audio
- FiiO X1 PCM5142 DSP blocks: the flat head I believed
Three FiiO X1 firmware blocks the DAC loads per stream looked like passthrough filters, until the decoder read all 2,708 bytes of each one.
- FiiO X1 EQ table: seven register bytes my generator never read
Decoding the FiiO X1's PCM5142 EQ coefficient table: the format was fine, the register bytes were not, and my first proof of the layout was wrong too.
- FiiO X1 bare-metal audio: four GPIO offsets, all wrong
A bare-metal sine-wave test for the FiiO X1's PCM5142 DAC built clean; two code reviews forced 16 fixes, including four GPIO offsets. None of it ran.
- FiiO X1 EQ presets: floats in .data, not a NAND cache
Ghidra shows the FiiO X1 never reads its eq.ini back: preset gains are floats in .data, reloaded each boot. Nine new presets showed after a factory reset.