The device for Mediatek MT6370 RGB LED

Description

The MT6370 integrates a four-channel RGB LED driver, designed to provide a variety of lighting effect for mobile device applications. The RGB LED devices includes a smart LED string controller and it can drive 3 channels of LEDs with a sink current up to 24mA and a CHG_VIN power good indicator LED with sink current up to 6mA. It provides three operation modes for RGB LEDs: PWM Dimming mode, breath pattern mode, and constant current mode. The device can increase or decrease the brightness of the RGB LED via an I2C interface.

The breath pattern for a channel can be programmed using the “pattern” trigger, using the hw_pattern attribute.

/sys/class/leds/<led>/hw_pattern

Specify a hardware breath pattern for a MT6370 RGB LED.

The breath pattern is a series of timing pairs, with the hold-time expressed in milliseconds. And the brightness is controlled by ‘/sys/class/leds/<led>/brightness’. The pattern doesn’t include the brightness setting. Hardware pattern only controls the timing for each pattern stage depending on the current brightness setting.

Pattern diagram:

     "0 Tr1 0 Tr2 0 Tf1 0 Tf2 0 Ton 0 Toff" --> '0' for dummy brightness code

      ^
      |           ============
      |          /            \                                /
Icurr |         /              \                              /
      |        /                \                            /
      |       /                  \                          /   .....repeat
      |      /                    \                        /
      |   ---                      ---                  ---
      |---                            ---            ---
      +----------------------------------============------------> Time
      < Tr1><Tr2><   Ton    ><Tf1><Tf2 ><  Toff    >< Tr1><Tr2>

Timing description:

  • Tr1: First rising time for 0% - 30% load.

  • Tr2: Second rising time for 31% - 100% load.

  • Ton: On time for 100% load.

  • Tf1: First falling time for 100% - 31% load.

  • Tf2: Second falling time for 30% to 0% load.

  • Toff: Off time for 0% load.

  • Tr1/Tr2/Tf1/Tf2/Ton: 125ms to 3125ms, 200ms per step.

  • Toff: 250ms to 6250ms, 400ms per step.

Pattern example:

"0 125 0 125 0 125 0 125 0 625 0 1050"

This Will configure Tr1/Tr2/Tf1/Tf2 to 125m, Ton to 625ms, and Toff to 1050ms.