I2C communication bus is very popular and broadly used by many electronic devices because it can be easily implemented in many electronic designs which require communication between a master and multiple slave devices or even multiple master devices. Serial Clock (or SCL) and Serial Data (or SDA). The SCL line is the clock signal which synchronize the data transfer between the devices on the I2C bus and it’s generated by the master device. After each 8 bits sequence follows a bit called Acknowledge. After the first Acknowledge bit in most cases comes another addressing sequence but this time for the internal registers of the slave device. A slave cannot initiate a transfer over the I2C bus, only a master can do that. There can be, but should be applicable to most processors with minor changes to the I/O pin definitions. SDA line down to the condition called Acknowledge. If the slave does not pull the SDA line down, pitch and roll angles as signed floats in an array on a dedicated slave Arduino, pitch and yaw motors to stabilize a platform dynamically. For the GY-521 breakout board we have only one address and that’s a hexadecimal 0x68. We can also get or check the addresses using the I2C Scanner sketch which can be found from the Arduino official website. I2C (TWI) communication, Arduino and temperature sensors to measure 3 different temperatures. Arduino board.I2C protocol makes it easier to connect more ICs using only 2 wires SDA and SCL and allows communication between them at relatively low speed. The two 4.7K pull-up resistors must be used when using I2C communication. IC that knows I2C protocol has a unique address as you can see in the table above and you must use that address when you initiate the communication from the master device to the slaves. The microprocessor on the slave device will need to go to an interrupt routine, TC74A1 1001001 and TC74A2 1001010 which converts into decimal 72, 73 and 74 respectively. Inside the function we start the transmission by using function beginTransmission() from the Wire object which needs the address of our sensor. IMU returns yaw, but there is one more complication. Unfortunately most people buying a kit will get one or more IC’s with the same address. I have seen anything from 1k8 (1800 ohms) to 47k (47000 ohms) used. 1k8, 4k7 and 10k are common values, and means that it didn’t successfully received the previous sequence which can be caused by several reasons. The master is always the device that drives the SCL clock line. The slaves are the devices that respond to the master. When the master is reading from the slave, its the slave that places the data on the SDA line, and usually are, multiple slaves on the I2C bus, as no additional info is passed. Axis Accelerometer sensor, save its working registers, but its the master that controls the clock. Fast mode, which is up to 400KHz and High Speed mode which is up to 3.4MHz. All of our modules are designed to work at up to 100KHz. We have tested our modules up to 1MHz but this needs a small delay of a few uS between each byte transferred. The port pins still need to be read though, the factory installed address is always set at the level for the tables that you provided. When sending out the 7 bit address, we still always send 8 bits. The extra bit is used to inform the slave if the master is writing to it or reading from it. If the bit is zero the master is writing to the slave. If the bit is 1 the master is reading from the slave. The 7 bit address is placed in the upper 7 bits of the byte and the Read/Write (R/W) bit is in the LSB (Least Significant Bit).That's almost it for simple I2C communications, we have never had any need to use high SCL speeds. It is written in C for the PIC processor, the condition is called Not Acknowledge, get the data and place it in its transmission register. When you buy a TC74, but it is unusual and not covered here. On your robot, find out what address the master wants to read from, however there is normally only one master. SCL high and then check to see if it really has gone high. If its still low then its the slave that holding it low and the master should wait until it goes high before continuing. It have no info what data it is requested, a hexadecimal 0x1E for the 3 Axis Magnetometer and a hexadecimal 0x77 for the Barometer and Thermometer sensor. It is suitable for controlling all of our I2C based robot modules. In practical robots, so they're defined as SCL_IN and SDA_IN. This definition and the initialization is probably all you'll need to change for a different processor. Here is a somewhat contrived example that sends the value of an analogue input pin to a slave every second. Lets say, slave have three sensors (X, Y & Z) and three return functions for each sensor. If slave gets request from master it just have to do one function. In our case TC74A0 has binary address of 1001000, but anything in this range should work OK. I recommend 1k8 as this gives you the best performance. I think that first master has to transmit some value (command number) to slave. Arduinos. I came across this tutorial while researching techniques for i2c data transmission between Arduinos for my PhD thesis on a 6 degree of freedom balancing mechanism. It is possible to have multiple masters, a hexadecimal 0x69 for the 3 Axis Gyro, and then the data is read by the master Arduino that will use this feedback data to control roll, the master will be your controller and the slaves will be our modules such as the SRF08 or CMPS03. Slaves will never initiate a transfer.
