This document discusses using mbed and Bluetooth Low Energy (BLE) for Internet of Things (IoT) development. It outlines some issues with traditional chip vendor SDKs and promotes mbed as an alternative that provides a common development environment across multiple boards. Key points covered include mbed's online IDE, supported boards, new mbed OS features like automatic battery management, and examples for building BLE beacon and sensor services that can interact with web applications. Code samples are provided for initializing BLE services and characteristics and updating values. Physical web and Eddystone beacon protocols are mentioned as ways to broadcast URLs from embedded devices.

1. Developing with
Bluetooth World
15 March 2016
mbed and Bluetooth LE

2. @janjongboom
Developer Evangelist
Internet of Things

4. Choosing a vendor, not a chip
own SDKs, IDEs, programming patterns

5. Unstreamlined
Single-platform tools
No code sharing
Lack of libraries, documentation

6. (since 2009)
mbed

7. Online IDE
Code sharing
Single way of building for all targets

8. 91 boards supported
~200 staff working on it
170,000+ developers

9. Focused on prototyping

10. Building on top of mbed
New release: mbed OS

11. mbed OS
Open source embedded platform
Operating system for microcontrollers
Rock-solid HAL and libraries (e.g. Bluetooth)

12. One year on AA battery 0.137 mA

13. Differences
Task scheduler
Automatic battery management
The embedded event loop is dead
while (1) {
delay_ms(1);
}

14. yotta
Build tools and library management
Cross-platform (Windows, OS X, Linux, Browser)
Easily integrated in own workflow
Coming to uVision and new online IDE

15. Let's build something...

16. Get a board
Maxim MAX32610-based (???)
Nordic nRF51822-based
ST Nucleo IDB04A1

17. configure
Install yotta yottadocs.mbed.com
Initialize project yotta init
Set up target yotta target nrf51dk-gcc
Add BLE yotta install ble

18. github.com/ARMmbed/ble-examples

19. Built-in GATT services
(e.g. heart rate)

20. 1 #include "ble/BLE.h"
2
3 const static char DEVICE_NAME[] = "HRM";
4 static const uint16_t uuid16_list[] = {GattService::UUID_HEART_RATE_SERVICE};
5
6 static uint8_t hrmCounter = 100; // init HRM to 100bps
7
8 auto hrServicePtr = new HeartRateService(
9 ble, hrmCounter, HeartRateService::LOCATION_FINGER);
10
11 /* snip.. configuration */
12 ble.gap().setAdvertisingInterval(1000);
13 ble.gap().startAdvertising();

21. 1 void updateHr(void)
2 {
3 if (BLE::Instance().getGapState().connected) {
4 hrmCounter++;
5
6 if (hrmCounter == 175) {
7 hrmCounter = 100;
8 }
9
10 hrServicePtr->updateHeartRate(hrmCounter);
11 }
12 }
13
14 void app_start(int, char **)
15 {
16 Scheduler::postCallback(updateHr).period(minar::milliseconds(500));
17 }

22. Building
$ yotta build
$ cp build/heartrate.hex /Volumes/MBED

24. 1 class ButtonService {
2 uint16_t BUTTON_SERVICE_UUID = 0xA000;
3 uint16_t BUTTON_STATE_CHARACTERISTIC_UUID = 0xA001;
4
5 ButtonService(BLE &_ble, bool buttonPressedInitial) :
6 ble(_ble), buttonState(BUTTON_STATE_CHARACTERISTIC_UUID,
7 GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_NOTIFY)
8 {
9 GattCharacteristic *charTable[] = { &buttonState };
10 GattService service(ButtonService::BUTTON_SERVICE_UUID, /*chars*/);
11 ble.gattServer().addService(buttonService);
12 }
13
14 void updateButtonState(bool newState) {
15 ble.gattServer().write(buttonState.getValueHandle(), newState);
16 }
17
18 BLE &ble;
19 ReadOnlyGattCharacteristic<bool> buttonState;
20 };

26. Physical Web
Walk up and use anything

27. Physical Web beacon
http://goo.gl/a1b4cd
(Eddystone protocol)

28. Official Eddystone library
for mbed OS

29. 1 #include "EddystoneService.h"
2
3 auto eddyServicePtr = new EddystoneService(
4 ble, defaultAdvPowerLevels, radioPowerLevels);
5
6 const char* url = "http://mbed.com";
7 eddyServicePtr->setURLData(url);
8
9 eddyServicePtr->startBeaconService();

30. Web Bluetooth
GATT from JS
Some great demo's: http://thebubbleworks.com

31. http://rollingspider.xyz/aa73bc21

32. http://meeting.arm.com/tesla

33. One problem...
Eddystone is non-connectable
No service UUIDs in frames
... send two frames!

34. http://blog.mbed.com/post/137093070607/

36. End-to-end
Demo time!

37. Juggling visualizer
On device, accelerometer service
Sends out URL
Web app that plots values over time

39. http://github.com/web-bluetooth/juggling

40. Get hacking!

41. Thank you!
http://janjongboom.com