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  • LED Dimmer Demoboard

  • Created: Jun 24, 2014

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LED Dimmer Demo Board

This schematic demonstrates the capability of the I2C-bus to control a keypad and perform Red/Green/Blue (RGB) LED-lighting color mixing operations. Two sub-boards that are directly connected to each other without the need for external cables compose the demo board: the Keypad Control Card and the LED Control Card. The cards can be used separately and can be connected to other cards. The colors red, green, and blue are the three primary colors that are used to create other colors by mixing them together. A desired color can be obtained by mixing the right amount of red, green, and blue lights from the RGB LED.

The schematic takes advantage of the Philips P89LV51RD2 microcontroller and the Philips PCA9564 I2C-bus controller to generate the different I2C commands. The firmware in the P89LV51RD2 microcontroller emulates a cell phone application, programs fun patterns, and controls the brightness of a virtual display. Battery discharge emulation with a visual charge status can also be performed. The firmware is intended to show a specific application (i.e., cell phone), but this demo board can be used for any application that requires a keypad control and LED lighting or color mixing. The default firmware in the P89LV51RD2 allows the user to control the 16-key keypad, control the RGB LEDS and display speed, control brightness of the white LEDs, emulate a “battery discharge” application, and enable an “Auto Demo Mode.”

Keypad control is done using a PCA9555 with its INT signal connected to a GPIO of the P89LV51RD2 microcontroller. The sixteen keys of the keypad are simply connected to the sixteen GPIOs of the PCA9555 and to the ground, without any other external components since internal 100kΩ pull-ups are provided by the PCA9555.



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