Weight Scale Interfacing Example: Digi D770
The following script communicates with a Digi Model D770 weight scale. During invoicing or other transaction related activities a function key can be programmed to launch the script below, using the ScriptRun() function.
Example Interfacing Script
* D770 scale interface
DECLARE nWeight TYPE Numeric
DECLARE cResponse TYPE String
DECLARE cDevice TYPE String
nWeight := 0
cResponse := ""
cDevice := "D770"
*
IF ComOpen(cDevice)
* ENQ
If .Not. ComWrite(cDevice, Chr(5))
Goto ERROR
Endif
* read response ( 1 char, no terminator, wait max.1 sec )
cResponse := ComRead(cDevice, 1,, 1)
If IsEmpty(cResponse)
Echo("No response from the scale")
Goto ERROR
Endif
*
* NAK received
If cResponse == Chr(21)
Echo("Transmission error")
Goto ERROR
Endif
*
* NUL received
If cResponse == Chr(0)
Echo("Scale not stable")
Goto ERROR
Endif
*
* CAN received
If cResponse == Chr(24)
Echo("No new weight on the scale")
Goto ERROR
Endif
*
* ACK received
If cResponse == Chr(6)
* request the weight - send DC1
If .Not. ComWrite(cDevice, Chr(17))
Goto ERROR
Endif
* wait for up to 9 characters, timeout 1 sec.
cResponse := ComRead(cDevice, 9,, 1)
If IsEmpty(cResponse)
Echo("No response from the scale")
Goto ERROR
Endif
* NAK received
If cResponse == Chr(21)
Echo("Transmission error")
Goto ERROR
Endif
* ACK received (unexpected)
If cResponse == Chr(6)
Echo("Transmission error")
GoTo ERROR
Endif
* end of transmission
If cResponse == Chr(13)
Goto ERROR
Endif
If Len(cResponse) == 9
nWeight := Val(Substr(cResponse, 3, 5 )) / 1000
Endif
Else
Echo("Unknown response from the scale")
Goto ERROR
Endif
Endif
:ERROR
If .Not. Empty(ComError(cDevice))
Echo(ComError(cDevice))
Endif
ComClose(cDevice)
* echo(Str(nWeight))
Return nWeight
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Related Topics:
Serial Communication Functions
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