Input/Output Port Hardware Considerations for a Thin Client (Windows Embedded CE 6.0)

1/5/2010

This topic discusses considerations for I/O port hardware for a Windows Embedded CE powered thin client.

I/O Port Requirements

Although parallel and serial ports are not required, we recommend them. Remote Desktop Protocol (RDP) supports serial port and parallel port redirection. Therefore, a server application can interact with an I/O port on a thin client to connect to remote peripheral devices, such as a bar code scanner.

To enable port redirection during a Terminal Services session, include the Serial and Parallel Port Redirection Catalog item (SYSGEN_RDP_PORT) in your OS design. When you add SYSGEN_RDP_PORT to an OS design, it automatically includes both Parallel Port Support (SYSGEN_PARALLEL) and Serial Port Support (SYSGEN_SERDEV) Catalog items.

Notice that that only serial ports and parallel ports support port redirection.

Serial Ports

A serial port, also known as a COM port, includes the internal hardware component, based on the RS-232-C standard, and the external DB-9 connector that accepts connections from a serial cable.

Your thin client can include one or several serial ports. The following table shows the requirements for a serial port on a thin client device.

Requirement	Description
The port must meet minimum RS-232-C hardware requirements, if RS-232 is present.	Generally, the serial port hardware must support the standard technologies found in the universal asynchronous receiver/transmitter port of a computer.

The following table shows the recommendations for a serial port on a thin client device.

Note

You should select hardware that meets the needs of the peripheral devices that will connect to the serial port. You can obtain a USB to Serial converter to support connections to USB devices through serial ports. With a converter, you can redirect USB peripheral devices that connect to a serial port.

Recommendation	Description
The port should support minimum speed requirements.	The port should support speeds from 38.4 kilobauds per second up to, and including, 115.2 kilobauds per second.
The port should meet framing requirements.	The port should support all the combinations of parity and stop bits. In addition, it must support word lengths of at least eight data bits.
The port should meet flow-control requirements.	The following list shows the support recommendations for hardware flow control: Request To Send (RTS): required Clear To Send (CTS): required Data Terminal Ready (DTR): optional Data Set Ready (DSR): optional. The port should support software flow control. This includes supporting a clean stop in the current buffer transmission. The serial port should also support a maximum skid of 16 bytes. This value is the maximum number of bytes that continue to be sent after the receiver requests a flow control off command.
The port should support a break in hardware.	When the serial port hardware receives a break command, it should stop transmission cleanly at a framed byte boundary. Notice that receiving the break command differs from reading a continuous stream of 0 bytes, because the 0 bytes are framed data.
The port should use a standard DB-9 connection.	For ease of use and convenience, serial ports should use the standard DB-9 connector.

For more information about serial ports, see Programming Serial Connections.

Parallel Ports

A parallel port is a bi-directional port based on the Centronics parallel interface with the improved scalable parallel processing (SPP) mode, also known as bi-directional SPP mode. Parallel ports are for printing, not for general data transfer. They use the IEEE 1284 compatibility mode in the forward direction, and nibble mode in the reverse direction.

The following table shows the parallel port requirements on a thin client device.

Requirement	Description
The port must be compliant with the IEEE 1284 interface specification	The port hardware must meet the industry standard specification for parallel port communications.

For more information about parallel ports, see Parallel Port Architecture.

See Also

Concepts

Performance Considerations for the Hardware Components of a Thin Client
User Input/Output Hardware Considerations for a Thin Client
Hardware Architecture Diagram for a Thin Client
USB Host Controller Hardware Considerations for a Thin Client