OPERATION GUIDE
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OG_CDP-RX-07M_v20e Circuit Design, Inc.
7
OPERATING INSTRUCTIONS
Supply voltage
The CDP-RX-07M contains a voltage regulator to guarantee stable performance in the given range of supply
voltage. It is designed to operate on batteries and operates with low voltage and low current consumption. The
supply voltage must be within the specified voltage range. The module shows an unstable operation with the
lower voltage specified.
If there is a lot of power supply noise, or if there is a noise source nearby, receiver performance such as
sensitivity may be degraded.
Data format
The maximum data rate is 4800 bps. The maximum pulse width for continuous High and Low signal is 20 ms
(96 bits) at 4800 bps. The minimum pulse width is 208 us.
Long intervals of HIGH or LOW bits should be avoided. Succeeding bits can be distorted in their pulse width. If
the sequence of HIGH or LOW bits is too long then there is a possibility that the logic level of the data output
will change.
It is good to have a 20bit preamble (1010…) in front of the data to ensure communication reliability.
Inputs/Outputs
The CDP-RX-07M has 3 output terminals (AF, DATA and RSSI) and one input terminal (CTRL).
The AF output is the analog output from the FM detector circuit.
The DATA output is a digital output. This is the signal after AF signals pass through a band pass filter and
comparator. The output signal level is 0 to Vcc and can be easily connected to other digital circuits.
The RSSI output is an indicator of the received signal strength. The stronger the received signal is, the higher
voltage is output. There is individual variability in the output level of the RSSI signal. Also it should be noted that
the output voltage may be reduced depending on the load impedance to be connected.
The CDP-RX-07M does not have a built-in mute circuit. The AF and DATA outputs will show noise on the
outputs when no signal is received. Valid data signals can be detected by utilizing the RSSI output to configure
a mute circuit.
The CTRL input can be used to control the internal voltage regulator and turn on/off the power supply to the
internal circuit. Normally, use this terminal as Open or Gnd-short.
Antennas
Connect an antenna of 50 Ω impedance according to the frequency to be used. Note that the performance of
the antenna changes significantly depending on the connection condition, shape, and surrounding environment,
and it affects the reception sensitivity and distance.
