Texas Instruments LP8580EVM, User Manual

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Examples
17 SNVU495 – March 2016
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Copyright © 2016, Texas Instruments Incorporated
LP8580 Evaluation Board
Figure 15. Operation Menu
6 Examples
This section describes how to do some basic operations with the LP8580 evaluation software. Note that
the EEPROM settings affect how the LP8580 starts up; some of the following steps can be skipped if
correct settings are already set in the EEPROM.
6.1 Starting up the LP8580EVM
To start up the LP8580 and to communicate with the device, follow these steps:
1. Connect and set up the EVM hardware as described in Section 3 , and turn on the power supplies.
Either an I2C or SPI interface can be selected as described in Section 3.5 and Section 5.2 .
2. Set the EN pin high by setting Enable button to ON state.
3. Select Operation → Read All Registers . All register values should now be available on the register
view.
NOTE: The LP8580 EEPROM has an AUTOSTART bit. If AUTOSTART bit is set to 1, the I2C and
SPI interfaces are available once VDD voltage is applied, even if the EN pin is low.
6.2 Turn Backlight ON and Control the Brightness
This example assumes that AUTOSTART bit is set to 0.
1. Start up the device as described in Section 6.1 .
2. Set the desired LED output current into the LEDx_CURRENT registers. These registers can be found
under the Backlight_settings memory block.
3. Set the desired PWM value for each LED output into the LEDx_B0 registers. These registers can be
found under the Backlight_settings register block.
4. Write 0x0001 into register BRT_DB_CONTROL register under the Backlight_settings register block.
This simultaneously latches the regional PWM values to the LED outputs.
5. Write 0x0586 into BL_MODE register under the Configuration memory block. This enables the
backlight and sets the brightness control to register control. More information about the different
brightness control methods can be found in the LP8580 data sheet (
SNVSA65 ).
6. The brightness of the whole backlight can now be controlled with the BASE_BRT register. Brightness
of the individual LED strings can be controlled with the LEDx_B0 registers. After changing the
LEDx_B0 registers, 0x0001 must be written to the BRT_DB_CONTROL register before the change
takes effect.
6.3 Using PWM Brightness Control
This example requires that the I2C interface is selected, and the backlight is turned ON, as described in
Section 6.2 :