Will this dev board schematic work?

Projects General Guidance
1

Hi there,

I have created a dev board schematic in Eagle with the ATmega328, can anyone tell me if it will work??

Thanks,

Will / Totara

328devboard.sch (788 KB)

2

You'll probably get more responses if you post a PDF as well. Not everyone has/likes Eagle.

That said I think you are good except there are no decoupling caps across the CPU power pins...oh I see you have a 10nF, 100nF is the standard size.

The Xtal is 6MHz, is that correct?

Rob

3

Thanks for your help Graynomad.

Graynomad:
The Xtal is 6MHz, is that correct?

Yep the crystal is 6 MHz.

Graynomad:
That said I think you are good except there are no decoupling caps across the CPU power pins...oh I see you have a 10nF, 100nF is the standard size.

I haven't done any of the power circuitry yet. Mostly because I want to check that design works before I change it all and include the FTDI chip, USB port and power jack. Also which caps do you think should be 100 nF?

Graynomad:
You'll probably get more responses if you post a PDF as well. Not everyone has/likes Eagle.

Thanks for that, when I upload the next revision of the schematic / board I will make sure to include that.

Also is it necessary to include a ISP programming header? I read somewhere that it is good practice. Can someone please link me to a schematic with a FTDI chip so I can work out my design? The main focus for this is making it into a really cheap (Hopefully under $10 NZD) development board that I can share with the community, and use in some of my projects.

Thanks,

Totara

4

Sorry,

Or would, instead of a FTDI chip, a ATMega16U2 be better? Like the Arduino UNO? Can I even get the code for that chip?

Thanks,

Totara

5

which caps do you think should be 100 nF?

Probably the 10nF one, at the schem level it's not always clear but on the PCB it has to be very close to the power pins.

is it necessary to include a ISP programming header?

Pretty much, unless you have another way to program the bootloader, eg if it's a DIP you can do that elsewhere and plug it in.

Can someone please link me to a schematic with a FTDI chip

See attached, but also the older Arduino schematics.

really cheap (Hopefully under $10 NZD)

Good luck with that, the FTDI chip can cost $7+, I've seen them for $14, best I've ever seen is $2.20 for 2000 off.

You may be better off with a header and having the user get an FTDI cable, that seems to be what you have now.

ATMega16U2...Can I even get the code for that chip?

I think it's on the Arduino site for download.

EDIT: Just noticed a typo in my schem, the 100pF caps should be 100nF.

Rob

ftdi-schem.jpg
ftdi-schem.jpg725×885 136 KB

6

Ok thanks for your help, I will now re-design the final schematic with the ATMega16U2 connected, the power circuitry then re-post it

EDIT:

I looked at the UNO schematic, I think I will go with a FTDI external module now :stuck_out_tongue:

Thanks a heap,

Totara

7

Sorry need a final last bit of help,

Can anyone point me in the right direction with how to wire the power? I was thinking that a standard DC jack will be fine, but I am not so sure how to add the capacitors and which pins it needs to goto

Thanks,

Totara

8

how to wire the power?

I looked at the UNO schematic

Look again, this time check out the power section.

Are you having a regulator? If so look at its data sheet to see what it needs.

Power normally goes to the middle pin of a DC barrel jack, GND on the outer.

I gotta say, if you are doing this as a learning project then fair enough, but there are so many cheap boards out there I wouldn't worry about other people using it.

Rob

9

Graynomad:
I gotta say, if you are doing this as a learning project then fair enough, but there are so many cheap boards out there I wouldn't worry about other people using it.

There's the question. In what way is your "dev board" to be distinguished from a genuine - or clone - UNO or Pro Mini?