Author Topic: ATmega328p not running  (Read 382 times)

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Offline vockleya

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ATmega328p not running
« on: July 22, 2019, 02:15:20 am »
I'm working on a PWM-controlled LED lamp with full 0-100% dimming on 2 separate channels. It's based on an Arduino Nano and the ATmega328P.

This is the second iteration of the board, due to some layout and component footprint issues from the first version. I couldn't fit enough capacitance on the buck regulator output to keep it stable. This has been fixed in the latest iteration. The only things that have changed since the first version are some component selections (mostly footprint changes) and a rework of a few section of the layout.

The uC worked fine in the first version (I just powered it from the ICSP port), but now it just doesn't run. I don't even see anything happening at the oscillator pins. I have a few options for what is wrong, but I'm not sure where to start. The only thing that I can think of is a layout issue in the oscillator section, as that is really the only thing related to the uC that has changed between board versions.

I've attached the schematic and board layout in the hope that someone more experienced than me might see something. I had to hide the copper pours to make the board image intelligible, but there is a ground pour that fills the entire back of the PCB and a +5v pour on the left third of the top layer. There are also some small pours in the 3 power sections (U1-3) where things look disconnected.
« Last Edit: July 22, 2019, 04:11:11 am by vockleya »
 

Offline vockleya

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Re: ATmega328p not running
« Reply #1 on: July 22, 2019, 03:20:56 am »
Whoops. It appear that I forgot to actually attach the files.
 

Offline oPossum

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Re: ATmega328p not running
« Reply #2 on: July 22, 2019, 05:06:00 am »
Missing ground on pins 5 and 21.
Missing Vcc on pin 6.
No 100 nF cap near the '328 supply pins.
PCB doesn't seem to completely match schematic. No connection to pin 4 for example.
 

Offline vockleya

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Re: ATmega328p not running
« Reply #3 on: July 22, 2019, 05:28:06 pm »
Ah dangit. I knew there had to be something stupid that I forgot. I always seem to miss the bypass caps.

All the power pins are connected. As I said in the original post, I had to hide the ground and VCC pours to make the rest of the traces visible. And for some reason the "missing" power pins on the schematic are actually hidden under the other ones. A bit weird, I know, but they are all connected when the pours are visible.
 

Offline JDubU

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Re: ATmega328p not running
« Reply #4 on: July 24, 2019, 01:57:42 am »
Did you program the ATmega328 fuses?
 


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