AN4460 datasheet(31/54 Pages) STMICROELECTRONICS

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AN4460

User interface

7.4.2

ll - change LED dimming level

To change the LED dimming level, use the “ll” command. The value is stored into the

E2PROM data area for its read back and applies to next power-on.

Syntax: ll [ch] [level]

Parameters:



ch [0-3]: the LED string channel value.



level: [0-256]: indicates the dimming level in a scale from 0 (OFF) to 256 (always ON),

a value between 1 (0.4%) and 255 (99.6%) indicates the dimming level. A value of 256

turns the LED chain on at full brightness (100%). When the global dimming level is

different from 100% (via “ed” and “di” command), the equivalent current on example is

equal to ('level / 256) * (global dimming level).

Output: none

Example: “ll 3 200": sets up channel 3 to use a current equal to 200/256 of the maximum

current defined by the “lc” command.

7.4.3

ln - configure LED number

Used to setup, before connecting any LED, the number of LEDs used in a specified chain.

The value is stored into the E2PROM data area for its read back and applies to next power-

on.

Syntax: ln [ch] [num]

Parameters:



ch [0-3]: the channel number.



num [3-10] the number of LEDs. The minimum LED number is 3; the maximum LED

number is 10.

Output: none

Example: “ln 1 6": sets up six LEDs on the channel 1.

7.4.4

ad - read ADC channel

Reads the ADC channel [ch] and displays the result in decimal value.

Syntax: ad [ch]

Parameters:



ch [0-7]: ADC channel number. For the ADC channel association, see the board

schematics.

Output:



The output value is the decimal conversion read from the ADC channel. The value read

from the LED channel (VCOMx point) depends on the dimming level. The correct input

voltage at the STLUX385A pin is given by the ADC value multiplied by 0,001221896

{= (1.25/[(210)-1]}. For channels 0, 1, 2, 3, 4, 6, the ADC value has to be multiplied for

0.05437489.

Example: “ad 0": reads the power line voltage.

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