How many layers has this thing got? There appear to be 4 signal layers (red/blue/brown/green) plus groundplane - maybe it's 6-layer with two planes in it? That much is OK, if a little unusual, but there appear to be cutouts in the planes under the RP2040 and flash chip.
I don't know if this is just an artifact of how you generated the plots, but if it's real then it's a very bad idea and could just possibly be the source of your problem: it looks like the RP2040 ground is only connected via a skinny little track on the green layer, when it should really be a solid connection to the groundplane.
A common failure mode with badly-designed 2-layer boards is that the RP2040 runs OK in bootloader mode, but crashes when real code is loaded: the bootloader runs the CPU at low speed and the flash in both low speed and 1-bit-wide mode, so using much less power and at lower frequency so that deficiencies in the grounding have less effect, but when application code tries to run at full speed it fails.
Also, you seem to have economised on the number of decoupling capacitors, and gone up to 0603 size (though some of them are 0402??) both of which are a bad idea though not necessarily fatal.
I don't know if this is just an artifact of how you generated the plots, but if it's real then it's a very bad idea and could just possibly be the source of your problem: it looks like the RP2040 ground is only connected via a skinny little track on the green layer, when it should really be a solid connection to the groundplane.
A common failure mode with badly-designed 2-layer boards is that the RP2040 runs OK in bootloader mode, but crashes when real code is loaded: the bootloader runs the CPU at low speed and the flash in both low speed and 1-bit-wide mode, so using much less power and at lower frequency so that deficiencies in the grounding have less effect, but when application code tries to run at full speed it fails.
Also, you seem to have economised on the number of decoupling capacitors, and gone up to 0603 size (though some of them are 0402??) both of which are a bad idea though not necessarily fatal.
Statistics: Posted by arg001 — Wed Jan 22, 2025 8:52 am