Basler raL2048-48gm Manuel d'utilisateur télécharger pdf (Page 222)

Chunk Features AW00118302000

212 Basler racer GigE

11.8 CRC Checksum

The CRC (Cyclic Redundancy Check) Checksum feature adds a chunk to each acquired frame

containing a CRC checksum calculated using the X-modem method. As shown in Fig. 60 on

page 212, the checksum is calculated using all of the image data in the frame and all of the

appended chunks except for the checksum itself. The CRC chunk is always the last chunk

appended to the frame.

Fig. 60: CRC Checksum

Enabling the CRC Checksum and Retrieving Chunk Data

To enable the CRC checksum chunk:

 Use the Chunk Selector to select the CRC chunk.

 Use the Chunk Enable parameter to set the value of the chunk to true.

Once the CRC chunk is enabled, the camera will add a CRC chunk to each acquired frame.

To retrieve CRC information from a chunk appended to a frame that has been received by your PC,

you must first run the frame and its appended chunks through the chunk parser included in the pylon

API. Once the chunk parser has been used, you can retrieve the CRC information. Note that the

CRC information provided by the chunk parser is not the CRC checksum itself. Rather it is a true/

false result. When the frame and the appended chunks pass through the parser, the parser

calculates a CRC checksum based on the received frame and chunk information. It then compares

the calculated CRC checksum with the CRC checksum contained in the CRC checksum chunk. If

the two match, the result will indicate that the frame data is OK. If the two do not match, the result

will indicate that the frame is corrupted.

You can set the Chunk Selector and Chunk Enable parameter value from within your application

software by using the pylon API. You can also run the parser and retrieve the chunk data. The

following code snippets illustrate using the API to activate the chunk mode, enable the CRC

checksum chunk, run the parser, and retrieve the frame counter chunk data:

// Make chunk mode active and enable CRC chunk

Camera.ChunkModeActive.SetValue( true );

The chunk mode must be made active before you can enable the time stamp

feature or any of the other chunk features. Making the chunk mode inactive

disables all chunk features.

Frame Data

(including any required padding)

Chunk X

Data

Chunk Y

Data

Chunk

CRC

CRC checksum is calculated on this data

1 2 ... 217 218 219 220 221 222 223 224 225 226 227 ... 237 238

Pas de commentaire

Basler raL2048-48gm Manuel d'utilisateur Page 222