CFA633-RDI-KU datasheet(33/86 Pages) CRYSTAIFONTZ

33 / 86 page

Crystalfontz America, Inc.

Data Sheet Release Date 2012/02/21

www.crystalfontz.com

CFA633-RDI-KU LCD Module (Hardware v2.0 / Firmware u2v1)

February 2012

Page 33

PACKET STRUCTURE

All communication between the CFA633 and the host takes place in the form of a simple and robust CRC checked

packet. The packet format allows for very reliable communications between the CFA633 and the host without the

traditional problems that occur in a stream-based serial communication (such as having to send data in inefficient ASCII

format, to “escape” certain “control characters”, or losing sync if a character is corrupted, missing, or inserted).

All packets have the following structure:

type

is one byte, and identifies the type and function of the packet:

TTcc cccc

|||| ||||--Command, response, error or report code 0-63

||---------Type:

00 = normal command from host to CFA633

01 = normal response from CFA633 to host

10 = normal report from CFA633 to host (not in

direct response to a command from the host)

11 = error response from CFA633 to host (a packet

with valid structure but illegal content

was received by the CFA633)

data_length

specifies the number of bytes that will follow in the data field. The valid range of data_length is 0 to

18.

data

is the payload of the packet. Each type of packet will have a specified data_length and format for data as

well as algorithms for decoding data detailed below.

CRC

is a standard 16-bit CRC of all the bytes in the packet except the CRC itself. The CRC is sent LSB first. At the

port, the CRC immediately follows the last used element of data []. See APPENDIX C: DEMONSTRATION SOFT-

WARE AND SAMPLE CODE (Pg. 69) for details.

The following C definition may be useful for understanding the packet structure.

typedef struct

{

unsigned char

command;

unsigned char

data_length;

unsigned char

data[MAX_DATA_LENGTH];

unsigned short

CRC;

}COMMAND_PACKET;

On our website, Crystalfontz supplies a demonstration and test program, 633_WinTest along with its C source code.

Included in the 633_WinTest source is a CRC algorithm and an algorithm that detects packets. The algorithm will

NOTE

Reconciling packets is recommended rather than using delays when communicating with the module.

To reconcile your packets, please ensure that you have received the acknowledgement packet from

the packet most recently sent before sending any additional packets to the LCD module. This practice

will guarantee that you will not have any dropped packets or missed communication with the LCD

module.

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