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 Post subject: First Board - Atom Module To Dev Board Adapter
PostPosted: Sat Aug 21, 2010 1:13 am 

Joined: Mon Aug 18, 2008 1:26 am
Posts: 799
Location: CA bay Area
I did a thread here earlier under the Nano section about using the Nano parts on one of those large PIC development boards, the EasyPIC3 and -4. That's straightforward, but using the BasicMicro modules isn't. The module pinouts don't match any PIC pinouts. I wanted to be able to use all those resources of this dev board with modules, so I decided to make an adapter board that would make this possible.
I also wanted to be able to learn how to use software to make a schematic and layout a board. There are places on the web that supply free software to do just that, and then they take the finished files and fabricate the boards for a fee. The place I chose, and the name of their free software, is ExpressPCB. This comes in two parts: a schematics program, and a board layout software. After you create the schematic, you can use that file to assist in laying out the board. This package can be found for investigation and download at:
I can't recommend this software package for any but the most elemental designs. I have used 18 year old schematics software with more capabilities. But, it is more than adequate for the job at hand. I have no prior experience with board layout software, other than watching others do this and talking to them about basic considerations.
The main reason I picked ExPCB was because they discussed their board fab fees up front and I found them reasonable. They have four services, and therefor four basic rates. I picked the Mini Board Pro service, with two day shipping. This restricts the user to a 3.8 inch by 2.5 inch board. This gets you a professional board, complete with plating, plated vias (allows connections from top to bottom of board), solder mask and one-sided silkscreen. This came to $91, with two day shipping. Since this service automatically produces three boards, the cost per board was very nearly $30. Not bad for a commercial-quality proto-quantity board that size.

What I needed on the board was:
1. Two module sockets, a forty pin DIP for 24-, 28- and 40-pin modules, and a 14-pin SIP for the ProOne
2. A power jack to bring in power with for standalone operation (no dev board)
3. Four ten-pin headers (2x5) to connect cables to. These were for ports A, B, C and D.
4. A power-on LED
5. A serial connector to allow programming (DB-9)
6. A reset switch
7. A few peripherals to experiment with, if no dev board was immediately available
- two switches
- a users' LED
- three headers for servo motors
- an undedicated 8-pin socket for EEPROMs (I2C and SPI), with pullups on seven pins.
- a socket for an IR sensor
- a socket for a one-wire IC, like a DS1820 thermometer IC
- a 10K potentiometer
This list also includes the miscellaneous capacitors and single-pin connectors to allow connections between all this stuff!
Having just a power jack and no regulator means you must use a fully regulated AD/DC wall adapter for the 5V!I used an AC/DC power supply from a 1.1 USB hub. 5V, 2 Amps, fully regulated!

I tried the board with 40-pin modules, both BasicATOM and Pro, and the ProOne. I did my first experiments on just the adapter itself. In no time (good old Studio!) I had three servo motors humming away, the LED doing stuff based on switch closures, and the serial terminal reporting ADC values as I changed the potentiometer!
Then I connected the adapter to a Mikroelectronica easyPIC4 Develeopment Board and started exercising 32 LEDs and the 7-segment displays. Swe-eet! Then I put "Hello World!" on the EZPIC's LCD and called it good enough.

I did another board after this, a "mini-dev board", along the lines of the EZPIC board, but seriously restrained by the 3.8" by 2.5" limitation. This had an LCD port, stepper motor port, more LEDs, switches, and pots. Just something to use if table space was limited. It tested out OK also. I have no pictures of this here. Maybe later.
I still haven't tested everything on both boards, but the main idea was realized.

My final schematic for this board looks like:
EZPIC2ATOM schem.PNG [ 54.31 KiB | Viewed 2639 times ]

I took the final schematic file and used it to produce the board layout:
EZPIC2ATOM layout.PNG [ 46.34 KiB | Viewed 2639 times ]

And the final product looks like:
Adapter Complete_051510B.jpg
Adapter Complete_051510B.jpg [ 392.92 KiB | Viewed 2639 times ]

Adapter In Use.png
Adapter In Use.png [ 896.66 KiB | Viewed 2639 times ]

As you can see from the last picture, I have only the bare essentials installed on the adapter for initial testing. That is, a 40-pin socket and the serial connector, and a bypass capacitor. I got power and resources from the development board alone.


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