Low cost ATmega128A-based arduino-compatible PCB with original "Wiring" form factor.
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This zip contains both the rev0005 (with 0004-compatible connector placement), and a new rev0006 with UBC "Tinah" (also rev0003?) compatible connector placement. "alpha2" gets the teardrop fixes and some minor silkscreen movement.
Zip Archive - 1.12 MB - 03/06/2018 at 10:10
That 2nd board is now more-or-less fully assembled, and I built up a 3rd board with an ATmega1281 (same pinout, mostly - sort-of a superset.) The SMT soldering is getting easier with practice (go figure!) The 1206/0805 LED footprints also work pretty well for some PLCC2 LEDs I have surplus of, so that's nice...
In the course of working on the variants/pins_arduino.h, I discovered that I'd mis-labeled the upper-right connector. These are "digital pin 48-53" on the Sparkfun and newer boards, but on the old-style Wiring boards (up through v0004, and this one) this is a "PWM" connector that is paralleled with some other pins, and DP48 is the built-in LED. So those have been changed, and I added "49" and "50" for the 2-pin PG connector. I've adjusted the regulator package drawing.
Oh, I also stopped working on my variant, in favor of using https://github.com/per1234/wirino that another Arduino user had already developed.
The USB module is mounted and working; uploads now possible using the megaCore version of optiboot, over the USB. I was hoping the the RX/TX LED on the module would be visible even though it's mounted upside down, but it looks like it's mostly overpowered by the "power" LED that is also on the module. the module fits really nicely against the board, and it seems like the way it is mounted will improve the physical robustness the way that I had hoped.
The USB Module could be slightly closer to the edge of the board; right now the board edge is almost exactly even with the micro-USB connector, while I'm used to having them jut out slightly. OTOH, maybe this is good.
The 7805 footprint seems to be a little "short" for most of the regulators I have, and since I'm using the groundplane as a heatsink anyway, I don't see why the mounting hole shouldn't be plated through and shorted to the tab... (ah; the tab isn't included in the EAGLE package at all.)
The second "minimal build" attempt is blinking it's onboard LED (powered and programmed via ISP connector.) (pictures posted)!! Working on the "variant" file...
The first attempt seems to have power and ground shorted, demonstrating that my SMT soldering skills are lacking, even with the 0.8mm LQFP that I was hoping would be relatively "easy." Sigh. I seem to have trouble getting the pins to line up on all 4 sides at once (at least with either pin-at-a-time or drag soldering using an iron.)
I guess it's time to break out the hot-air system I bought a while ago. But I need younger eyes and two right hands...
PCBs have arrived! (and some parts, too.)
They look nice, and I'm impressed with the turnaround time (I did opt for DHL shipping, which dominated the costs of the two designs I had ordered.)
Photos (well, scans, so the lighting is bit odd) have been added to the project.
Hmm. Noticed (after ordering the PCBs, of course) that the circuit does not include the 1k "isolation" resistors in the Serial RX/TX lines to the USB converter, that have become relatively standardin arduino-like boards...
Parts (Microchip, Aliexpress) and PCBs (PCBWay) have been ordered.
(I already have some of the CH340F modules. "they're so cute!")
Notes to self:
v0006 has been uploaded and should have connector placement compatible with the UBC "Tinah" shield (which is supposedly compatible with Wiring 0003.) The same zip file has the v0005 with the slightly newer pinout.
Aside from the changed placement of connnectors, the older board does not have an Analog Reference input; only (apparently) power pins on that connector (which has only 4 pins in that rev.) There is in fact not room for the new 6pin connector (it runs into the mounting hole), but I changed it to a 5pin connector with Aref "squeezed in."
The V0001 (?) picture that's floating around shows a 10pin JTAG connector in that location, BTW. It's a shame that the history of the changes between the initial version and (say) the Sparkfun version have been lost.
Hmm. Ok, this project was initially spurred by a request on the Arduino Forum, from a university using old Wiring Boards (V0003) with a custom-made multi-purpose "shield" ( http://forum.arduino.cc/index.php?topic=529695.0 ) This shield wasn't compatible with the newer Wiring boards (not even the Sparkfun version), even if those had been still available. Obviously the solution is to take the open source design and manufacture them yourself. Which would have worked fine, except that the V0003 design doesn't seem to be around any more :-( (V0004 is on the Wiring.org.cc site.)
As it turns out, several of the important connectors moved around between V0003 and V0004, so the V0005 design I published WILL NOT WORK for anyone who was hoping to have a board compatible with V0003... I thought I should put that warning here, just in case. Still considering what to do...
(Insert tirade about the importance of revision control in open source projects...)
Eagle source, gerbers, printable (pdf/png/etc)
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