Communication with barcode reading devices in the PROMOTIC system

The barcode reading devices can be connected to the computer:
- by serial interface
- by USB interface
- by network interface (Ethernet or WiFi)

In practice, we most often encounter some sort of serial connection of the reader to the computer. If the device is connected by standard serial interface RS232 then the PmChar communication driver can be used in Slave mode in the PROMOTIC system. In such case the PROMOTIC application is waiting for data from the barcode reader.

If the device is connected by USB interface then it is most probably identified as HID device in the Windows OS. It means that the barcode reader acts as standard input device as keyboard. From the PROMOTIC system point of view, the barcode readers in this mode can also be used, but from practical point of view it is quite difficult. The main reason is that in order to write some data into the PROMOTIC system a Pmg object allowing text entry must be focused in the application (e.g. the PmgString object in edit mode or the PmgWEdit object). It means that before each reading, the application user would have to set the focus on such Pmg object. Otherwise, PROMOTIC application would not capture the read code. This issue can be solved if there is a communication driver for the device that creates a virtual serial port in Windows OS. If such driver is available then barcodes can be read from that reader regardless of whether or not a Pmg object has the focus.

In addition to serial output readers, devices with network connectivity (Ethernet, WiFi) are also available. These readers are usually intelligent devices that can be programmed. For this reason, the use of these readers is beyond the scope of this documentation because the way the data is transferred from the reader to the desired applications can vary considerably from type to type.
PROMOTIC 9.0.25 SCADA system documentation MICROSYS, spol. s r.o.

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