TCA7408EVM Datasheet, PDF (4/14 Pages) Texas Instruments – Works with MSP430 Launchpad

Operation
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2.2 Hardware Setup
There are three different modes that the EVM can be used in, LED mode, Voltage reference mode, and
Variable gain mode. To setup any of these three modes, begin by connecting the EVM to the LaunchPad.
Note the location of the VCC and GND pins on headers J1 and J2 on both the LaunchPad and the EVM to
ensure correct installation.
Install a shorting jumper across pins 1 and 2 of J6. Connect an external +5V supply to J3 and either
connect the LaunchPad to a computer through USB or connect a 3.3V power supply to J6* on the
LaunchPad to power it up.
NOTE:
: It can be possible to power up the LEDs by connecting a wire from the VCC pin of J6 on
the LaunchPad to the positive pin of J3. A 5V supply might be required because the max
voltage drop across the blue LED plus the drop across the TLC59108 is larger than the
supply voltage of the LaunchPad.
3 Operation
The TCA5405 will control when D1-D5 light up. TPL0401B is connected in series to the REXT of the
TLC59108 LED driver this setup will control D6 and D7. Each color is set to a fixed PWM to ensure
baseline brightness is similar. Color mixing is then accomplished through unique methods. The desired
current is set by changing the W-L resistance of the TPL0401B and the desired LED is switched on. This
repeats for the other colors and then starts over. The LEDs are multiplexed at about 1000 Hz.
After setting up the EVM as described in section 2.3.1, LEDs D1-D5 should be blinking and D6 and D7 will
be blue. To increase the speed at which D1-D5 blink press SW1 and to decrease the speed press SW2.
There are 25 different colors that can be created with D6-7 starting with blue and ending with green. To
step through the colors from blue to green press S4. To step through the colors from green to blue press
S3.
4 MSP430 Code
4.1 TCA5405
Within the source code for the MSP430 there are two different methods to handle sending data to the
TCA5405. This section will explain how the TCA5405 functions and how the MSP430G2xx3 code works.
Figure 1. Data Flow for TCA5405
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TCA7408EVM,TCA5405EVM
Copyright © 2011, Texas Instruments Incorporated
SCPU034 – December 2011
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