Atmega 328 and TLC5940 routing

I’m trying to build a barebones pcb layout just to drive the tlc5940 (standard pin layout.)
Im going to have to run a few jumpers for some of the wires but have I connected what I’ve done so far correct?

Is this going to be etched?

What’s the overlap in the red circle?
Also I am assuming the 2K resistor is going on the under side of the board?

I am guessing that you don’t have a schematic?

codlink:
Is this going to be etched?

Yes

codlink:
What's the overlap in the red circle?

Another resistor goes here

codlink:
Also I am assuming the 2K resistor is going on the under side of the board?

No, unless ic sockets have changed over the years It should fit in the middle of the base.

codlink:
I am guessing that you don't have a schematic?

Using the breadboard layout on the libs google code page which has given me the working prototype.
I'm just sruggling with the conversion from arduino to minimal 328 circuit.

Using the breadboard layout on the libs google code page which has given me the working prototype.
I'm just sruggling with the conversion from arduino to minimal 328 circuit.

I can say that not using a schematic to route the PCB in Fritzing has gave me quite a few boards that are now coasters. Designing a schematic in Fritzing is next to impossible. Just make sure you re-recheck your routing on the PCB. I dropped Fritzing because of it's schematic downfalls. If you plan on making more PCBs, I would highly suggest moving to Eagle.

Next question, are you planning on programming the 328 in an Arduino and moving it over?

The 2K resistor should be exactly half way between the rows. Unless your sockets look different than mine.

codlink:

Using the breadboard layout on the libs google code page which has given me the working prototype.
I'm just sruggling with the conversion from arduino to minimal 328 circuit.

I can say that not using a schematic to route the PCB in Fritzing has gave me quite a few boards that are now coasters. Designing a schematic in Fritzing is next to impossible. Just make sure you re-recheck your routing on the PCB. I dropped Fritzing because of it's schematic downfalls. If you plan on making more PCBs, I would highly suggest moving to Eagle.

Yup I noticed schematic view is hopeless that why I only use BB or PCB view.

I posted here because I don't know where else to ask to get someone to check out my wiring.
Eagle is not in the Mac apps store.

http://www.cadsoftusa.com/download-eagle/

Well Eagle is so unfriendly it's crap, without a ton or reading I cant even get started.
Fritzing keeps putting things in the wrong place.
Screw that where my copper clad stripboard.

It's not that it's unfriendly, it's got a ton more options than Fritzing. You can do alot more with Eagle. Also, there are Eagle tutorials that can get you started. Just search Google. I learned and made my first PCB in Eagle in less than a day.. I started with Fritzing and it's good for beginners, but once you design more complicated boards, Fritzing lacks.

Crystal is rather far from the processor. I believe Atmel recommends as close as possible with a ground plane.

No bypass capacitors?

I believe the TLC5940 datasheet calls for a capacitor of several microfarads across VCC and GND.

Ah yes, bypass caps.. I can't believe I missed those..

Now that I missed because I didn’t see a referance for it on the sheet (still trying to understand it tbh) but the arduino prototype doesn’t have one.

Codelink - still building the schematic for this :astonished: =(

AJB2K3:
Codelink - still building the schematic for this :astonished: =(

Eagle my friend, Eagle.

I prefer DipTrace, and I've been using it for the last year for my personal projects. I know Eagle might be more powerful and has a gigantic user base, but I like DipTrace better. The free version is great and should be enough even for more advanced hobbists.

Back on topic: ditch that layout, since there are several problems with it:

  • the crystal is too far from the 328
  • there are sharp corners in the traces. Never, NEVER route traces with 90º angles.
  • there is no bypass capacitors for either chip
  • it is good practice to use every space left in the board (in its signal side) for a copper pour linked to the ground net.

If you decide to go ahead and use that circuit anyway, that one is easier done with a perfboard, rather than etched. Make use you use DIP sockets, instead of soldering the chips directly to the board.

AlxDroidDev:
I prefer DipTrace, and I've been using it for the last year for my personal projects. I know Eagle might be more powerful and has a gigantic user base, but I like DipTrace better. The free version is great and should be enough even for more advanced hobbists.

Back on topic: ditch that layout, since there are several problems with it:

  • the crystal is too far from the 328
  • there are sharp corners in the traces. Never, NEVER route traces with 90º angles.
  • there is no bypass capacitors for either chip
  • it is good practice to use every space left in the board (in its signal side) for a copper pour linked to the ground net.

If you decide to go ahead and use that circuit anyway, that one is easier done with a perfboard, rather than etched. Make use you use DIP sockets, instead of soldering the chips directly to the board.

I have moved the crystal under the board and added the bypass to the tlc5940
Still playing with layout designs.
Need to order some electronics to check out part size's

and added the bypass to the tlc5940

The processor also needs them.

Where? i haven't seen one any ware?

Page 2: 2.1 Digital supply section.

Page 14: Figure 6-1...

Decoupling on all VCC/GND pairs

Put a 0.1uF capacitor across all (A)VCC / GND pairs as close as possible to the processor.

?? not on here?

Stupid additional question but I plan on running this of a 3.6v PSP battery (always have 2 spare in camera bag + 1 in each of my psp1001 consoles)

Am I supposed to change some component values?

Stupid question and you have permission to roll your eyes.

AJB2K3:
?? not on here?

Arduino - Home

The bypass caps are there (2 x 10uF caps): one is in the output of the 7805 voltage regulator. In all the pictures where the breadboard appears with the 7805, the bypass cap for the Atmega328 is the upper rightmost cap. Note that the 7805 also requires an input capacitor and it is also there, to the left of the other capacitor, also 10uF.

AJB2K3:
?? not on here?

Unfortunately, it is a common mistake to exclude them.

With those two digital chips on your board there is a high probability you will have problems without the bypass capacitors. If you do not include them and have problems you will be pulling your hair out trying to figure out what is wrong.