Since the USB PLL can generate an accurate 48MHz from 12.288, I've sometimes considered the idea that for a unit that wants to have USB while running, it would be possible to use the bootrom for programming by having a programming tool which has another RP2040 also with 12.288MHz xtal and so run the USB at 12.288Mbit/sec in place of the usual 12Mbit. I haven't got around to trying it, but it would almost certainly work.
And yes, all my RP2xxxs run on 12.288MHz crystals.
I have implemented the Picotool protocol against TinyUSB (ie. running on a RP2040 to load software into another one), which I use for a slave device without flash, and that was easy enough.
Edit: or actually, a stock Pico with 12MHz can generate 49.142857 against the 49.152MHz needed to match the one with 12.288Mhz, only 0.2% error - not good enough for audio, but quite likely good enough for USB to work.
Statistics: Posted by arg001 — Sat Nov 30, 2024 2:38 pm