Newland EM3000 Spezifikationen PDF herunterladen (Seite 35)

nlscan.com

Page 26

Barcode Message

Software Interface

The message upload format is in binary. It is the binary value of the decoded barcode value

including prefix, suffix, and so on.

There are three methods to determine the end of barcode message.

Method 1: LED Signal

If a valid reading is found, the default function is to send a PMW signal to BUZ line and the

decoded barcode message will be sent through the serial out line.

After the barcode message is transmitted, the LED line will be pulled low for 1ms, then

high for 50ms, low for 50ms, high for 50ms in turn. Finally it will be pulled low for 1ms as

end. EM3000's application program controls LED signal level. If prgram enables LED, the

signal level will go as shown in the left diagram below. If disables, it will go as shown in the

right diagram below. To start next reading, the trigger line must be pulled high before next

trigger to read.

Suggestion: If LED signal is used to decide if a reading is successful, please use LED

positive edge interrupt. Positive edge A is as shown in diagrams above. And the programs in

the Host should watch and store the data through by serial port in cache. When positive edge

A appears in LED signal, data has been transmitted. Now the Host should decide if data is

stored. If yes, it must be a complete barcode message. It should be transmitted to the Host as

soon as possible. If no, please go on reading.

Method 2: Inter-Character Timeout

Host could use inter-character timeout to determine the end of data upload. An inter-

character timeout means the longest delay time between 2 consecutive (binary) characters

in a sequence of (binary) characters sent over serial line. It is usually enabled only after the

first character is received to avoid unwanted timeout events during the waiting of a message.

The inter-character timeout value should be set to about 5 times of a character’s

transmission time. When the inter-character timeout occurs, it is the end of data upload. For

example, 5 ms can be used as an inter-character timeout for the baud rate of 9600, 8 data bit,

no parity bit, and one stop bit.

Method 3 : Message packing

Message pack uses framing protocol format. Factory default has message pack disabled.

More detail about message Pack option is in next chapter.

1 2 ... 30 31 32 33 34 35 36 37 38 39 40 ... 158 159

Keine Kommentare

Newland EM3000 Spezifikationen Seite 35