RF Modems
JCX will include RF data modems which support the JXTA protocols and provide a peer-to-peer ad-hoc network ideal for small robots. A PC or other TCP/IP capable system such as JStik can act as a TCP/IP to JCX gateway, as can a PC. The RF Modem boards can be used in a JSimm backplane in robots or industrial equipment, interfaced to a controller such as JStamp or JStik or TStik. You can also plug the RF Modem board into a PC serial port via a DB9 connector. This enables PDAs or notebook PCs to participate in a control network, or (if the PC has ethernet access) to act as an RF-to-TCP/IP gateway.

More RFModem technical data
How RFModems workThe "big picture" of how this sort of communication works
RFModem progress report log Detailed progress reports, technical decisions and history of the RF Modem project
RFModem JXTA projectWeb area related specifically to JXTA support for the RF Modems

RF Modem architecture
Here's a photo of the long range 916 MHz modem mounted on its JSimm carrier board. We have a handful of these prototypes up and working and are in the process of adding JXTA support. The wire antenna can be seen just leaving the upper right corner of the board (it's a flexible white wire). The 2.4 GHz modems use a different antenna style.
Frequency916 MHz (USA) and 2.4 GHz (Europe)
RangeLong range models - over 1 Km unobstructed line of sight. Short range models - 100-200 meters
FCC CertificationYes, FCC and european agency approved
Data rateLong range: 19200 baud (net). Short range: 38400 baud (net)
Application layer protocolsJXTA (http://www.jxta.org) JXTA technology is a set of open protocols that allow any connected device on the network ranging from cell phones and wireless PDAs to PCs and servers to communicate and collaborate in a P2P manner. JXTA peers create a virtual network where any peer can interact with other peers and resources directly even when some of the peers and resources are behind firewalls and NATs or are on different network transports.
Hardware interfaces

JSimm/SimmStick bus with TTL-level serial I/O when used with a JSimm or SimmStick controller. JStamp or JStik communicate with the RFModem in this manner. TStik can too, using the new TILT400 socket board. An adapter is available with RS232 level shifters and a DB9F wired as DCE. The RFModem board can therfore be used with any computer which has an RS232 serial port. An SPI interface drives the control signals for the modem and accesses tagging memory. We're not sure how this will work with the generic RS232 interface (which won't have SPI access).

Host Controller compatibilityJStamp, JStik, and TStik (with TILT400), or any JSimm- or SimmStick- compatible controller with asynchronous serial TTL interface per the JSimm pinout, and a SPI interface to access the modem control bits. Our implementation of JXTA will be only in Java, but there are C-language JXTA initiatives underway (we don't plan to participate in these, but you could). Also any Java-capable device with an RS232 port and our JSimm/RS232 adapter board.
Signal Strength monitorYes, built in.
Tagging memoryYes, via SPI interface, compatible with JCX hardware and software. We're not sure how this will work with the generic RS232 interface (which won't have SPI access).
Power consumption (transmitting)5 VDC 150 mA for long range models, 5 VDC 50 mA for short range models.
Form FactorJSimm board 3.5 x 2.5 x 0.5 inches. Antenna is a flexible wire whip four inches tall. Other higher efficiency or directional antennas are optional

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