AN2841 datasheet(29/31 Pages) STMICROELECTRONICS

Numer części	AN2841

Szczegółowy opis	This application note deals with the general principles of LED dimming

PDF	31 Pages

Scroll/Zoom	100%

Producent	STMICROELECTRONICS [STMicroelectronics]

Strona internetowa	http://www.st.com

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29 / 31 page

AN2841

Achieved values

29/31

Table 12 and Table 13 show the results in case you remove the additional LE edge used for

the measurement of the interrupt end and optimize time between two interrupts (used for

SPI in 16-bit mode).

4.1

Dimming approach comparison and conclusion

4.1.1

Comparison between interrupt and interrupt + DMA approaches

When using the single interrupt approach described in Figure 12 and Figure 13, the time

spent by the MCU to drive the LEDs is long and little time is left to execute other tasks.

The combination of the single interrupt + DMA approach frees more computing time for

other tasks. This approach does not improve the refresh rate.

4.1.2

Comparison between dynamic preparation, static, and reduced static

lookup table

The dynamic data preparation shown in Figure 9 allows to save memory but requires

additional computing time.

The static lookup table method saves computing time. However, the computing must be

performed at the beginning of the dimming.

The reduced static lookup table offers the same functionalities as a full lookup table, while

saving memory space.

AN2841 Arkusz danych(PDF) 29 Page - STMicroelectronics