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Topic: Questions about making a custom Arduino board (Read 970 times) previous topic - next topic

MetroExpress

Aug 17, 2010, 05:05 am Last Edit: Aug 17, 2010, 05:06 am by MetroExpress Reason: 1
So Im trying to go about condensing the arduino schematic for my project. But i've run into a few problems that I can't find a clear answer for. Hopefully someone on here could lend a hand.

1)  First off when going through the USB portion of the schematic I came across the Vin part of the board. Do I need it, cause it seems like its just for a header. And if I were to remove it how far back do I go in the circuit.

2) Also for the reset button in the bottom left corner of the schematic where does it go to, I see the USB and the capacitor / +5V in the top right using it where could I move the reset button too to get rid of the bottom right circuit?

3) The Solder Joint 1 (SJ1) in the USB circuit, what is it used for?

4) I don't want the standard power plug. Perferably just powered from a lithium battery, with the small two prong connector.
Any good links on incorporating that into the design?

eg. http://www.sparkfun.com/commerce/product_info.php?products_id=8483


5) Will I be able to load the boot-loader through the USB the way this schematic is set up? (Without the ICSP jumpers)

Thanks a bunch. Geoff :-)

And finally the Schematic


Grumpy_Mike

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Will I be able to load the boot-loader through the USB the way this schematic is set up?


No you can only load the boot loader using a programmer connected to MISO, MOSI, SCK, SS and reset.

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The Solder Joint 1 (SJ1) in the USB circuit, what is it used for?

For enabling / disabling the auto reset circuit when you cut the trck to disable it.
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Also for the reset button in the bottom left corner of the schematic where does it go to

To the reset pin (pin 1)?
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I came across the Vin part of the board. Do I need it, cause it seems like its just for a header.

Vin is the input voltage before the regulator . It is connected to the comparator to automatically switch the supply from USB to external power when an external power source is supplied.

A good example of a minimum arduino verses a bought one can be see if you down load the schematics from here:-
http://www.thebox.myzen.co.uk/Hardware/Pendulum.html

MetroExpress

Thanks for the quick reply. Few more questions while im at work :-) I will review everything tonight.


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For enabling / disabling the auto reset circuit when you cut the trck to disable it.


What is the default on the arduino mega board? Enabled?


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To the reset pin (pin 1)?


So if I was to pull the reset pin out of the schematic... Would the button still work? <- More research on my end is needed

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Vin is the input voltage before the regulator. It is connected to the comparator to automatically switch the supply from USB to external power when an external power source is supplied.


Same as the reset pin question, if I remove the pin that goes to the header on the regular arduino will it interfere with its operation. Cause i notice the schematic shows it running towards the vin but I can't see why it just goes to the VIN pin header. (Maybe im just very confused.)

Ill check out that link tonight, thanks for not flameing my n00bishness.

Graynomad

#3
Aug 18, 2010, 04:19 pm Last Edit: Aug 18, 2010, 04:31 pm by graynomad Reason: 1
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No you can only load the boot loader using a programmer connected to MISO, MOSI, SCK, SS and reset.

SS?

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So if I was to pull the reset pin out of the schematic... Would the button still work?

Not sure what you mean by "pull the reset pin out of the schematic", but if you want the button to work it must be connected to the reset pin (30 on the 1280, 1 on the 328).

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thanks for not flameing my n00bishness

No problem, we'll help if we can, but are you sure you have the experience to do this?

Truth is rather than seeing what you can take out of the Arduino circuit you may be better off looking at what you need to add to a bare chip to make it work (you don't need much actually) as it doesn't sound like you need much for your application.

I'm sure there's a a stack of "stand alone Arduino" threads here that can help.
Rob Gray aka the GRAYnomad www.robgray.com

nickvd

This is the schematic I use when I need to include an Atmega on a project's board.  It includes a simple 5-volt regulator (that can be ignored) as well.


nickvd

One note for the schematic that I just noticed... R9 (10k resistor) is pictured as a capacitor, I am not sure why eagle used that symbol..

MetroExpress

Ok so I've solved most of the problems the only real good question I can think of right now is. I have left the ICSP headers off of the schematic cause I feel they take up alot of room. Is there a way, or could someone explain to me how I could load the bootloader onto the atmega1280 without have to use the icsp headers. I've been doing some research on it but im just confused.

Thanks again guys :-)

Graynomad

#7
Aug 22, 2010, 04:21 am Last Edit: Aug 22, 2010, 06:07 am by graynomad Reason: 1
Dodgy way:
Have 6 pads say on the edge of the board (3 on top, 3 on bottom), then hold a header onto the pads for the few seconds it takes to load the program.

Less dodgy:
Same as above but solder the header then remove it. (no point really if it's a one-off boot loader job but ok for multiple application loads)

Best way?:
6 pads on the same side and make a small adapter using pogo pins, then press the pins to the pads for programing. This is how many professional products are programmed.

All the above still take up some room but not quite as much as a permenant header because the pads can be small and right on the edge of the PCB.


Rob Gray aka the GRAYnomad www.robgray.com

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