Pololu Wixel - Manual (Page 52)

Connecting the Wixel to the ShiftBrite chain
The following connections should be made between the Wixel running the ShiftBrite App and the first ShiftBrite in
the chain:
Wixel ShiftBrite Function
P1_4 EI Enable
P1_5 CI Clock
P1_6 DI Data
P1_7 LI Latch
GND GND Ground
Additionally, the Wixel and ShiftBrites may share the same VIN as long as the voltage requirements for both modules
are satisfied. For initial testing, you may alternatively use VALT to power the ShiftBrites from USB (see
Section 5.a ).
Using the ShiftBrite App
After making the correct connections and applying power, open a terminal program and connect to the COM port
created by the Wixel running the Wireless Serial App. Type
ffffff
. As you type the characters, they will be echoed
back to your terminal. Press Enter, and the first ShiftBrite in your chain will light up in white. Then type
ff0000
and
press Enter; now the first ShiftBrite should be red, and the second should be white (if present).
To shift out multiple color commands at once, for example when you want to set the colors of the entire chain, type a
series of single-color commands without pressing Enter, then press Enter once to apply them all.
Parameters
• radio_channel: The channel number is from 0 to 255 and determines which frequency to broadcast on. The
default is 128. Wixels must be on the same channel to communicate with each other. To avoid interference,
Wixels that aren’t supposed to talk to each other should be at least 2 channels away from each other. For example,
you could have one pair of Wixels on channel 128 and another pair on 130.
• input_bits: The number of bits per channel that you would like to use to send color information. The allowed
values are 1 to 16, and the default is 8, which corresponds to colors represented by 6-digit hex values. However,
the ShiftBrite supports 10 bits of resolution, so choose a value of 10 to make use of its full dynamic range. In this
case, you must send 9 digits to set a color. For example,
3ff3ff3ff
is the brightest possible white and
001000000
is the dimmest possible red. Other values for this parameter might be useful in special situations (e.g. 4 bits of
resolution lets you specify a full color in three bytes, such as
f00 for red, which allows for a higher update rate).
• echo_on: Set to 0 to disable echoing of every character sent. While echoes are useful for debugging, you
might want to disable them for the highest possible speed.
Data Format
The data consists of a series of red, green, and blue (RGB) values, as ASCII hex strings. Each value contains from 1
to 4 characters, depending on the value of input_bits, specifying a number from 0 to 2
input_bits
-1. When a complete
set of R, G, and B values has been received, the values are multiplied or divided by the appropriate factor to match
the 10-bit ShiftBrite data format and shifted out to the ShiftBrite chain. An Enter character (ASCII 10 or 13) causes
the Latch pin to be toggled, instantly setting each ShiftBrite to its new color.
Pololu Wixel User's Guide © 2001–2014 Pololu Corporation
9. Wixel Apps Page 52 of 64