I'd like to start yet another rehash of DIY Arduino. This time with a pcb that is within 5cmx5cm size so that iteadstudio will build it for $1.40 in packs of 10.
The actual shield size is a fraction of an inch bigger so female headers bend just slightly.
You will need an atmega328 or atmega168 with bootloader flashed, and a CP2102 which is a $3.00 (ebay) usb to serial converter, which has been slightly modified to connect dtr to reset line.
Actual cost is about $7.00: pcb: $1.4, atmega328: $3.30, other parts about $2.00
Your projects seem to consistently use those 2-termial ceramic resonators without the usual caps to ground. Does that seem to work with reasonable accuracy?
I picked to the ceramic clock mostly for price. I didn't realize there was a potential issue with not having a ground pin.
I would have to compare to a build with a grounded clock to see if it behaved differently.
I do know that driving some dc motors, depending on load and weak batteries the system can occasionally lock up. I got around this issue by using pwm outputs to hbridge and lowering the duty cycle.
You could take my schematic and change the clock to a 3 pin clock, or I could post one for you if you are not familiar with Eagle.
If it's a design you're giving out, or especially selling pre-manned boards, I would vote for having that ground pin hole. It may work without, but you're probably out of spec on the ideal load capacitance of your oscillator. And after all, it's harmless if you don't use it yourself.
I picked to the ceramic clock mostly for price. I didn't realize there was a potential issue with not having a ground pin.
Have a look at this site for low cost low volume parts: http://taydaelectronics.com/
They have 3 pin 16Mhz ceramic resonators for $0.17 (20Mhz are only $0.08)
Resistors/diodes/Caps are mostly $0.01
I replaced the 2 pin 16mhz resonator with a 3 pin resonator.
I created an interactive .htm page. This page has mouser and other supplier links to all the components. Let me know if you have any comments.
Thanks, http://atmega.site40.net/ShieldWeeny.htm
Paul
That sure is a lot of vias you used. Did you use an autorouter? Also see a lot of right angles in your tracks. Not a god idea for noise, but thats just my opinion. Looks good otherwise though
Yes, I used the autorouter. I'm not sure how to do manual traces so I guess we are kind of stuck. I also looked at the firefox browser and I'm not sure what's happening there either.
Paul
You will need an atmega328 or atmega168 with bootloader flashed, and a CP2102 which is a $3.00 (ebay) usb to serial converter,
I would suggest that you get a real avr programmer and be done with that usb2serial stuff. And you can always reuse your programmer on future project, and no need to buy an avr with bootloader flashed - with your own programmer, you can flash whatever you want.
I have my own tinyisb avr programmer for flashing the bootloader
usb2serial is nice because it is external to the board and can be removed when your program has been flashed.
