This section provides information about how devices respond with status information when the various types of connections are used.  Understanding the different types of device status messages under various connection scenarios is the key to being able to print your labels successfully.  You are encouraged to read the following information carefully.

Query Status Request

Query requests are only supported on serial (COM) ports.  If you are using a serial connection, a query status is very helpful to troubleshoot whether you have the proper cable, baud, parity, stop bits, etc.

Query Status Requests with Serial Printers are a two-way communication query between Loftware Label Manager and any printer that supports statusing.  Statusing determines if Loftware Label Manager is communicating correctly with the printer, whether or not the printer is “on-line” or in an error state, and other hardware information such as firmware version and available memory.

To check device status, use the File | Device Status menu command or the F7 shortcut key.  A Device Status dialog box is displayed.

Figure 2-K: Device Status Dialog Box

After clicking the Status box, Loftware Label Manager sends a status request to the device and, if successful, returns a message box.

If the device is in an error state, an error code is displayed in the message box.  Refer to your device manual for information on error messages.

Understanding Printer Responses

“Printer Responses” is defined as the feedback displayed by an application when making a request to a device that is in an error state.  This is a very complex issue as each device family may behave slightly differently.  The connection to the device further complicates matters.  This section provides information on what can be generally expected as responses back from devices in scenarios involving the different types of applications and device connections.

If you are driving the devices from your application using the Loftware Print Server, the only way to get positive (or negative) acknowledgement that your print request is successful is to use the TCP/IP interface to the LPS that is described in Chapter 1 of the LPS User’s Guide.

Serial
A serial connection is one that has been configured in Loftware Label Manager using a COM Port.  This is a two-way communication between the computer and the device providing more detail than other types of connections.  For example, if your printer is out of stock, you may get a specific error message similar to the following:

A “Recoverable Device Error” means that, when the error is corrected, the print job continues.  This is true for USB as well as Parallel printing.

Benefits of “Going Serial”

·      More detailed status information

·      Cable to printer can be much longer than a parallel cable (up to 50 feet).

Drawbacks

·      Requires a specifically “pinned” NULL/MODEM cable

·      Requires that printer settings for baud, stop bits, parity, data bits, and flow control match the same settings in the software.

·      Slower connection speed than the rest of the connection types.

·      The number of serial ports on a PC is limited to 1 or 2.

·      Loftware does not recommend serial connections when using the Loftware Print Server

Parallel
Stand-alone parallel printing involves a connection from a computers parallel port (LPT) to a Centronix (parallel) port on the printer.  Most new printers have a parallel port; many older or less expensive printers may not.  If the printer is in an error state, a message is displayed after an attempt to print the label.  With this type of connection, it may take from 1 second to 5 minutes to display the message depending on the type of error.  When no power is supplied to the printer, the error message is displayed instantaneously.

In other cases, such as the printer being in a “pause” or “stock/ribbon” fault mode, error messages may not be received until the printer’s memory buffer is full.  The amount of time this takes depends on the size of your label and how many requests that you have made.  When the fault condition is corrected, the labels print (as long as the printer has not been shut off).

Benefits of “Going Parallel”

·      No communications settings (baud, parity, etc) need to be set.

·      Parallel connections are 3 to 5 times faster than serial connections.

·      USB data transfer rate even faster, print quality high as well.

Drawbacks

·      Shorter cable lengths (15 feet max)

·      Status is not as detailed as a serial connection, but is considered “good enough.”

·      Computers usually only have one parallel port.

Spooling
Print Spooling uses the Windows Print Manager to queue requests to the device.  In stand-alone printing to a spooler, if the device is in an error state, an error message is displayed after an attempt to print the label.  When using a Generic Text Driver for example, if an error occurs, Windows displays information about the status of the device.  Many times, if the problem with the device is corrected and the Retry button is pressed, the label prints (assuming there are no other errors).

Benefits of Spooling

·      Requests are queued in the Windows Print Manager.

·      Devices that are connected to a PC on the network can be shared with other PC’s on the network.

·      Many devices (hundreds) can be set up on your network and made available for the Loftware Print Server or stand-alone applications.

Drawbacks

·      Can be very complicated to set up.

·      Increased CPU Utilization

USB
Universal Serial Bus (USB) is a protocol used for connecting computer peripherals to a PC.  USB provides an expandable, hot-pluggable Plug and Play serial interface that ensures a standard, low-cost connection for peripheral devices such as keyboards, mice, joysticks, printers, scanners, storage devices, modems, and video conferencing cameras. Migration to USB is recommended for all peripheral devices that use legacy ports such as the PS/2, serial, and parallel ports.  Up to 127 USB devices can be connected to one PC.  A main feature of the USB standard is that it allows many computer peripherals to be easily swapped for another without having to turn off the computer.  However, this is not recommended for configured Windows or Loftware USB printers because the printers are configured for the given Port assignment when the printer is connected to the USB Port.  USB 1.1 currently supports a data transfer rate of 12 megabits per second.

This high speed gives USB quite an edge over standard serial and parallel connections.  USB 2.0 supports even higher data transfer rates of up to 480 megabits per second for connection to high-performance peripherals.

Benefits of USB

·      High Data Transfer Rate

·      Longer Cables can be used, up to 30 feet

·      Up to 127 Ports may be utilized on one PC

·      Generally easier to connect, plug and play, little configuration, if any

Drawbacks of USB

·      Troubleshooting may be more difficult; behaviors under error conditions vary a great deal.

The USB 1.1 communication architecture connects a PC to a USB printer via a simple four-wire cable.  Many label printers are now available with USB port capability, and Loftware Applications now have the ability to print to these printers through their USB port.

TCP/IP
An IP connection involves configuring the LPS to print directly to the IP address of the device.  When an IP address in Stand-Alone Printing is used, error messages are displayed after an unsuccessful attempt to print the label. 

For example, if Loftware is connecting to a device that has an IP address but the device is not powered on, the connection fails and an error message is displayed.  In this scenario, when the device is powered back up, the label does not print; it has to be resent to the device, and is then printed.  (The Loftware Print Server recovers and prints the label in this case.)  In another scenario where the device is powered up but is in “pause” (stock/ribbon fault) mode, an error message is not created until the device’s memory is full, and then the error message is displayed.  When the fault condition is corrected, the labels that are in the device’s memory are printed, as long as the device was not shut off.

Benefits of using TCP/IP connections

·      Device can be anywhere LAN/WAN/Internet, etc.

·      Connection is fast and reliable.

·      Very easy to set up, as long as appropriate network hardware is in place.

·      Many devices (hundreds) can be set up on your network and made available for the Loftware Print Server or stand-alone applications.

Drawback

·      Device requires a network TCP/IP address that involves extra setup.  See your network administrator for more information on this.