Hello All,
I wonder if someone here can help me out. I have spend a large number of hours over a few days on and off trying to drive a bitstream into a WS2812B using DMA. I have proven the hardware by bit-banging into the LED and it works as expected. I have the DIN pin of the WS2812B to PA3 configured for TIM2_CH4, this is a clean project with nothing else in the way. Clocks are configured to the point where I can get the expected frequency/duty cycle I need, and I have 24 bytes of static data that I want to send to the PWM CCP to create a bitstream.
The code is below, I have gotten this far be reading, seeing examples, even chatting with Chat GPT, and I just cannot get this to work. The code below yields nothing out, its just always low. If I enable the PWM by uncommenting lines 102 and 103 I get the expected 803Khz at 50% mark/space.
In my main loop I am trying to trigger a DMA transfer once ever 500ms... but it does not work, and I am at a loss as where to go now, have followed lots of examples and tried lots of poking around with things, but I just cant seem to make this work.
Can anyone help or offer me any pointers please?
Gerry
@TDK thanks for the pointer, thats one of the many examples I came across and tried. The problem I have is not so much driving the Ws2812B (although thats what I am trying to do), the problem is, I cannot get the DMA transfer to work. That being said, I just added the following from the above example, and I can see that the something is happening, my main loop runs, and once ever 500ms I clear the variable, initiate the DMA transfer and then check this value, and, it gets reset to 1 by the callback function, so that suggests the DMA is running.
However, what I see on the scope is a fast rising edge and a slow decay of about 1ms, no actual data. Keeping in mind that if instead of doing any DMA transfer I just start the PWM by uncommenting those two lines, I get the 803khs output as expected.
I am really quite lost here, it should work, the change I made appears to show that the DMA peripheral is being started, and is signaling a stop, I am just not seeing the PWM data stream on the output pin.
I am obviously doing something ***, but I really cannot figure out what :(
And for comepleteness, this is the TIM4 output when I enable PWM by uncommenting those two lines, this is really just to prove the hardware setup and timer confiuration.
