Problems with DIY Barebones Arduino Circuit Board

Using Arduino Project Guidance
#1

I need suggestions on how to troubleshoot a new circuit board.

I’m havng a problem getting my first Eagle-designed circuit board to work properly (at all, actually). I have completed a few dozen Arduino/ATMEGA328/ATTINY85 projects, mostly on protoboard. I have successfully etched (someone else’s design) circuit boards about 6 times, but this is my first attempt at a sort of “Barebones” Arduino of my own. Please understand that, as a hobbyist, I have some things I understand, but often have huge, gaping holes in my knowledge of electronics.

I’m tryng to make a circuit board for a cellphone based on Adafruit’s Fona module, a keypad, an OLED display and an ATMEGA328. Currently, I’m only trying to get the OLED and keypad working, and I have this working on a breadboard. The ATMEGA328 program is loaded from an Arduino with a ZIF socket and then placed in the breadboard (see picture). On the breadboard, I only have a 16Mhz crystal, two 22pf caps and a 5V power supply fed by a 9V battery. No other components to make up the circuit - no other capacitors/resistors no reset switch. This breadboard version works to my expectation showing messages on the OLED and with the keypad working.

When I insert the programmed ATMEGA328 into the circuit board version, I don’t see any text on the OLED.

What I have done to troubleshoot:

  • checked traces for continuity: OK
  • checked voltage at all entry points: OK
  • fed the IC socket with jumper wires directly from the breadboard version, works! Pin traces are/should be OK
  • crudely patched in a 0.1uf ceramic cap between 5V and AREF to GND - no joy

Any help or suggestions gratefully accepted…

atmega328_keypad_v4.pdf (14.2 KB)

breadboard.jpg
breadboard.jpg2448×3264 1.38 MB

DPC_troubleshooting.jpg
DPC_troubleshooting.jpg615×820 47.6 KB

#2

There is not enough information in your post for forum members to troubleshoot for you, for example, how do you know that the ATmega is properly programmed?

However, some pointers: it is a serious mistake to leave out bypass capacitors and any necessary pullup resistors, like the reset circuit. Check the voltage on Vcc. You can at least check whether the crystal oscillator is functioning by probing the appropriate pins with an oscilloscope.

#3

Yes, you need de-coupling as mentioned.
Try programming the simple blink sketch with pin 13 to see if it works.

#4

Thanks

#5

Upon re-reading your post, I think I missed that (supposedly) the exact same circuit functions when assembled on the breadboard, but not on the PCB. If that is correct then most likely, either the crystal oscillator is not working or there is a break or misconnection on the PCB.

However, keep in mind that breadboards and PCBs are not identical environments, partly due to fairly large stray capacitances between connectors on the breadboard that are not found on a PCB.

#6