Design Article
Replacing RS-232 with 802.11n wireless
N. Venkatesh, Redpine Signals
6/10/2009 1:44 PM EDT
The Wired Setup
The monitoring and control of medical equipment and devices are often carried out from a separate controller or server. The server may be in the vicinity of the equipment or may be at a remote location. Traditionally, a common means of connecting the two is via an RS-232 serial interface. Consider a set of sensors controlled by a sensor unit as shown in Figure 1. The accumulated data is transferred to a monitor via a serial interface.
Figure 1: Sensor Unit and Interface to Monitor
(Click on image to enlarge)
The multichannel A/D converter is typically within the microcontroller unit. The periodically sampled data is encapsulated in a predetermined packet format and sent on to the Monitor via the UART interface of the microcontroller.
The applications running on the microcontroller and the monitor (or server) ensure the means to transfer the sensor data meaningfully. The device application encapsulates the data using a protocol negotiated with the receiver of the data (the server in this case). The obtained data would be de-capsulated on the corresponding peer before passing it to the application. Figure 2 illustrates this process.
Figure 2: Wired Connection
(Click on image to enlarge)
There are many methods of encapsulation - one example for encapsulation of IP data is SLIP (Serial Line Internet Protocol). SLIP is a packet framing protocol that defines a sequence of characters that frame IP packets on a serial line. It provides no physical addressing or error control, for which it depends on upper-layer protocols. SLIP simply sends the data and then sends a signal marking the end of the data.
The monitoring and control of medical equipment and devices are often carried out from a separate controller or server. The server may be in the vicinity of the equipment or may be at a remote location. Traditionally, a common means of connecting the two is via an RS-232 serial interface. Consider a set of sensors controlled by a sensor unit as shown in Figure 1. The accumulated data is transferred to a monitor via a serial interface.
Figure 1: Sensor Unit and Interface to Monitor
(Click on image to enlarge)
The multichannel A/D converter is typically within the microcontroller unit. The periodically sampled data is encapsulated in a predetermined packet format and sent on to the Monitor via the UART interface of the microcontroller.
The applications running on the microcontroller and the monitor (or server) ensure the means to transfer the sensor data meaningfully. The device application encapsulates the data using a protocol negotiated with the receiver of the data (the server in this case). The obtained data would be de-capsulated on the corresponding peer before passing it to the application. Figure 2 illustrates this process.
Figure 2: Wired Connection
(Click on image to enlarge)
There are many methods of encapsulation - one example for encapsulation of IP data is SLIP (Serial Line Internet Protocol). SLIP is a packet framing protocol that defines a sequence of characters that frame IP packets on a serial line. It provides no physical addressing or error control, for which it depends on upper-layer protocols. SLIP simply sends the data and then sends a signal marking the end of the data.
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FlyByPC
6/23/2009 1:04 AM EDT
The drawback, of course, is cost. RS232 is a very simple, low-cost protocol, generally requiring a MAX202 and a few capacitors. 802.11b, let alone .n, is much more complex, since it requires support of the entire TCP/IP stack plus an encapsulation protocol. I'm sure it has its uses, but there are much better alternatives to replace RS232 over short distances.
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Oritek.Chawcs
4/19/2010 12:33 AM EDT
It look like this way. Computer this day dont even came with a serial port (RS232), mostly there is the USB port. You may get a USB to RS232 converter, but had to make sure that the software can support it, as this converter will not name as COM1 or COM3.
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Andrewier
4/19/2010 12:13 PM EDT
Is this an April's First joke article? To replace a simple and inexpensive (even accounting for all limitations) wired interface to a complex wireless protocol (and hardware)? Sorry, but it is nonsense. Of course it sometimes can be practical but never equivalent. For industrial control and other critical applications, RF could be impeded by interference creating unacceptable situations. Not mentioning cost, complexity at the controller's side and lack of determinism on packets.
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