the idea of your program

[schhqq]

Hello, Mr. can you briefly describe the idea of your program?

[efthym]

Hi. I've studied this repository recently for a similar project that I am planning. The main code regarding the led matrix is in matrix.c.

Here's the outline of how I think it works. Two operations happen in parallel after each latch/strobe pulse (which copies the scanned in data from the shift register to a latch/register):

• The scan-in of the RGB pixel data using DMA. When all data have been scanned in, an interrupt handler is called (DMA2_Stream5_IRQHandler)
• A timer (TIM3) is set which outputs the OE (output enable - active low) immediately and after some time OE becomes high (stop displaying) and an interrupt is triggered calling (TIM3_IRQHandler)

The above interrupt handlers must synchronize when the next latch/strobe pulse will happen (to load the just scanned-in data of a row). The last one of these handler to arrive, calls matrix_next(), which handles the latch/strobe pulse and prepares the next DMA transfer and the next timer-controlled OE pulse.

Initially I was buffled by the use of another timer (TIM1) in the code. This is set to trigger each DMA transfer. Normaly the DMA is triggered by a peripheral when it is ready to send/accept data. However the GPIO does not have this capability, hence the use of TIM1.

[Frans-Willem]

In case either of you is interested, I know I wrote a blog post at the time writing down my thoughts and why I ended up the way I did here:
https://fw.hardijzer.nl/?p=223