After this the clock starts and each data bit is transferred during each clock pulse. The start condition occurs when data line drops low while the clock line is still high. Let’s take even closer look at these events. Right after the addressing sequences follows the data sequences as many until the data is completely sent and it ends with a special stop condition. After the first Acknowledge bit in most cases comes another addressing sequence but this time for the internal registers of the slave device. After each 8 bits sequence follows a bit called Acknowledge. So after a special start condition occurs comes the first 8 bits sequence which indicates the address of the slave to which the data is being sent. The normal way, with a lot of outputs (6) and wires (10).The data signal is transferred in sequences of 8 bits.The I2C-way, with only 2 data-lines (SDA and SCL) and 2 powerlines (+5V, GND).Set up the LCD's number of columns and rows: initialize the library with the numbers of the interface pins The library for this is “ LiquidCrystal.h” and that library is part of the Arduino-ide.Īll functions are explained on the website above. The I2C-way, with only 2 data-lines (SDA, the data-line and SCL, the clock-line) and 2 powerlines (+5V, GND).įor this we need to use a ‘IO expander’ like this.You can connect multiple devices on the I2C-bus, each device gets an address: This site explains the inner working of the I2C-protocol: You can address 128 devices (= 7bit addressing), from 0 to 127). Manufacturers gives these addresses to there I2C-devices. If the chip on your board is a PCF8574 T, then the I2C-addresses can lay in the range of 0x20 to 0x27. If the chip on your board is a PCF8574 AT, then the I2C-addresses can lay in the range of 0x3F to 0x38. This IO-module has a default I2C-address of 0x27, but you can change it yourself by changing the jumpers A0, A1 and A2 on the board (MARK the reverse order of A0A1A2 => A0A1A2).Į.g. In this picture you see that ‘jumper A0’ is soldered. So the I2C-address for this module is 0x26 or 0x3E. The library, called “ LiquidCrystal_I2C.h“, needed for these modules to work, can be found here.In the following example-code, there are 2 I2C-modules used with 2 different LCD-displays (16×2 and 20×4 display), also found partly in the LiquidCrystal_V1.2.1.zip.Ĭheck first if libraries aren’t available in the arduino-ide, before you download them.(Mark! Github always add ‘-master’ when you download a zip-file, unzip, rename the directory without ‘-master’, zip again and import the zip in arduino-ide).LiquidCrystal_I2C lcd1(0x20,16,2) // set the LCD address of the first lcd to 0x20 It can be used with the same functions as in “LiquidCrystal”, only initialisation of the LCD-object is different. LiquidCrystal_I2C lcd(0x20,16,4) // set the LCD address of the first lcd to 0x20Ĭonnecting your I2C-module to an Arduino via SDA and SCLīoth modules use the I2C bus, which makes connection very easy. If you’re using an Pro Mini-compatible the pins are A4 and A5 for data and clock, which are parallel to the main pins, as shown below: If you’re using an Arduino Mega the pins are D20 and D21 for data and clock: On Arduino Uno or compatible boards, these pins are A4 and A5 for data and clock: Moving on – first you will need to identify which pins on your Arduino or compatible boards are used for the I2C bus – these will be knows as SDA (or data) and SCL (or clock). The library to use for this ‘mjkdz’-module is “ LiquidCrystal_I2C.h” and can be found here: Other I2C-modules are available, like the ‘mjkds’-module: #WIRE H LIBRARY ARDUINO DOWNLOAD PRO# Mark the same name for the library, but initialisation is a bit different.And, would you mind taking a look at my code? I have the rc-car example code working well with my spark and motor shield. I have installed a robot arm and hand to my car, but haven’t quite gotten any servos to work.
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