memory, leaving less for user programs.

To use S113, flash the SoftDevice firmware by copying the .hex file to the device. For example (on Linux):

	cd bluetooth
	cp ./softdevice/s113_nrf52_7.0.1/s113_nrf52_7.0.1_softdevice.hex /media/yourusername/MICROBIT/

Note that you should only have to do this one time. Do not reset the power on the board until you complete the next step.

Now that you have copied the SoftDevice firmware to the BBC micro:bit v2, you can flash your TinyGo program:

    tinygo flash -target=microbit-v2-s113v7 -programmer=cmsis-dap ./examples/heartrate

To use S140 with central and peripheral support, flash the SoftDevice firmware by copying the .hex file to the device. For example (on Linux):

	cd bluetooth
	cp ./softdevice/s140_nrf52_7.3.0/s140_nrf52_7.3.0_softdevice.hex /media/yourusername/MICROBIT/

Note that you should only have to do this one time. Do not reset the power on the board until you complete the next step.

Now that you have copied the SoftDevice firmware to the BBC micro:bit v2, you can flash your TinyGo program:

    tinygo flash -target=microbit-v2-s140v7 -programmer=cmsis-dap ./examples/heartrate-monitor

### Supported Chips

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 `softdevice/s132_nrf52_6.1.1/s132_nrf52_6.1.1_softdevice.hex` for S132 version 6.

    nrfjprog -f nrf52 --eraseall
    nrfjprog -f nrf52 --program path/to/softdevice.hex

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):

    tinygo flash -target=pca10040-s132v6 ./examples/heartrate

Flashing will normally reset the board.

## ESP32 (NINA)

Go Bluetooth has bare metal support for boards that include a separate ESP32 Bluetooth Low Energy radio co-processor. The ESP32 must be running the Arduino or Adafruit `nina_fw` firmware.

Several boards created by Adafruit and Arduino already have the `nina-fw` firmware pre-loaded. This means you can use TinyGo and the Go Bluetooth package without any additional steps required.

Currently supported boards include:

* [Adafruit Metro M4 AirLift](https://www.adafruit.com/product/4000)
* [Adafruit PyBadge](https://www.adafruit.com/product/4200) with [AirLift WiFi FeatherWing](https://www.adafruit.com/product/4264)
* [Adafruit PyPortal](https://www.adafruit.com/product/4116)
* [Arduino Nano 33 IoT](https://docs.arduino.cc/hardware/nano-33-iot)
* [Arduino Nano RP2040 Connect](https://docs.arduino.cc/hardware/nano-rp2040-connect)

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 Arduino Nano RP2040 Connect board with the example we provide that turns it into a BLE peripheral to act like a heart rate monitor:

	tinygo flash -target nano-rp2040 ./examples/heartrate

If you want more information about the `nina-fw` firmware, or want to add support for other ESP32-equipped boards, please see https://github.com/arduino/nina-fw

## ESP32, ESP32-C3 and ESP32-S3 (espradio)

Go Bluetooth has bare metal support for the onboard Bluetooth Low Energy radio in the Espressif ESP32, ESP32-C3 and ESP32-S3 chips. It uses the [espradio](https://github.com/tinygo-org/espradio) package, which speaks to the radio through the Virtual HCI (VHCI) interface.

This support requires compiling your programs using [TinyGo](https://tinygo.org/) version 0.42 or later. TinyGo sets the `espradio` build tag for the ESP32 targets, so you do not have to give the tag yourself.

On the original ESP32 only Bluetooth Low Energy is supported. The chip also has Bluetooth Classic (BR/EDR), which espradio does not use. The Bluetooth controller needs 64 KB of RAM at a fixed address on this chip, so a program that calls `Enable()` has a smaller heap than a program that does not.

Some boards carry a second ESP32 as a co-processor instead. For those boards, see the [ESP32 (NINA)](#esp32-nina) section.

Currently supported boards include:

* [Seeed Studio XIAO ESP32-C3](https://wiki.seeedstudio.com/XIAO_ESP32C3_Getting_Started/)
* [Seeed Studio XIAO ESP32-S3](https://wiki.seeedstudio.com/xiao_esp32s3_getting_started/)
* [M5Stamp C3](https://docs.m5stack.com/en/core/stamp_c3)
* [M5Stamp S3](https://docs.m5stack.com/en/core/M5Stamp%20S3)
* [M5Stack](https://docs.m5stack.com/en/core/basic)
* Other ESP32, ESP32-C3 and ESP32-S3 boards with a TinyGo target, such as `esp32-coreboard-v2`, `esp32-mini32`, `esp32c3-supermini`, `esp32s3-supermini`, `qtpy-esp32c3`, and `esp32c3-generic`

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 a XIAO ESP32-C3 board with the example we provide that turns it into a BLE peripheral to act like a heart rate monitor:

	tinygo flash -target xiao-esp32c3 ./examples/heartrate

### WiFi and Bluetooth together

The WiFi and Bluetooth radios share the same hardware. To use both, enable WiFi first, then enable the Bluetooth adapter:

```go
must("enable radio", espradio.Enable(espradio.Config{}))
must("enable BLE stack", adapter.Enable())
```

If you want more information about the `espradio` support, please see https://github.com/tinygo-org/espradio

## CYW43439 (RP2040-W)

Go Bluetooth has bare metal support for boards that include a separate CYW43439 Bluetooth Low Energy radio co-processor.

Currently supported boards include:

* [Raspberry Pi Pico RP2040-W](https://www.raspberrypi.com/documentation/microcontrollers/raspberry-pi-pico.html#raspberry-pi-pico-w)
* [Pimoroni Badger2040-W](https://shop.pimoroni.com/products/badger-2040-w)

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 a Pico RP2040-W board with the example we provide that turns it into a BLE peripheral to act like a heart rate monitor:

	tinygo flash -target pico-w ./examples/heartrate

If you want more information about the `cyw43439` support, please see https://github.com/soypat/cyw43439

## API stability

**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.

Some things that will probably change:

  * Add options to the `Scan` method, for example to filter on UUID.
  * Extra options to the `Enable` function, to request particular features (such as the number of peripheral connections supported).

This package will probably remain unstable until the following has been implemented:

  * Scan filters. For example, to filter on service UUID.
  * Bonding and private addresses.
  * Full support for all features at least two desktop operating systems.
  * Maybe some Bluetooth Classic support, such as A2DP.

## Contributing

Your contributions are welcome!

Please take a look at our [CONTRIBUTING.md](./CONTRIBUTING.md) document for details.

## Frequently Asked Questions

**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.

## License

This project is licensed under the BSD 3-clause license, see the LICENSE file for details.

The SoftDevices from Nordic are licensed under a different license, check the license file in the SoftDevice source directory.