No small 100nF capacitors. Only a bulk 1uF and 10uF capacitor inches away. Very inefficient layout. Is that just a 10 Ohm resistor connected to a physical switch to control the backlight? DC-DC module? He's got a PCB on there already, it shouldn't be that much harder to slap down a Buck converter himself.
What size components are those? Far larger than 0805, they might actually be like 2012 (inch) components.
Good grief. I guess Microchip / Atmel chips are legendary for this reason: they always were considered braindead easy to boot. But this is the higher-end Cortex-M7 series chips, I'd imagine that you'd need at least a _bit_ more care with regards to decoupling and power-delivery to achieve reliability than what he did here!
No seriously. A 300MHz processor with _NO_ local decoupling capacitors? Is he mad?
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But then again, I guess there's something to be said about making a board "easier" and through less effort. I guess there's no reason to be a masochist with 0603 (or smaller) parts when prototyping.
Also the device worked even when it was on a breadboard, suggesting he made reasonable technical decisions regarding placebo capacitors.
This other post (https://lcamtuf.substack.com/p/mcu-land-part-3-baby-steps-wi...) has more information with his experiments with SAMS70, suggesting experimentation with a breakout board. So same same overall but...
He's upgraded to the SAMS70 which is 300MHz. Its a totally different class of processor.
> Also the device worked even when it was on a breadboard, suggesting he made reasonable technical decisions regarding placebo capacitors.
I dunno. PDN (power-delivery network) issues are really complex. You solve a lot of headaches with a 1-penny 100nF capacitor here and there.
I'm very curious what the SAMS70's onboard capacitance is. I'm wondering if Microchip/Atmel goes overboard on onboard capacitance or something.
In any case: the documentation from Microchip is clear about this. 100nF capacitors on every input pin. I don't see any reason to stray from this, its not like 100nF capacitors are expensive, or even difficult to solder.
The DC-DC module also seems like a sensible choice for hand assembly. These things cost about a buck or two these days.
This board is clearly meant to display the electronic components in plain view and be easy to solder at home.
The Microchip documentation for the SAMS70 literally recommends 15x 100nF capacitors, as well as a 4.7uF capacitor for the buck converter, and a second 4.7uF bulk decoupling capacitor.
That's 17x capacitors if you're just following the manufacturer's recommendation.
https://onlinedocs.microchip.com/oxy/GUID-174CB4CE-C435-49E8...
The board as shown in that blog has ZERO of them. Madness. Each 100nF capacitor "should" be directly adjacent to the power-pin its decoupling, fractions of a mm away. And to make sure there's enough room for everything to go on (fractions of a mm is very small), you want to use 0603, or 0402, or smaller parts just for convenience.
But 0603 is already troublesome for hand-placing IMO. (though the even smaller 0402 is still possible in my experience). So as I said, it starts to get masochistic with these sizes IMO. But still, I'd personally try to get at least a decoupling capacitor on each power-pin as the documents recommend (even if its a larger 0805 or bigger).
In any case, the ~4 capacitors that he places is very much on the low-end compared to the ~17 recommended.
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> They are more cost-efficient, but they're more work to solder by hand.
These are all surface mount parts, which means you're soldering using frying-pan and/or toaster-oven at this point.
Or at least, you _SHOULD_ be doing that (or maybe get a real hotplate, lol. But my pancake electric griddle works perfect). Its way more convenient.
You apply the solder paste. Then you drop the capacitor into place with tweezers, and the solder-paste is sticky enough to "grab" the capacitor. You then place all other components. Easy-peasy.
Heat the entire board to 330F (assuming low-melt lead-free solder) using the frying pan for 10-seconds and done. Some people like adding a 1/4" aluminum plate to make the heat more consistently applied.
Components are designed for 500F for 10 seconds btw (aka: standard lead-free solder). So you have a lot of leeway with regards to the frying pan method in practice. But you should keep a strict timer as some parts are really sensitive to that "for 10 seconds" requirement. A proper reflow oven and/or hotplate obviously does the job better with automatic controls, but this is all slow enough that you can do it by hand by just turning the dial up/down with a stopwatch in your hands.