So about a month ago I found a 200mm*200mm 100W fiber laser on Aliexpress for $3100, half off of (presumably) $6200. My googling suggested that $6000 was a normal price, so $3100 was a steal, if true. After some waffling, I went for it. I took some pictures of the components, did some testing. Overall, … Continue reading Vevor 100W Galvo Fiber Laser Analysis
Notes
Raspberry Pico fail to boot from flash
So. If you should find that the code runs from the debugger, but does not start on its own when you plug in the usb, add to your rootmost CMakeLists.txt set(PICO_BOARD pico_pair) referencing pico-sdk/src/boards/include/boards/pico_pair.h and if you don't have that file, just copy pico-sdk/src/boards/include/boards/pico.h but add these three lines near the top, after the name … Continue reading Raspberry Pico fail to boot from flash
General PCBA notes
Often specifically about JLCPCB and KiCAD. If a crystal says 20pF, it probably actually wants caps of 35pF each. C = 2L-5pF, or so. Then pick an available capacitor near that value. JLCPCB's understanding of 45* rotated components is 90* off of KiCAD's, in some way. ...But only on the pcb bottom? Expect also disagreements … Continue reading General PCBA notes
Crystal oscillator capacitors
Apparently a crystal oscillator marked "20pF" DOESN'T get 20pF caps, it gets ~35pF caps. (In the usual microcontroller's oscillator configuration, anyway.) My rule of thumb, now, is C=2L-5pF. See https://electronics.stackexchange.com/a/677202/166296 .
Raspberry Pico GPIO latency
Fyi. Writing Pico PIO code. A read from a GPIO takes...3.5 clock cycles. I think. (Plz no sue.) I tested several wildly different clock speeds. You can do INPUT_SYNC_BYPASS with `hw_set_bits(&PIO->input_sync_bypass, 1u << PIN);` and it goes down to like 1.1 cycles, but the docs warn the PIO could summon nasal demons if it reads … Continue reading Raspberry Pico GPIO latency
Highly Questionable Ideas 