AN2841

Dimming application using an STM32 microcontroller

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Once the brightness data is determined, the repetitive dimming procedure needs only to

take the prepared data and send it to the LED driver.

Figure 11 shows the calculation time of the algorithm.

Figure 11.

Static lookup table time consumption with 166 kHz - 333 kHz LE signal

Accurate LE timing and the dimming part running in the application background are

necessary requirements for a successful application. These targets can be achieved using

the following methods:

●

Single interrupt

●

Single interrupt with DMA

●

Interrupt + DMA + interrupt

3.1.3

Single interrupt

The simplest approach is to use a timer interrupt approach where only a timer interrupt is

required for the data transfer timing. This approach which does not require direct memory

access (DMA) is designed for microcontrollers without DMA capability.

Except for pattern loading, SPI data transfer and Latch Enable generation, the code must

also contain the TX buffer Empty Flag test. This test must be taken into account if you

compute the total time necessary for all dimming operations.