Yes, both Farnell and RS are the best options in Europe, and RS even provide a special website for hobbyists with VAT included (at least in France). I do not totally agree with your remark on their higher price: if you count in taxes and shipment, they are not far from what you get with Farnell in the end. I would say they complement.
Please understand that I do not complain against DK (apart from their limited carrier choice), the problem is with UPS and probably other international parcel services charging ridiculous amounts for electronic paperwork: at this tag point, this is just a hidden margin unrelated to the actual performance or real item value.
I fear that by using Mouser or any other US-based distributors, I fall into the same trap, as they probably use the same parcel services for worldwide delivery.
It's nice to get a feedback and see you really had fun soldering it!
Yes it is not for the faint-hearted, as there are some 0603 parts to solder, but nothing impossible with a soldering iron, like BGA or QFN chips. The fine pitch LPC chip is actually pretty easy to soldering using the "tack & reflow" technique with a flux pen.
The strange USB connector is coming from an old SparkFun EagleCad library I had, where a Hirose connector was used with pretty unusual position pins.
FYI, I set up the list of parts with the references both at Digi-Key and Farnell: it is in the github repository.
Yes, ordering from DigiKey in Europe really hurts, not because of the item price or shipping (it is free over 65 EUR), but because of the carrier that s....: the only option is to use UPS, which charges 34 EUR for a ridiculous "customs processing fee": they have strictly nothing to do, since DK already declared the custom code for each individual part! And these jerks are stupid enough to send the invoice directly to the business account corresponding to the shipping address (my company) instead of my home billing address, as it was specified! It was only after 2 invoices unsuccessfully sent to my company that they retrieved the correct address, and sent me a very bad letter with threats of bailiff... I paid them, of course, plus extra interests: 45.63 + 3.65 = 49.28 EUR to UPS, 9.72 EUR to Customs and 75.33 EUR to DK: 37% UPS, 7% Customs, 56% DK...
I wish DK had warehouses within the EEC, or they could provide another cheaper and less stupid carrier (like USPS) as an option.
The cheapest integrated solution I have found is using a FAN5331: $0.97 @ DK. But then, you need a 10 µH ferrite inductor with a 1 A saturation voltage ($0.78) a BAT54 diode ($0.16) and a 4.7 µF 16 V ceramic capacitor ($0.34), so we reach your $2-$3 limit...
Electronically, your proposal is nice, but I don't know how the CS pin is driven from the kernel driver: it may be at the lowest level by the SPI controller itself, or worse: this may not involve the CPU altogether but only the DMA engine...
Ok, I will let you know, I just did some simple tests up to now.
Regarding Bitlash, it may be a little too big to fit in the LittleWire (considering the USB stack), but if you look at the code, there are some #defines for the ATTINY85.
Maybe the idea of an embedded interpreter is not applicable to it, but the language syntax is nice and easy. It could be ported onto the host side, the ATtiny only executing pre-parsed intermediate bytecodes...
Sorry, I can't help you with he pic24f, I don't use them.
So far, I tested my perf-board LittleWire for AVR programming, I2C DS1307 and USB-CDC.
BTW, do you know Bitlash? It is an open source interpreted language for the Arduino, but it can also be compiled (with restricted features) for the ATtiny85. Maybe it is something to explore for the LittleWire?
As I was not one of the lucky persons to win a LittleWire, and that I had all the components available, I decided to build my own version... on perf board! [attachment=3] Doesn't look too bad from above, but...
... below it is a little but messier: as it is not strip board, you have to "bridge" all the pads with solder to create traces: [attachment=2] I was able to avoid wires, except for 4 of them (2 are a consequence of the funny ISP connector pinout).
I separated the 2 capacitors to have one close to the USB connector, the other one close to the ATtiny85.
I decided to put the jumper on the same R/A header, here is why: [attachment=1]
I found this RX2KL05/S-5 Camden/Boss enclosure to be almost the perfect size for this baby: [attachment=0]
The enclosure is available at RadioSpares (unfortunately no longer at Farnell). With a little cutter knife carving, it is a nice protection for this LittleWire derivative!
Needless to say, it is fully functional and once the ATtiny85 flashed with my BusPirate, it is working as expected!
Maybe this case could be used for the original LittleWire too?