{Avr|Pic}Stamp

[Bertho]

Hi all,

There are often things you want to test quickly when designing something. Most of the time you need some set of I/O pins (often more then fewer) and some quick-and-dirty debugging (i.e. serial) to get going. I was approached at the local hackerspace OSAA if it was not possible to make a few simple boards which would be cheap, have a lot of I/O pins and a serial port via USB. The target was set at about DKK 100,- (that is Danish kroner); or about $18,-. With the price-target set, we had to choose not to go the Arduino route, as they are much more expensive.

What I came up with is the following:

Front view

Back view

There are (for avr) 32 and (for pic) 36 I/O lines available on the two 19-pin pin headers. The power can be supplied via USB or injected on the header. It includes a 3V3 regulator (as it uses 3.3V signaling) and a serial/USB converter which can be disabled/detached via 0R resistors. The CPUs used are ATMega32A and PIC18F45K22, which are powerful and have lots of functionality and memory. Both processors run on a 16MHz crystal.

Both PicStamp and AvrStamp have about the same pin-layout on the headers. Ports B/C are swapped between AVR and PIC because of the chip-layout. The pic version has some port E pins where there lack the high bits of port A and the avr has an analog ref pin. However, the boards are basically swap-able if you take these small differences into account and the TX/RX pins which are located at different ports for avr and pic.

I programmed a Blinky program to flip portA.bit0 and included serial comms as a quick test.

Test setup with "blinky"

The schematic diagrams are available on my site at http://www.vagrearg.org/content/avrpicstamp and some more notes on the development. The complete PCB sources will also be available when the design is stabilized (or send me a PM). The design is CC-BY-SA-3.0.

The price-target can be met for these small devices when I can produce them in volumes of 100+. Otherwise it will be about 25% more expensive. Still, not bad for the functionality.

--
Greetings Bertho

[matseng]

Really nice.... Have you considered doing one with a xmega as well? They are much more powerful than the old mega series and about the same price (and dropping) - but only 3.3 volt devices of course...

[Bertho]

Really nice.... Have you considered doing one with a xmega as well? They are much more powerful than the old mega series and about the same price (and dropping) - but only 3.3 volt devices of course...

I considered the xmega, but I have no experience with them. However, I did use the uc3 (avr32) series and am working on a 32-bit board that would make a good match for powerful. I was thinking AT32UC3B0512.

I'm not worried for 3.3V devices at all. Most signaling nowadays is at 3.3V or lower, so it is only natural to go that route.

[matseng]

I used an XMEGA for my KimCard - I was a bit hesitant at first since it was my first xmega project but it turned out to be really simple to use them with the new i/o remapping features and the other fancy stuff they put in it.

Haven't used the avr32-series yet though... Maybe one day...

[TomKeddie]

Did you consider teensy?

http://www.pjrc.com/teensy/

25/46/34 I/Os, $16/$24/$19 with Arduino support.

[Bertho]

Did you consider teensy?

Yes, and it does not pay off for us to import them. They too are expensive for the functionality provided. The cheapest Arduino is about DKK 200,- here in DK (and then add DKK40..60 to get them shipped to your home).

One of the major points of all these known boards, when imported, is that we have to pay duty on them and that makes them, simply said, not competitive or too expensive. The local pricing is from DKK 150,- upward. For anything that is usable you are looking at DKK 250,-. It certainly does not help that the Danish VAT is 25%.

If you order from China here, and your package is screened in customs, then you are about to receive an additional bill of DKK 150,- from customs. If you are unlucky, and you have something of "estimated" value in the package, then you have to pay even more.

The trick with these boards are that I can make them cheaply in this country and then, at least, the whole EU will have the same pricing. My guess is that US wouldn't be a problem either, but that I cannot be sure of.

Edit: the AvStamp and PicStamp boards can be mailed in a simple (bubble) envelope with standard postage. That reduces the costs here in this country too.

[Bertho]

I used an XMEGA for my KimCard - I was a bit hesitant at first since it was my first xmega project but it turned out to be really simple to use them with the new i/o remapping features and the other fancy stuff they put in it.

I just looked at a few datasheets and it seems to be pretty straight forward indeed. It is certainly worth considering since they are priced competitively too. Now to find out which part to pick. The problem of choice, sigh ;-)

Haven't used the avr32-series yet though... Maybe one day...

I can only say to try. The initial SoC configuration setup is a bit steep to get the hang of, but the rest of the coding is very straight-forward (beware the errata).

[matseng]

[quote="Bertho"I just looked at a few datasheets and it seems to be pretty straight forward indeed. It is certainly worth considering since they are priced competitively too. Now to find out which part to pick. The problem of choice, sigh ;-)[/quote]
Some of the models, for instance xmega32A4, that have USB also have hardware encryption which require an export licence to get them shipped out of USA - atleast to Malaysia. It might be easier to get them to Europe...

[Bertho]

I just looked at a few datasheets and it seems to be pretty straight forward indeed. It is certainly worth considering since they are priced competitively too. Now to find out which part to pick. The problem of choice, sigh ;-)

Some of the models, for instance xmega32A4, that have USB also have hardware encryption which require an export licence to get them shipped out of USA - atleast to Malaysia. It might be easier to get them to Europe...

I can see that Malaysia is not part of the Wassenaar Arrangement (http://www.wassenaar.org/ see cat.5 part 2). That complicates things a lot.

[bearmos]

very nice, bertho. I realize a lot of people like to use established dev boards, but there's something to be said for doing it yourself. Based on your circumstances, this seems to be a great solution for your local hackerspace.

These bread-boardable modules always come in handy and it's super easy for a member to get some help on getting a variant up and running if they decide they'd like to base another board on this one.