Here, for example, pins 21 (SDA) and 22 (SCL) are manually assigned to the I2C bus by calling the method like this Wire.begin(pin_sda, pin_scl). However, the SDA and SCL pins can be specified. We cannot therefore create an I2C network to communicate several ESP32 or ESP8266 together. Wire.begin(0x09) Limitations of the Wire.h library for ESP32 and ESP8266Īdapting the Wire.h library for ESP32 and ESP8266 development boards does not allow assigning an address to secondary equipment. However, the SDA and SCL pins cannot be manually specified. We will see other useful methods in the following examples Limitations of the Wire.h library for Arduino boardsįor Arduino boards, the Wire.begin() method allows you to manually specify the address of a device. Wire.endTransmission() is used to close communication with the equipment The conversion of a character string into byte is managed by the library
Arduino wire library choose bus series#
Wire.write(string) a string to send as a series of bytes. Wire.write(value) a value to send on a byte Several data formats are supported by the library Wire.write(data_to_send) allows data to be sent to the device specified previously. Wire.beginTransmission(i2c_address) is used to start sending data to the device whose address is passed as a parameter. To put it simply, the Wire.h library has 4 main methods. However, it is possible to use the Wire.h library to develop our own communication protocol between two (or more) Arduino (or any other microcontroller for that matter) Wire.begin() Ĭommercial I2C modules have a library which takes care of recovering data which greatly facilitates development work since we do not have to deal with decoding the packets sent. This parameter will be used for example when developing an I2C network between several Arduinos. The address corresponds to the address that one wishes to assign to the secondary equipment. On Arduino, the pins are not specified, the library uses the default pins for the targeted development board. The i2c bus is initialized using the Wire.begin (address) method. To use the I2C bus in an Arduino project, all you have to do is declare the wire library at the start of the code. The version dedicated to ESP32 and ESP8266 is installed at the same time as the SDK. It is a standard library which does not require any additional installation. The i2c bus is supported by the Wire.h library which has also been ported to ESP32 and ESP8266. Presentation of the Wire.h library for Arduino, ESP32 and ESP8266 (*) Do not use the pins marked SDA and SCL on the Arduino Uno. It can be assigned by programming (rarely) or by modifying the circuit (using a solder jumper or by applying a pre-defined voltage). Usually a secondary I2C address is available. There is no standard, but manufacturers organize themselves not to use an address already used by an existing component. This address is assigned by the component manufacturer. I2C addressesĮach secondary device therefore has a unique address which takes the form of a hexadecimal string, for example 0圆9.
Most of the time, the speed is less than 1 Mbit/s, in general it is between 100 and 400 kbit/s for the sensors. The maximum speed is imposed by the manufacturer.
Note that it is very rare to exceed 10 devices per assembly in the majority of connected object projects. The two lines must be connected to a reference voltage (Vdd) via pull-up resistors. The signal is generated only by the main equipmentįrom an electrical point of view, all equipment must be connected to the same GND electrical ground.
Most of the time, the I2C bus consists of a main device and one or more secondary devices, but the standard allows more complex organizations.
Arduino wire library choose bus serial#
The I2C bus is therefore an improvement in serial communication intended to communicate home automation accessories developed from the 1980s by Philipps. However, we will not discuss the technical operation of the I2C bus which is already very well explained on this Wikipedia page. In this article, we will discuss the operating principle of the Wire.h library, which allows Arduino to communicate easily with each other.
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