As we want to use led strips for bouLED, trying to turn these LEDs on with our microcontroller would be a good start.
Our STM32L475 luckily happened to have SPI controllers. I used one in the frequency range recommended in the APA102 LED strip datatsheet, that is around 1MHz, to display simple animations on the ribbon. After some playing with the wires and some endianness considerations, I could control almost all of the 133 LEDs (and I’m investigating why some won’t obey).
Thanks to ChibiOS, the current implementation already makes use of the DMA, so that SPI transactions don’t take up much CPU time.
The next step will be to see if we can increase the frequency. Then we’ll need to consider more LED strips: the SPI controllers can only send data on a few GPIOs, while we might need to plug 20 LED strips (or less if we can put some in series).