Tag: firmware

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.

An I2S DAC, SAI plus DMA, and three gotchas that each ate a session: a mute pin nobody pulls high, a data cache fighting the DMA, and an async executor that starved the audio to silence.

Vendoring Lua 5.4 into a bare-metal firmware, the 64-bit integer bug that printed 42 minus two-to-the-32, and why a hardware watchdog beat an instruction-count hook for stopping runaway carts.

Rusty Nail is a windowed pixel-desktop OS running bare-metal on a Nucleo-H753ZI. How it is put together, and why the display layer is an abstraction from day one.