Evolution of a Board

Metaboard Redux Work

I have been working on my Metaboard Redux and it has been quite a challenge building a board that works well using the USBASP bootloader.  The primary challenge is handling the conflicts that arise from using digital pins 2 and 4.  Many shields will assume one or the other (or both) to be free.  There are two problems with this...

The first problem is that circuitry on a shield that uses pins 2 or 4 may cause communication issues, so before the device can be programmed, either the shield needs to be removed or anything using pins 2 or 4 should be disconnected.

The second problem is that the V-USB circuitry may cause the shield to fail because it is active even when there is no communications taking place.  This is a serious problem.  The Seeed Studios Relay Shield is one example of a shield that is incompatible with the normal Metaboard.

So to solve this problem, I am including a latching double-pole, double throw switch that can swap the two lines between the V-USB circuit and the two pin header slots.

While this makes for a simple solution, the wiring layout becomes more difficult.  It basically boils down to 4 jumpers that need to be added to break into the lines.

Coupled with the difficulty of the connections, I also had to place the switch outside of the area that would be covered by a shield.

The Right-Handed Arduino

If you were observant, you would have noticed the odd placement of the communication and power circuitry on the right side as opposed to the standard left.  I have decided that using the standard left-sided format is not the best placement for the Metaboard because of the need to access the programming jumper, the reset button and now the data line switch.  On the left side this pretty much means you have to remove any shield in order to program the device.  While in the long run this is not a show-stopping problem, you just have to keep removing and replacing the shield for each iteration.  With the right-sided solution and the data line switch, there is no longer a need to manually disconnect anything to re-program the device.

Miscellaneous

A couple of notes...

• There are no mounting holes
• Optional features
• ICSP header
• D13 LED
• Power LED
• Power Circuit