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Topic: My first Arduino on a PCB (Read 5261 times) previous topic - next topic

gcm2

Hi all. After a LOT of breadboarding projects and BareBones/Diavolino, etc., I finally attempted to make my own permanent Ard on a PCB. Here's the board:

http://www.futurlec.com/Protoboards.shtml#PROTO777     the top one. Real cheap but takes 3 weeks.

I really took my time planning and careful soldering and all went well after all. This was fun!

There's a bare wire jumper I thought I needed between Reset pin and the reset button - same circuit as the 0.1uF blue cap. I found out this would not allow my upload to work, so I cut it...

I plan on adding a LCD to the remaining top of the board.



CrossRoads

Good start!
Uses a resonator?
I would also suggest 0.1uF caps from Vcc, Acc, and Aref pins to Gnd.

You appear to have Aref connected to +5 - remove that, not needed. Just a cap to Gnd.
Aref connects internally to Vcc - if you hardware it to +5, you cannot connect it internally to 1.1V.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

gcm2

Thank you! I had a resonator on hand, seems to work fine - have used on other breadboards as well as the oscillators.
I will make the changes you have advised.
Just curious - this page
http://www.arduino.cc/en/Main/Standalone
shows Aref connected to +5 power - not needed at all?

janost


CrossRoads

No, Aref should not be wired to +5. It can be connected to Vcc internally (default setting in the IDE), it only needs 0.1uF cap to gnd.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Chagrin

You can connect Aref to 5V, but if you do then you can no longer use an analogReference() that is anything other than EXTERNAL. For example if you had 5V connected to Aref and set analogReference(INTERNAL) then you would be shorting the internal 1.1V to that 5V. Magic smoke, etc.

gcm2

Thanks all. I think I understand Aref now... I don't think I have ever used AnalogReference(INTERNAL).

CrossRoads

Internal Aref, 1.1V, is good for lower level signals.
1.1/1023 = 1.07mV per step vs 4.88mV/step if Vcc = 5.0V.
Vcc may vary, especially if from USB, which is spec'ed at 5V +/-10%, so 4.75 to 5.25. Plus there may be varying loss thru the PTC fuse, which has some resistance, thus a varying voltage drop across it depending on current load for the rest of the board.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Pedro147

Good job. It is a thrill when you make your first standalone board  8)  Making your own home etched PCB's next?
http://www.pedroduino.com

gcm2

Thank you! And thanks for the explanation Crossroads.
I don't think I'll get into the making of home etched. From what I have read about the how-to's, too complicated for me!

janost


Thank you! And thanks for the explanation Crossroads.
I don't think I'll get into the making of home etched. From what I have read about the how-to's, too complicated for me!


Don't say that.

It's actually easier than it looks. :)

janost

The Arduino UNO is actually a breakout board for a 28-DIP chip.
Yes, your ATmega328 on a perfboard.

It does have onboard FTDI but that's about it.

Pedro147

#12
Apr 20, 2014, 12:39 am Last Edit: Apr 20, 2014, 12:41 am by Pedro147 Reason: 1
janost is right it really is not that difficult and you do need very much equipment to do it. I was surprised at how quickly I could "Knock one up" Here are a couple of my simple boards.
http://www.pedroduino.com

janost

That is the reason I moved to the NXP LPC812 ARM Cortex.
No need for an Xtal, No nothing. Just 3.3v and it runs.
And fast to.

I still do things on the ATmega platform because its easy and it does have a great IDE.

If your are serious (you are as you did it your self) you get your self an ISP programmer and work with the 1284P.
Much more fun and plenty of SRAM and GPIO.

CrossRoads

#14
Apr 20, 2014, 05:06 am Last Edit: Apr 20, 2014, 05:08 am by CrossRoads Reason: 1
1284P is easy to wire up too. Here's my prototype board, and the duemilanove style PCB of it with an FTDI module.
0.1uF caps on VCC, AVCC, Aref, and DTR to Reset,
10K reset,
16 MHz crystal,
22 pf caps.
And headers.  Not much to it!
http://www.crossroadsfencing.com/BobuinoRev17/


Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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