National Instruments NI myRIO, Essentials Manual

Page: 76 / 163

70 CHAPTER 9. POS TERMINAL
Digilent PmodCLS LCD Display
Chapters 26 to 28 of the NI myRIO Project Essentials Guide
2
provide a detailed
explanation of the Digilent PmodCLS LCD display using its UART, SPI, or I
2
C-
bus interface as well as LabVIEW demonstration code available at NI myRIO
Project Essentials Guide .zip Files
3
that you can drop into this project. Study
LCD Character Display Interfacing Theory
4
to learn how to write escape se-
quences to configure and control the LCD display and then study one of these
block diagram “walk-through” videos depending on the serial bus that you wish
to use:
LCD (UART) Demo Walk-Through
5
, LCD (SPI) Demo Walk-Through
6
,
or LCD (I2C) Demo Walk-Through
7
.
T
IP
: Refer to the NI myRIO connector diagrams in Appendix B on
page 137.
LabVIEW Techniques
Some tasks should execute only one time after a Boolean flag sets. For example,
the
barcode in view
flag is clear when no valid barcode is visible and is set
the entire time a valid barcode is visible. However, the
update shopping
cart
task should execute one time only when the
barcode in view
flag
first changes from clear to set. Study Create “Flag Change” SubVI
8
to learn how
to create a subVI that detects when a flag changes state.
Use the Search 1D Array function to look up an item code in the inventory
“item codes” array. This function returns the index of the matching element or
−
1 when no match is found. This index may then be used for the Index Array
function.
Use the IMAQ Overlay Multiple Lines 2 VI to create the barcode bounding
box from the “Bounding Box” element of the barcode
Data
custom control. As
of this writing the VI throws an error that states that the bounding box does not
contain enough points. However, simply disconnect its error cluster output and
you should find that the overlay works properly anyways. Experiment with the
Width
and
Color
inputs to produce a satisfactory bounding box.
2
http://www.ni.com/myrio/project-guide
3
http://www.ni.com/academic/myrio/project-guide-vis.zip
4
http://youtu.be/m0Td7KbhvdI
(10:36)
5
http://youtu.be/JsEMMnIWg4k
(3:44)
6
http://youtu.be/oOXYryu4Y-c
(4:23)
7
http://youtu.be/qbD31AeqOMk
(4:32)
8
http://youtu.be/N1hUkWeZ8x0
(6:58)