EVM Description
The two files provided, LP8557.exe and USB2ANY.dll, must be unzipped to a directory together. This
program is Windows7-compatible. (For running on Windows XP a Microsoft installation file is required.)
The USB2ANY is recognized as an HID-compliant device in Windows Device Manager. Successful
communication with the board by the application is confirmed by the "Version: " field at the bottom of the
application showing the correct USB firmware revision. The I
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C-compatible device address is fixed at 0x26
in this program. The sections on the left side are used to update the registers of the device. The columns
of registers on the right are updated by clicking the "Readback All" button. An update to the registers on
the left does not automatically reflect in the readback registers. Just click the "Readback All" button to
check the results of the actions. The register addresses are shown with the register names in the boxes
surrounding the controls. The minimum procedure for turning on the LEDs is as follows:
1. Connect the LED board to the LP8557 evaluation board. Set jumpers for number of LEDs per string.
2. Connect external power and ground to the board.
•
Suggest 3.6V to VIN jack
•
Suggest 3.6V to VDD jack. (Alternatively install jumper P2 to connect VDD to VIN.)
•
Connect Ground to GND jack.
3. Turn on the external supplies.
4. Connect USB2ANY to computer USB port.
5. Run LP8557.exe
6. Change the Mode in the dropdown box under "Config Register" to "Brightness Hi/Lo register only".
7. Check the "Enable Backlight" box.
8. Move the slider under "Brightness Addr 03 and 04" to increase the current provided to the LEDs.
The 02 Status Register will update every time the "Readback All" button is pressed. The status register
should show "VRef OK" and "VBoost OK" checked indicating normal operation after the steps listed
above are performed and the "Readback All" button is pressed. Access to any register is available
through the "Manual Control" on the lower right. See the LP8557 datasheet (
) for detailed
descriptions of the registers and their usage. NOTE: Do not change the configuration of the device
while the backlight is enabled. First disable the backlight by making sure "Enable Backlight" is
unchecked. Then adjust the configuration and turn on the backlight. Changing the configuration while
the backlight is on may produce unexpected results.
NOTE: If the part is enabled to any level of brightness or state and the program is closed, the LP8557
device will remain in the last controlled state.
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EVM Description
The LP8557IEVM kit includes the main evaluation board, an LED loadboard, and the USB2ANY interface.
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LP8557IEVM User Guide
SNVU371 – December 2013
Copyright © 2013, Texas Instruments Incorporated