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USBmicroISP Part 2

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Intro

Continuing to document my USBmicroISP, based off the USBtinyISP from Adafruit, here is my the assembly process. My first post detailed the why I'm building this version, and its features.  Essentially I wanted to make it with a smaller, nicer looking enclosure and have it use a micro USB cable, not a printer USB cable.  I used much the same schematic.

Assembled USBmicroISP; green means ready for programming!

Parts Received

I often buy the parts FIRST, then check that I designed the board correctly by printing it out 1:1. Lining up the new, often-weird parts (the ATTiny, the XTAL, the MicroMatch connectors) made me realize I needed to rearrange the way the connectors go out of the case:

Finished product.  Tight quarters in this case!
Having finally received the PCBs reminds me again how amazing OSHPark is:

Nicely fabricated OSHPark boards.  Notice the ATTiny IC1 is on the top layer, and the buffer IC2 is on the bottom layer.

Build Process

Having received the 3 boards from OSHPark, now I can cut out the required slots in the blue case, and populate the board.

Need one slot for the micro USB connector.
Micro USB is about 0.1" in height.  Using this, I could cut the slot.
Slot cut into plastic for the USB connector.
Lines up with pads, and centered with enclosure.
The dimensions for the USB slot are on this file, as I calculated it.  It was pretty easy; just take into account the height of the built-in standoffs of the enclosure, then the thickness of the board.  Having extra boards for this part was a great help, as the populated one doesn't fit until you cut out the USB slot.

I didn't have the required #2 x 3/16" board screws, so I cheated and used some longer ones with cut tubing to bump them out a bit:

Board screws too long?  Not to fear.
Then I needed to cut/file out the slot for the 2 cables, the 6-pin and the 10-pin.  I didn't make this a slot, but a notch in the base and in the lid.

Notches in the base and lid for the programming cables.
I thought about cutting holes in the lid for the 2 LEDs, but thought if I didn't it would keep the dirt and dust out.  Plus, the translucent case lets the red and green lights through just fine. :)

Could have raised the LEDs up through the lid, but thought better of it.

Programming Firmware

Programming the ATTiny with firmware needs to be done before it will work.  As I mentioned in the 1st post, this can be done by carefully soldering a couple wires to the pads of the ATTiny and using another ISP, Arduino Uno or Mega. There's a couple guides out there, like this one. You need to burn the firmware gotten from here.

Plugging in the micro USB from a computer after a successful burn will yield a green LED:

Ready to program any and everything!
If you have trouble, try re-burning the firmware, make sure you have the correct USB drivers for the ISP installed, and the latest Arduino software installed.

Usage

Usage isn't any different than the other ISPs.  JP3, when installed, uses the 5V USB to power the target.  Make sure to REMOVE JP3 when you're programming a 3.3V Atmel!  (has to be self-powered, of course)

GREEN is to indicate power.  RED is to indicate data transmission, the device is busy.

Credits

Credits to Adafruit for the original design, and anything they based their design on.  I have recently found a few other ISPs out there:

https://www.tindie.com/products/nsayer/micro-avr-isp/

~JWilly

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