Minimal components needed to run a Atmega328P IC

I’m working on an infinity mirror project that I found over on the FastLED feed. I was doing testing on an Arduino Uno, and right now I have it running on an Arduino pro mini and a digistump RTC kit, cobbled together on a generic PCB. Ultimately, for the final ‘product’, I’d like to use as little as I really need and put it on a custom PCB, which I’ve been working on. Before I can finalize the PCB, I need to determine what’s absolutely needed for the 328P to run properly and not give any trouble. I found a youtube video here That basically indicates that outside of the 328P chip, all that’s needed are two 22pF capacitors and the 16mHz crystal, and a 100nF capacitor in between the USB adapters DTR & pin 1 on the 328, which is only needed to allow the reset command from the USB > serial adapter to reset the chip for programming.

I then found another similar project that indicated that a 10k resistor is needed between pin 1 & +5vdc, and a 10uh inductor between +5 & pin 20, and a 100nF capacitor between +5vdc & pins 8 & 22. It also indicated that there should be 20pF capacitors in place of the 22pF capacitors indicated in the linked youtube video. If I were to search some more, I’d probably find about 10 other designs to run the 328P in a minimalist setup.

I’ve attached the relevant portion of my schematic. Does anyone know what is really needed for a 328P to run without issue (long term)?

If you can live with the 328 running at 8Mhz you can lose the crystal and 22 pf caps. That would be using the Lilypad boot loader with the internal oscillator. Then you just need the 0.1uf decoupling caps on the power supply inputs and a 10K resistor from reset to Vcc.

groundfungus: ...and a 10K resistor from reset to FCC.

If the target will not be reprogrammed in-circuit a wire / trace is a reasonable substitute leaving just the decoupling capacitors.

I run the 328 with 18 pF caps and 16 Mhz xtal wth a reset cao and push button to short Reset pin to ground through 270 ohm resistor. I have the DTR cap as welll. I bought a 328 wfith OPTIBOOT Bootloader from DIPMICRO.I upload sketches with a Sparkfun FTDI BASIC.

A lot on the subject with complete instructions.

Great writeup GoForSmoke, definitely bookmarking that! I was expecting to need to get a ISP programmer. Probably still will, but now I know how to program the blank IC with a bootloader without one.