CFA633-RDI-KS datasheet(35/88 Pages) CRYSTAIFONTZ

35 / 88 page

Crystalfontz America, Inc.

Data Sheet Release Date 2012/02/21

www.crystalfontz.com

CFA633-RDI-KS LCD Module (Hardware v2.0 / Firmware s2v1)

February 2012

Page 35

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

automatically re-synchronize to the next valid packet in the event of any communications errors. Please follow the

algorithm in the sample code closely in order to realize the benefits of using the packet communications.

ABOUT HANDSHAKING

The nature of CFA633’s packets makes it unnecessary to implement traditional hardware or software handshaking.

The host should wait for a corresponding acknowledge packet from the CFA633 before sending the next command

packet. The CFA633 will respond to all packets within 250 mS. The host software should stop waiting and retry the packet

if the CFA633 fails to respond within 250 mS. The host software should report an error if a packet is not acknowledged

after several retries. This situation indicates a hardware problem — for example, a disconnected cable.

Please note that some operating systems may introduce delays between when the data arrives at the physical port from

the CFA633 until it is available to the user program. In this case, the host program may have to increase its timeout

window to account for the additional overhead of the operating system.

The CFA633 can be configured to send several types of report packets along with regular acknowledge packets. The

host should be able to buffer several incoming packets and must guarantee that it can process and remove packets from

its input buffer faster than the packets can arrive given the baud rate and the reporting configuration of the CFA633. For

any modern PC using reasonably efficient software, this requirement will not pose a challenge.

The report packets are sent asynchronously with respect to the command packets received from the host. The host

should not assume that the first packet received after it sends a command is the acknowledge packet for that command.

The host should inspect the type field of incoming packets and process them accordingly.

REPORT CODES

The CFA633 can be configured to report three items. The CFA633 sends reports automatically when the data becomes

available. Reports are not sent in response to a particular packet received from the host. The three report types are (1)

0x80: Key Activity, (2) 0x81: Fan Speed Report, and (3) 0x82: Temperature Sensor Report. Details are below.

0x80: Key Activity

If a key is pressed or released, the CFA633 sends a Key Activity report packet to the host. Key event reporting may be

individually enabled or disabled by command 23 (0x17): Configure Key Reporting (Pg. 50).

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