TC63 AT Command Set

19.7 AT^SSPI

s

19.7.2Transmitting Data over AT Interface

This section provides information on the protocol used for data transmission to or from I²C devices and explains the data mode. It is assumed that you are familiar with the I²C specification.

Throughout this section the following document conventions are used to mark the direction of send and receive: Transfer Message: AT I²C device driver

Response Message: AT I²C device driver

Channel Open / Close:

To change from command mode to data mode use the AT^SSPI write command. To close down the channel and return to command mode send the ASCII code # (0x23).

ASCII Protocol for I²C communication over AT interface:

The protocol allows using a Terminal program for the communication between the module and the I²C slave device. To visualize transferred characters and response data it is recommended to run the Terminal program in chat mode or to switch on local echo.

For transfer and response, special characters are defined, such as Start and Stop to mark a single message and Close to disconnect the data channel. All valid special characters are listed below:

Table 19.3: Special characters for ASCII coding

 

 

 

 

 

 

 

 

 

Direction

Function in protocol

Special

Hex value

Description

 

AT - Driver

 

character

 

 

 

Start Transfer Message

<

0x3C

Special character sent to the I²C

driver to

 

 

 

 

start sending.

 

Stop Transfer Message

>

0x3E

Special character sent to the I²C

driver to

 

 

 

 

stop sending.

 

Channel Close

#

0x23

For signalling.

 

 

 

 

 

Channel Close can be sent any time inside

 

 

 

 

or outside a transmit or receive message.

 

 

 

 

Causes the transfer to be aborted and

 

 

 

 

takes the ME back to AT command mode.

Start Response Message

{

0x7B

Special character sent to the I²C

driver to

 

 

 

 

mark the beginning of a Response Mes-

 

 

 

 

sage.

 

Stop Response Message

}

0x7D

Special character sent to the I²C

driver to

 

 

 

 

mark the end of a Response Message.

Protocol error

!

0x21

For signalling.

 

 

 

 

 

Reports to the AT interface that the Trans-

 

 

 

 

fer Frame does not comply with the proto-

 

 

 

 

col definition (syntax error).

 

Transmission OK

+

0x2B

Notifies the AT interface that data were

 

(in I²C protocol referred to

 

 

successfully transmitted or the I²C Slave

 

as ACK)

 

 

Address was recognized.

 

Transmission error

-

0x2D

Notifies the AT interface that data transmis-

 

(in I²C protocol referred to

 

 

sion failed or the I²C Slave Address was

 

as NAK)

 

 

not recognized. On the I²C bus, the faulty

 

 

 

 

data byte (16 bit byte counter) is identified

 

 

 

 

as well.

 

 

 

 

 

 

 

TC63_ATC_V00.490

Page 453 of 501

5/24/05

Confidential / Draft - Do not copy

 

 

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Siemens TC63 manual Transmitting Data over AT Interface, Channel Open / Close