Instructions

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4 Communication Interface

4.1 UART and RS232C interface

4.1.1 Physical Interface

The Universal Asynchronous Receiver/Transmitter (UART) takes bytes of data and transmits the

individual bits in a sequential fashion. And the interface level is TTL-level specification. The

communication between UART and PC is via TX, RX and GND pins. When using, the host's TX pin

should be connected to the device's RX pin; at the same time the host's RX pin should ne connected to

the device's TX pin.

RS232C is the UART interface which belongs to RS232C-level. The communication between

RS232C and PC is via TXD, RXD and GND pins. When using, the host's TXD pin should be

connected to the device's RXD pin, at the same time the host's RXD pin should be connected to the

device's TXD pin.

The communication protocol is byte oriented. Both sending and receiving bytes are in

hexadecimal format. The communication parameters are as follows:

Baud rate: 19200bps (default), 115200bps, 9600bps, 38400bps and 57600bps.

Start bits: 1 bit

Data bits: 8 bits

Stop bits: 1 bit

Parity check: None

Flow control: None

4.1.2 Communication Process

Host sends command to the slave, and the slave will execute the command once received it; then

the slave will send the result to the host. This is a command cycle.

It is meaningless to issue a new command before receiving the return message from the previous

command

4.2 I²C Interface

4.2.1 Physical Interface

I²C interface is a two-wire synchronous serial communication interface which belongs to

TTL-level specification. It uses only two bidirectional open-drain lines, Serial Data Line (SDA) and

Serial Clock (SCL), and could be pulled up with resistors 2.7K~10K to choose. The pulling up is very