Friday, January 27, 2012


So, you lucky soul, you have a Atmel JTAG ICE Mk II, AVR Dragon, or an AVRISP MkII on the bench.

Can't remember the pinout for the AVRISP port? Or the color codes on the squid cable?

Me either. Here's a reference guide to help you.


Here's the AVRISP pinout diagram for both the 6-pin and 10-pin AVRISP header.

Pinout for Atmel ISP, AVRISP MkII, JTAG ICE Mk II, etc.

28-DIP ATMega

Refer to the following if you're using a 28-DIP ATmega328P, ATmega8, ATmega48, ATmega88, ATmega168, and other 28-pin ATmega AVR microcontrollers (check the datasheet).

ATtiny2313 AVRISP pinout

ATtiny2313, 4313

This diagram shows AVRISP pinout diagram for programming ATtiny2313, ATtiny2313A, ATtiny4313 AVR microcontrollers.

ATtiny84 AVRISP pinout

ATtiny85, ATtiny13

Here's a pinout diagram for an 8-DIP ATtiny11, ATtiny12, ATtiny13, ATtiny13A, ATtiny25, ATtiny45, ATtiny85:

ATtiny13, ATtiny85 AVRISP Pinout

eeZee Tiny Breakout Boards

eeZee Tiny makes it easy to prototype and program your ATtiny

My eeZee Tiny breakout boards include AVR ISP headers so you don't have to remember the pinouts above. They're low cost and available from my store on Tindie.

If you think others might benefit from this article, could you do me a favor and share it? Thanks!


Friday, January 20, 2012

Encoder Board Evolution

The old encoder board I fabbed for Data Bus has failed. Rather than repairing several lifted traces on the old one, I felt that a more reliable approach was to order a professionally fabbed board via OSH Park.

I took the opportunity to redesign using SMT components so I could shrink the board.

Old board above, new SMT board below
The old design was based on an LM393 dual comparator IC configured as a schmitt trigger. So is the new board, but instead of a single IC, it was easier to route traces using individual, Texas Instruments TL331, SOT-23 comparators. All the passives are 0603 size and the LEDs are 1206 size.

I'm still working on my technique for hand soldering SMT. Here are some things that seem to work so far:
  • Push components out of their tape using the point of a small nail
  • Tin the pads then suck off the solder with solder braid
  • Use a flux pen on all the pads
  • Use a really small tip and a decent iron
  • Use 0.015" solder; I use Radio Shack silver bearing solder
  • Use non-magnetic pliers/tweezers to pick and place parts
  • Use the nail tip to gently nudge them around on the board
  • Hold the parts down with the head of the nail while you solder
  • Tack down one side of the component, add solder if needed
  • Then add solder to the opposite side while holding it
Components tend to get pulled vertical by solder surface tension if you have too much solder on the pads so that's why it seems to work better to remove some solder and to hold the component down with a nail.

It's pretty darned tedious. I ended up reflowing the SOT-23 comparators using my reflow skillet. As I have two encoder boards to populate, I will try reflowing all the parts on one of them and see if that is any easier.

Hopefully the new board will hold up better to the rigors of testing and competition than the home fabricated board. Plus, I'll have spare boards in case something goes awry.

Friday, January 13, 2012

Geek Destinations: JB Saunders

I had some time off during winter and I had a free day all to myself so I headed up to Boulder to meet a friend and visit JB Saunders. This place should be on every geek's bucket list. Holy cow...

Saturday, January 7, 2012

AVC 2012: On The Waiting List

Crap! I'm on the "backorder list" for the 2012 Sparkfun AVC!

That means several people have to officially drop out or I won't get to compete at all this year! I didn't see the announcement until a day after and apparently, by that time, all 50 slots had already been filled. I am in the top five on the waiting list, though, so there is still a glimmer of hope.

I don't know if I will get to compete but what is certain is that Data Bus development will continue and you'll read about it here.

Equally certain is that I will be hoping and praying that at least 5 other contestants fail miserably and give up... (is that wrong of me?)

Friday, January 6, 2012

LPCXpresso Surgery

I have an LPCXpresso now. The board breaks out a 120MHz LPC1769 to DIP form. Attached to the board is an LPC-Link, a JTAG debugger. To use both boards conveniently, they need to be separated. One of my readers, Nemo, suggests an Xacto hobby saw and mitre box to split the boards apart. He achieved very nice, precision cuts this way.

My approach for cutting apart the LPCXpresso and LPC-Link involved use of a plastic cutter and utility knife shown above.
  • Use solder braid to remove the solder from the solder jumpers between both board halves.
  • Then score a line with plastic cutter on both sides using straight edge and (gently) vise. 
  • Score until you can't easily go deeper. 
  • Continue scoring with the narrower utility knife to score a bit deeper
  • Snap the board in half by hand without much effort. 
  • Sand both edges.
Now mount male header pins on one side, female header socket on the other, et voila. Plus, no cables to deal with.