AN2841 datasheet(21/31 Pages) STMICROELECTRONICS

部件名	AN2841

功能描述	This application note deals with the general principles of LED dimming

PDF	31 Pages

Scroll/Zoom	100%

制造商	STMICROELECTRONICS [STMicroelectronics]

网页	http://www.st.com

标志

21 / 31 page

AN2841

Dimming application using an STM32 microcontroller

21/31

Example of reduced lookup table generation

void performGenerateReducedLookUpTable(unsigned char *LEDmapIN,

int LEDcount, int PWMdepth, unsigned char **tableIN, unsigned

char **tableKeyIN, int *table_size){

int streamSize = LEDcount/8;

*table_size = differentValuesCount(LEDmapIN, LEDcount);

*tableKeyIN = SortAndReduce(LEDmapIN, LEDcount, *table_size);

*tableIN = malloc(streamSize * (*table_size)

* sizeof(unsigned char));

for(tmpdepth = 0; tmpdepth < (*table_size); tmpdepth++){

for(DATAchar = 0; DATAchar < streamSize; DATAchar++){

for(outputBIT = 0; outputBIT < 8; outputBIT++){

(*tableIN)[tmpdepth*streamSize + DATAchar] <<= 1;

if(LEDmapIN[(DATAchar*8) + outputBIT] >

(*tableKeyIN)[tmpdepth])

(*tableIN)[tmpdepth*streamSize + DATAchar] |= 0x01;

else

(*tableIN)[tmpdepth*streamSize + DATAchar] &= 0xFE;

}

Table 3.

LEDmap - requested LED brightness configuration

Outputs

LED 1

LED 2

LED 3

…

LED i

Duty cycle (brightness)

2 / 2n

6 / 2n

4 / 2n

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