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Changing Brightness Control from I
2
C/SPI Register Control to PWM Input Pin Control
51
SNVU382A – April 2014 – Revised June 2014
Copyright © 2014, Texas Instruments Incorporated
Quick Start Guide
D.5
Changing Brightness Control from I
2
C/SPI Register Control to PWM Input Pin Control
By default (default EEPROM setting of the LP8860-Q1 on the EVM) LED brightness is controlled through
the I
2
C/SPI registers.
It is also possible to use an external PWM input signal to control LED brightness. On the EVM PWM
signal is generated by MSP430 so that the user does not need to bring external signal for the first testing.
To use PWM input pin for brightness control EEPROM setting needs to be modified using the following
procedure:
1. Make sure LED brightness is 0%. Also check that PLL is disabled in
LED drivers
tab.
2. In
LED drivers
tab for
Display brightness mode
select
PWM input pin duty cycle control
.
3. If the user wants to save new setting in EEPROM,
Burn EEPROM
is selected. After EEPROM burning
toggle VDDIO/EN, the device resets.
4. In
Pin control
tab:
a. Enable PWM generator (on MSP430, generating PWM input for the LP8860-Q1).
b. Set PWM input duty cycle
Duty, %
, press
Update
to activate PWM. Another option is to use
sliding control. LEDs will turn light on.