Arduino Tutorial => Multiple Slaves

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arduino

• Getting started with arduino
• Awesome Book
• Awesome Community
• Awesome Course
• Awesome Tutorial
• Awesome YouTube
• Analog Inputs
• Arduino IDE
• Audio Output
• Bluetooth Communication
• Data Storage
• Digital Inputs
• Digital Output
• Functions
• Hardware pins
• How Python integrates with Arduino Uno
• How to store variables in EEPROM and use them for permanent storage
• I2C Communication
• Multiple slaves
• Interrupts
• Libraries
• Liquid Crystal Library
• Loops
• MIDI Communication
• PWM - Pulse Width Modulation
• Random Numbers
• Serial Communication
• Servo
• SPI Communication
• Time Management
• Using Arduino with Atmel Studio 7
• Variables and Data Types

arduino I2C Communication Multiple slaves

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Example

The following example shows how the master can receive data from multiple slaves. In this example the slave sends two short numbers. The first one is for temperature, and the second one is for moisture. Please notice that the temperature is a float (24.3). In order to use only two bytes and not four (float is four bytes), I multiple the temperature in 10, and save it as a short. So here is the master code:

#include <Wire.h> #define BUFFER_SIZE 4 #define MAX_NUMBER_OF_SLAVES 24 #define FIRST_SLAVE_ADDRESS 1 #define READ_CYCLE_DELAY 1000 byte buffer[BUFFER_SIZE]; void setup() { Serial.begin(9600); Serial.println("MASTER READER"); Serial.println("*************"); Wire.begin(); // Activate I2C link } void loop() { for (int slaveAddress = FIRST_SLAVE_ADDRESS; slaveAddress <= MAX_NUMBER_OF_SLAVES; slaveAddress++) { Wire.requestFrom(slaveAddress, BUFFER_SIZE); // request data from the slave if(Wire.available() == BUFFER_SIZE) { // if the available data size is same as I'm expecting // Reads the buffer the slave sent for (int i = 0; i < BUFFER_SIZE; i++) { buffer[i] = Wire.read(); // gets the data } // Parse the buffer // In order to convert the incoming bytes info short, I use union union short_tag { byte b[2]; short val; } short_cast; // Parse the temperature short_cast.b[0] = buffer[0]; short_cast.b[1] = buffer[1]; float temperature = ((float)(short_cast.val)) / 10; // Parse the moisture short_cast.b[0] = buffer[2]; short_cast.b[1] = buffer[3]; short moisture = short_cast.val; // Prints the income data Serial.print("Slave address "); Serial.print(slaveAddress); Serial.print(": Temprature = "); Serial.print(temprature); Serial.print("; Moisture = "); Serial.println(moisture); } } Serial.println("*************************"); delay(READ_CYCLE_DELAY); } }

And now the slave code:

#include <Wire.h> #include <OneWire.h> #include <DallasTemperature.h> //===================== // This is the hard-coded address. Change it from one device to another #define SLAVE_ADDRESS 1 //===================== // I2C Variables #define BUFFER_SIZE 2 #define READ_CYCLE_DELAY 1000 short data[BUFFER_SIZE]; // Temprature Variables OneWire oneWire(8); DallasTemperature temperatureSensors(&oneWire); float m_temperature; // Moisture Variables short m_moisture; // General Variables int m_timestamp; void setup() { Serial.begin(9600); Serial.println("SLAVE SENDER"); Serial.print("Node address: "); Serial.println(SLAVE_ADDRESS); Serial.print("Buffer size: "); Serial.println(BUFFER_SIZE * sizeof(short)); Serial.println("***********************"); m_timestamp = millis(); Wire.begin(NODE_ADDRESS); // Activate I2C network Wire.onRequest(requestEvent); // Set the request event handler temperatureSensors.begin(); } void loop() { if(millis() - m_timestamp < READ_CYCLE_DELAY) return; // Reads the temperature temperatureSensors.requestTemperatures(); m_temperature = temperatureSensors.getTempCByIndex(0); // Reads the moisture m_moisture = analogRead(A0); } void requestEvent() { data[0] = m_temperature * 10; // In order to use short, I multiple by 10 data[1] = m_moisture; Wire.write((byte*)data, BUFFER_SIZE * sizeof(short)); }

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Ask any arduino Questions and Get Instant Answers from ChatGPT AI: ChatGPT answer me! PDF - Download arduino for free Previous Next This modified text is an extract of the original Stack Overflow Documentation created by following contributors and released under CC BY-SA 3.0 This website is not affiliated with Stack Overflow SUPPORT & PARTNERS

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