old-fashioned way, we will have to interface our PW1-928
via one of the Dell’s many USB ports.
To do this, we will deploy an FTDI TTL to RS-232
converter cable between the PW1-928 and the computer.
The FTDI cable electrical pinout scheme is displayed in
Figure 4. This particular cable is terminated on one end
with a USB connector. The opposite end is exposed as a
six-pin 0.1 inch pitch female connector. You can obtain
this cable from Digi-Key or Mouser.
The PW1-928’s serial_in signal is connected to the
FTDI cable’s TXD pin. The FTDI cable’s RXD signal is
connected to the PW1-928’s serial_out pin. We must also
place a jumper on the dev kit’s JP5, which will take the
PW1-928 out of standby mode. The PW1-928 dev kit will
be powered by a standard nine volt battery.
According to the PW1-928 datasheet, if we send the
PW1-928 a pair of ASCII exclamation points (!!) at 2400
bps, it will return an ASCII greater-than symbol (>).
All of the PW1-928 programming command
strings must be prefixed with two exclamation mark
characters (ASCII 0x21) and are terminated with a
carriage return (0x0D). All command string alpha
characters must be in upper case, and command
string numeric data must be in hexadecimal format.
Spaces are ignored and can be added for enhanced
human readability. The ESC character terminates
and cancels any command entry.
The complete list of PW1-928 commands can
be found in Figure 5. The terminal emulator I am
using is called the Serial Input/Output Monitor and
comes as part of the CCS PIC C compiler package.
As you can see in Screenshot 1, I’ve used the
terminal emulator’s macro feature to code up some
of the PW1-928 command structures. What you see
in Screenshot 2 are the results of the execution of
the edumpSerialNum macro.
Pushing the PW1-928’s Buttons
The dev kit comes with a pair of PW1-928
carrier boards. We can easily put the PW1-928
radio modules to work without writing a single line
of code or issuing a single command. The PW1-928
can be forced into test mode by simply placing
58 April 2017
■ SCREENSHOT 1. Yep. Two ASCII exclamation points (!!) will
spawn a greater-than symbol (>) answer from the PW1-928 RF
data transceiver module.
■ FIGURE 5. These are the PW1-928 commands. Be sure to
enter the EDUMP numeric in ASCII format. For instance, the
EDUMP0 command equates to 21214544554D50300D.
■ SCREENSHOT 2. I used the macro capability of the
CCS C Compiler’s serial I/O app that comes
packaged with their compiler to issue the read serial