CIRCUIT DESIGN, INC
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CDP-02N UHF Synthesized Radio Data Module Operation Guide
7
Data format:
The digital data fed to the transmitter is passed through an internal low-pass filter to limit the
bandwidth of the digital data. This is needed for an efficient use of the available RF spectrum.
At the receiver, a band-pass filter is used to recover the data signal from noise. Together the
transmittable signal bandwidth is approximately 150 Hz to 2400 Hz. At the receiver, the signal
is converted back into a digital signal for compatibility with succeeding digital systems. The
type of digital data signals transmittable is limited by the bandwidth of the system.
DC signal or long intervals of HIGH or LOW bits should be avoided. Succeeding bits can be
distorted in their bit length. If the sequence of HIGH or LOW bits is too long it is possible that
the logic level of the data output will be changed.
The best countermeasure is to use a digital encoding scheme, which guarantees that no low
frequency components are included in the data signal. This can be achieved, for example, with
the "Manchester" encoding. A digital 1 is coded in a sequence of 10 and a digital 0 is encoded
into a sequence of 01. In most cases it is also sufficient to transmit serial data by using start
and stop bits of different logical level as can be done with the RS232 format. Each transmitted
byte will be preceded by a 0 bit and succeeded by a 1 bit.
The CDP-02N was tested with a number of standard encoder-decoder IC's for simple remote
controls. For data speeds in the 300 to 4800 Baud range no trouble should occur.
Because of the wide variety of data formats, data speeds and digital modulations techniques, it
is best to set-up a 'worst case' scenario and test the data transmission before the CDP-02N is
used in a practical application.
Further advice can be given if the precise format of the data and system requirement is
notified to the dealer or directly to Circuit Design, Inc. Your inquiries and comments are
welcome and will also help other users.
Channel and Frequency Setting:
EU Type
By use of chip mounted 4 bits switch and a jumper on the PCB, 32 channels can be easily
selected.
The 32 channels are divided to 2 groups: group A and group B. Each group of channel can be
selected by solder the jumper ON or OFF. The jumper ON is the state of group A. The jumper
OFF is the state of group B. There are 16 channels in each group and can be selected by the 4
bits switch easily.
Before shipment all the modules are set to the group B and all the 4 bits of switch are set to
the state of OFF. (434.65 MHz)
UK Type
All the 11 channels can be easily selected by the 4 bits switch on PCB. Please refer to the
CHANNEL AND FREQUENCY SETTING for channel selection.
