The Narrow band Evaluation Kit (NBEK) IC can be used as 1200baud half-duplex serial modem suitable for narrow band receivers, transmitters and transceivers (or any RF modules with >5kbps data rate). It takes care of preamble, synchronisation, bit balancing and error checking and enables a transparent radio data link to be established between radio devices. This is a half duplex unit, so collisions between transmitted and received packets must be dealt with by the user. Provided no two devices attempt to transmit simultaneously no further restrictions on data transmission need be made, as all transmit timing, valid data identification and data stream buffering is conducted by the unit. Synchronisation and framing words in the packet prevent the receiver outputting garbage in the absence of wanted RF signal or presence of interference. Supports 1200 baud asynchronous data: 1 start bit, 8 data bits, 1 stop bit.
With typical microcontrollers and UARTs, direct connection is usable as shown on figures 2 & 3. To connect to a true RS232 device, inverting level shifters must be used (MAX232 type are ideal, but simple NPN/PNP transistor switches often suffice as used in the application circuits figures 4 & 5).
