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LP55231: What are the I2C instructions to light an LED?

Siddharth Chinoy
Prodigy 10 points
Other Parts Discussed in Thread: LP55231

I am able to read and write the configuration registers on the LP55231 over I2C, using an Atmega microcontroller.


After going through the datasheet, it is not clear to me what sequence of instructions is required to light up the LEDs.

Can anyone who has successfully used this IC tell me the sequence of reads/writes that should be performed?

(I have tried setting CHIP_EN to 1, and then setting OUTPUT ON/OFF CONTROL (reg 0x05) to hih for the corresponding LEDs. however, no success)

  • 0
    TI__Intellectual 1985 points

    After you enable the device via register 0x00, you also need to select the clock source and set the charge pump to 1X, 1.5X or Auto via register 0x36. You can then decide which LED you are going to turn on by programming the corresponding PWM.

    The brightness of the LED is a function of the PWM (reg 0x16 for D1) and the current control ( reg 0x26 for D1). For example, if you want to turn on LED connected to pin D1, you will need to program register 0x16 to a value that correspond to the brightness. By default the current limit for D1 is 17.5mA, you can also change this via reg 0x26.

    Below is a simple sequence to power up LED for a 50% brightness on D1 base on our EVM using i2c address 0x32

    Write 32 00 - 40
    Write 32 36 - 43
    Write 32 36 - 5B
    Write 32 16 - 80

    If the LED is still not ON, check the voltage at VOUT, if it is 1X or 1.5X of Vin, then the program is correct, you might want to check your LED or other related hardware.

    Regards
    H L