Robotics Technologies microBus-Cam II Manual de usuario descargar pdf (Pagina 16)

Mobile Robots – Current Trends

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Fig. 26. Start and stop condition of two lines

This condition is a HIGH to LOW transition on the SDA line while SCL is HIGH. And the

I2C_STOP ( ) will produce the STOP condition. This procedure is a LOW to HIGH transition

on the SDA line while SCL is HIGH. Before the START condition will begin and after STOP

condition finished, the bus is considered to be always free condition, the both lines must be

HIGH. The next main function is I2C_ACK ( ). As shown in Fig.27, after the robot (master

device) sent data to slave device finished, the slave device must send back the

acknowledgement that the slave device received data already.

Fig. 27. Acknowledge condition

As shown in Fig.28, it shows a complete transfer cycle associated with a frame of data.

Firstly, the master initiates a write by asserting logic-0 at bit-8, where a slave address is

defined by the other 7-bits.

A acknowledge signal then follows from the slave as specified in

bit-9. The second and third bytes are the data and acknowledge signal. The 7-bits addressing

allows 127 devices on the I

C bus, by using 2-bytes address, which can be extended further.

The last two main functions are to control and get data from slave device. It consists of

I2C_SEND ( ) and I2C_RECEIVE ( ) function. This I2C_SEND ( ) function is sent always by

robot (master device) to control and set slave devices configuration and the I2C_RECEIVE ( )

function is also sent by robot to receive data from slave devices.

Fig. 28. Data transfer on the I

C bus

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Robotics Technologies microBus-Cam II Manual de usuario Pagina 16