Tag: displays

Getting real console frames from the H7 to the Feather RP2040 DVI took two days and five separate root causes: a CPU-starving encoder, a FIFO race, a missing ground return, a clock divider that lied to me, and a GPIO port that mutes my DAC.

The Feather RP2040 DVI arrived this morning and had the console's palette on a monitor within 45 minutes of hitting the bench - after a wrong-variant pinout diagram, a factory firmware with no drive, and a 3D printer slicer typing G-code into my REPL.

I wanted to redesign Rusty Nail's boot splash, but the standalone build sends nothing back to a host - the panel is the only display. So before I could change the splash, I had to work out how to screenshot a screen my Mac can't see.

I bought a 50-pin RGB888-to-HDMI board for the fantasy console, then counted the pins. Two of them are Ethernet, three are the audio bus, and the Nucleo never had 24 to give. The fix might be a second microcontroller whose whole job is HDMI.

The SPI blit was a blocking, row-by-row write that stalled the whole console for about 13ms every frame. DMA fixed that, the data cache nearly broke it, and a frame I was packing for nobody was the last easy win. About 14fps to about 41fps.

I had a working HDMI path at 12:48 in the morning. Then at 10am, well rested and full of hope, I picked up the tiny SPI screen instead and spent nine hours reinventing flicker. A note on patience, and on why hardware scanout is the thing I should have just waited for.

Getting the desktop off the USB stream and onto a real LCD. A dead-end controller that latches on the wrong clock edge, a switch to the ST7735, and climbing from 1 MHz to 25 MHz without losing the audio.