Hi Alan, Thanks for adding Brennan to the discussion. My answers below.
Le lun. 30 oct. 2023 à 16:09, Alan C. Assis <acas...@gmail.com> a écrit : > Hi Bert, > > I'm CC Brennan (the original author) and Victor (the author of the > other driver using ESP32 RMT) they have more experience with WS2812. > > On 10/29/23, Bert Voldenuit <bertvolden...@gmail.com> wrote: > > Hi Alan, > > > > Thanks to your advices, I was able to find why board_ws2812_initialize() > > was not in System.map. > > Now it mounts and opens ws2812 driver. > > > > Great, what was the issue? --> I forgot to activate board_late_initialized --> By default the ws2812 driver allocate memory for each color (8bits) for RGBW (4 colors). My leds are RGB only so I had to change 4->3. I will try to add a parameter instead of a fixed value. > > > Indeed the SPI is not a piece of cake. I think I have it almost right but > > MOSI pin is idling high which is a problem for the reset which must be > low > > and I can' get it to the right timing. > > > > Exactly, using SPI to control the WS2812 seems challenging, you will > need to fiddling with it a little bit until get things working. > > > SPI frequency is set to 6MHz > > > > In ws2812.c > > I had to change WS2812_ONE_BYTE. I added one more 1 to fit the timing for > > SK6812 > > Target Measured (see Scope figure 1) > > T0H 0 0.3μs ±0.15μs 0.34µs > > T1H 1 0.6μs ±0.15μs 0.68µs > > T0L 0 0.9μs ±0.15μs 0.86µs > > T1L 1 0.6μs ±0.15μs 0.52µs > > Reset 80µs 20µs (Not Good) > > > > I'm not sure you need to change the number of bits, AFAIK it should be > only the frequency you should play with. SAMD21 (and many others SAM > chips) has a very advanced clock system (even compared with some > advanced processor) > --> True! I will try to fit the target by changing the clock without changing the bits > > I Changed WS2812_RST_CYCLES for 80µs but I still get 20µs, so it look > like > > it has no effect AND it is idling High (see Scope figure 2). > > > > Questions: > > > > - On Scope Figure 1, is it normal SPI is idling for 2.2µs between each > > byte? > > > > It could be caused by the driver itself. Maybe using SPI with DMA will > reduce this idle time. --> Ah! I thought it was already using DMA. Now I understand that the delay should be the cpu time needed to send the next bit. --> Yes using the DMA would definitely improve the driver. I checked on another library that it is possible to loop on DMA so when there is no data to send, it sends zeros forever at no cpu cost. --> I have no idea how to handle and allocate DMA. I saw a DMA trigger in the SPI option, will it be necessary to activate? I will try to add the DMA option in the driver. > > > - Is there a way to set idling Low Level? I looked in the datasheet > but... > > It looks like it is always high. > > > > I didn't find this option in the SPI_HWFEATURES. > > > - Should I create a WS2812_RESET_BYTE 0b00000000 and send x time so it > fits > > 80µs?? > > > > I think it could be an option. > > Brennan, what do you think? > > BR, > > Alan > Regards, Bertrand.
