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envision. We use
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send the text that I loaded in Screenshot 2. Technically,
I have less than one second after pulling the ground
connection to get the ASCII text to the RFD21733.
I pulled off the manual ESN read-back procedure
successfully. Screenshot 3 verifies that the transmitted
ESN packet bytes in Screenshot 1 match up with the ESN
data we obtained with the ESN read-back procedure.
Adding a Microcontroller
The evaluation board contains combinatorial logic that
is used to buffer the LEDs and provide some mode switch
logic. You can download a complete schematic diagram
from the RF Digital website (see Sources).
Once you get your copy of the schematic, you’ll notice
that most of the RFD21733’s I/O and control pins are
pulled down with 47KW resistors. The only exceptions are
the RFD21733’s RESET pin — which is pulled logically high
internally — and the mode input MO — which is internally
pulled logically low.
Note also that all of the I/O and control pins are
electrically connected in series with a 220W resistor. The
47KW and 220W resistors should also be included in your
microcontroller-supported RFD21733 design. As it stands,
you can simply connect a microcontroller’s I/O directly to
the evaluation board’s 12-pin header. Only eight I/O lines
are required, so the remaining I/O lines of the PIC can be
used to interface to other stuff like motor drivers and
A Robot’s Radio
What more could a robot want? The tiny RFD21733
can stand alone powered only by a coin cell. It’s just as
much at home when dangling from the UART of a PIC.
With built-in 16-bit CRC, motor noise tolerance, and
networking capability, the RFD21733 is truly a robot’s
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