the 5v/3.3v shield thing is not a -huge- deal: avr's are (im like 99% sure) 5v compliant so, at worst, it should still work. (if using a r divider, then 1.8V is still higher than most CMOS Vih)
Awesome feedback. Thanks! I am more worried about customers buying Skinny and getting frustrated when it doesn't work with their 5V XBee shield, etc. The ATmega168 should be able to clamp higher voltages without too many problems.
ironically, if you actually solder in female headers to put a shield on it, it will be exactly the same height as a diecimila
The power jack and USB connectors are pretty tall aren't they? And if we're going for pocket-ability, I'm thinking peeps will want to solder in their own wires. The female connectors were a fantastic idea in the beginning. You ever try to desolder a through hold connector like that?
theres no 1k series resistor on RX0, which means if you've got a GPS (or xbee, or xport, etc) connected to rx/tx - many tutorials/examples do this - and the serial link installed (for debugging/uploading) its going to perform very strangely. if its not included, it should be noted
Good point. I will add.
the switch would be 108914981273 times awesomer if it was RA and on the board edge so you could turn it on/off when a shield is on. no big deal tho. (i am rooting for a right angle 3pole switch in the next arduino rev.)
Nuther good one. I will go scrounging.
is the 3.3v on the serial connection an input (to VCCIO) or an output (from the internal miniregulator in the 'RL). if its the latter, thats kinda sketchy. :-/
My designs are always a little sketchy
If it sparks, unplug it. If it heats up, you better check VCC/GND. No really - The 3.3V pin on the male header on skinny is an input. The USB board provides 3.3V. You can have the board 'on' and hook up USB without problems. It's a little sketchy to have two vregs on the 3.3V bus at the same time, but both the FTDI vreg and the on-board SOT-23 mini vreg are both pretty burly when it comes to abuse (misuse).
the fuse seems a bit odd - the diecimila fuse is there to protect the computer's internal usb hub. a reasonable 3.3v regulator (you dont have the part number anywhere so i cant check it) should have short circuit protection.
I like PTCs. If the novice user does anything silly, the fuse takes the brunt. I shorted 3.3V and GND on the board and the PTC kicked right in. The micrel v-reg on skinny is dang impressive though. I hooked up 10, 15, 20, 25V DC and loaded the board with 100mA load. The v-reg did great up to 22V when it started to auto-shut off. I then hooked up 10V, 15V, 20V backwards. The tantalum input cap popped at 20V. Tantalums fail unsafe (shorted VCC to GND with carbon) so I removed the popped cap, attached correct 15V and the board continued to work. I like parts that can stand up to my mistakes. The diode would be good but may cause problems with batteries (~0.5V forward drop).
i dont really get the 8mhz/'lilypad' thing. i use internal oscillators all the time for cheapie kits, but i'd never do it for a project where customers are expecting to use a serial library where they cant tweak the TCCR values (and where the bootloader is pre-burned with a set value that is not calibrated). i've found that the int oscillator does vary a bit over large runs/temp/voltage. why not include (at least) a ceramic oscillator? you can get a skinny one for $0.20, a full-on crystal setup is maybe $0.35 or $0.40
Yea, my bad. I was cutting it a bit thin. Next rev already has tiny 8MHz resonator.
I don't really see any use for this. There several ways to interface an "normal" Arduino to 3.3V peripherals. And since they made a "full-sized" Arduino board anyway, why didn't they use the PDIP-Version of the chip (which can be replaced in case of an "accident").
Cost. None of the components on the Skinny are PTH. It's expensive to solder a DIP package. We figured we could get the price down. Besides, anyone know of the accident/fry rate of the ATmega168? Like zombies, those things are hard to kill.
Thank you again for the review. We'll spin the next rev.