Photon 2 BLE Syntax

Photon 2 BLE Syntax

Overview

• Present basic guide to receiving data from phone app to Photon 2
• To simplify some of the code, we will be using a custom-built BLE library
• For more in-depth information including sending from Photon 2 and connecting to multiple devices
  • Particle BLE Docs
  • Particle BLE Tutorials

Receiving Data with Photon 2

void onDataReceived(const uint8_t* data, size_t len,
                    const BlePeerDevice& peer,void* context);

• After a BLE connection is made, onDataReceived is the event handler that is called when data is received by the Photon 2
• We are only concerned with the first two parameters: data and len

Receiving Data with Photon 2

• const uint8_t* data
  • uint_8 is the variable type for unsigned byte (8 bits)
  • const uint8_t* is a pointer, which in C++ indicates the start of an array
  • data represents an array of bytes
• size_t len represents the number of bytes that were received

Handling Pointers

• Pointers are powerful, wonderful, and complex C++ tool
• However, we are just going to treat data as an array

Example

• Let’s say the onDataReceived parameter len equal 5

• We can then treat the data variable as an array of bytes

  Serial.println("First element: " + String(data[0]));
    
  uint8_t thirdByte = data[2];
    
  uint8_t sixthByte = data[5];  //ERROR! len = 5; arrays start at 0
  

Bluefruit App

• When sending data over Bluetooth, data will be packaged in bytes
• It is important to know ahead of time the format of the data
• We will be using Adafruit’s Bluefruit app to communicate with Photon 2
• The data structure is specific to this app and doesn’t apply to other apps
• For reference: Adafruit Bluefruit Guide

Bluefruit App Commands

• Each command from the app is a series of bytes
  • IMPORTANT: char variables or single letters are also bytes
• The first byte is the char of !
• The second byte signals the type of command
• For example
  • B means a button on the control pad was pressed
  • L means that location data from the phone is being send

Bluefruit App Control Pad

Bluefruit App Control Pad

• Button presses send 5 bytes

[‘!’] [‘B’] [BUTTON_CODE] [BUTTON_STATE] [CRC]

• BUTTON_CODE represents the symbol pressed (e.g. button was would be '1')
• BUTTON_STATE represents if the button was pressed ('1') or released ('0')
• CRC is an error-checking byte (we won’t worry about it for now)

Examples

• Pressing the 3 button means that the data “array” would have the values

[‘!’] [‘B’] ['3'] ['1'] [CRC]

• Releasing the Up arrow button means that the data “array” would have the values

[‘!’] [‘B’] ['5'] ['0'] [CRC]

Lab: Control Fan

• Use Bluefruit app to control a DC motor and servo motor
• Download starting code
  • Go to https://bit.ly/ProjectZip
  • Paste the following link into the top right https://github.com/reparke/ITP348-Physical-Computing/tree/main/_exercises/week09/ble_fan_start
• In Bluefruit app, connect to over UART (listed as “controller”)

Lab Wiring Guide

On-board LED    D7
Potentiometer   A1
Servo           A2

Motor Controller
 PWMA           A5 
 AIN2           D4 
 AIN1           D3 
 VCC            3v3
 GND            GND
 VM             3v3
 STBY           3v3

Lab: Control Fan (part 1)

• Specifications
  • When “1” is pressed down, on-board LED D7 will blink twice
  • When “2” is pressed down, on-board LED D7 will turn on
  • When “2” is released, on-board LED D7 will turn off
• Reference: Adafruit Bluefruit Guide

Lab: Control Fan (part 2)

• Specifications
  • When “RIGHT” is pressed down, rotate servo (by fixed amount) clockwise
  • When “LEFT” is pressed down, rotate servo (by fixed amount) counter clockwise
  • When “UP” is pressed down, speed up motor (by fixed amount)
  • When “DOWN” is pressed down, slow motor(by fixed amount)
  • Optional challenge:
    • When “3” is pressed down, change direction of DC motor
    • When “4” is pressed, turn on fan auto mode
• Reference: Adafruit Bluefruit Guide

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Demo Projects

• The following two completed projects are provided
• Each involves using a phone app to communicate with Photon 2 via Bluetooth
• The coding in these examples is much more complicated than the previous exercises

Demo #1: Control RGB LED with Phone Accelerometers (part 1)

• Use Bluefruit app to send accelerometer data from phone to Photon 2
• Control RGB LED colors with accelerometer data
• Download starting code
  • Go to https://bit.ly/ProjectZip
  • Paste the following link into the top right https://github.com/reparke/ITP348-Physical-Computing/tree/main/_exercises/week09/ble_uart_rgb_accel_example

Demo #1: Control RGB LED with Phone Accelerometers (part 2)

• Using Bluefruit, connect to over UART (listed as “controller”) in app
• Enable “accelerometer” in app
• Photon 2 sketch will receive accelerometer data (X, Y, Z) from phone, convert readings to PWM (0-255), and change LED color
• Reference: Adafruit Bluefruit Guide

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Demo #2: Read Health Thermometer Service (part 1)

• Send temperature data from Photon 2 to phone via nRF Toolbox

• Photon 2 is using Bluetooth health thermometer service

• Download starting code

  • Go to https://bit.ly/ProjectZip

  • Paste the following link into the top right https://github.com/reparke/ITP348-Physical-Computing/tree/main/_exercises/week09/ble_health_temp_final

Demo #2: Read Health Thermometer Service (part 2)

• Using nRF Toolbox app, connect to over HTM (“health thermometer”)
• Photon 2 sketch will send temperature data to app
• Reference: Particle Guide

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References

• Adafruit Bluefruit Guide

Credits

• Images created with Fritzing