Developers guide

Chapter 14: Scanners
Scanner Events
Psion Teklogix Mobile Devices SDK Developers Guide 152
The following diagram shows the timing sequence for a software initiated bar code scan:
Figure 14.2 Software Initiated Scanner Timing Sequence
There are four possible outcomes for a bar code scan:
• The scan is successful.
• The scan times out.
• The scan is cancelled.
• The scan fails.
The scan is successful: The bar code is scanned and decoded before the scanner trigger is re-
leased. The decoded bar code is displayed on the screen of the hand-held computer, as well as
being returned as a character string to the calling program.
The scan times out: The scan beam on time expires and the scanner beam is turned off before the
bar code has been decoded. The scanner trigger must be released before another scan can be initi-
ated. This condition can be caused by the following:
• Scanning an unsupported bar code symbology.
• Scanning a disabled bar code symbology.
• Scanning a damaged or otherwise unreadable (out of specification) bar code.
• Scanning something that is not a bar code.
The scan is cancelled: The scanner trigger is released before the bar code has been decoded.
The scan fails: No bar code data is generated by the scan. The cause is not known.
14.5 Scanner Events
The following types of scan events are generated (check the API library documentation for the
name of the event and the values returned in each of the development languages):
Typically 0.5 sec.
Time
Scan initiated
Dot time
Scan beam on time
Soft Scan Timeout
Time
Typically 0.5 sec.
Time
Scan initiated
Dot time
Scan beam on time
Soft Scan Timeout
Time
Event Type Generated When... Returns
Scan complete Scan is successful
Scan failed Scan is not successful Scan cancelled
Scan timed-out
Scan failed