Reasons for Arduino pin layout


Is there a reason for the Arduino (Uno) having it's expansion connectors not in 100-mil grid?

Until a few days I tought it would even be possible to plug the long-pin version into a breadboard.

I usually rather do PIC stuff and create my own PCB's. But for playing around I used an Arduino. Now I wanted to make my circuit a little more permanent than in a breadboard (just wired with cables). But when trying to align a velo board I noticed that the two pin rows are in a 50 mil grid and that the PORT D pins (pins 0-7) are also 50mil off-spaced to the connector for pins 8-13 (+SDA,SCL)

Is there a reason for the decision to place those connectors off a 100mil grid?

It just robbed me some fun I couldn't just right start into it but first have to order those proto-shields. Altough they are not really expensive, about 4 € at RS components. It's just that an electronics enthusiast has most probably some velo-boards laying around here and there :slight_smile:


Probably, it was just a mistake.

There are some workarounds using bent headers etc that allow the use of standard stripboard.

I heard it is because there was a mistake with the layout with the first boards that never got fixed, because all the shields have the incorrect spacing and they can't change now. But why it wasn't fixed in the second batch, ask Massimo Banzi!

I guess I will make an adaptor shield :slight_smile:

Then the form-factor would be bigger so maybe it doesn't fit into some casings. But the adaptor shield would anyway just make sense to allow connecting a quick vero-board prototype.

There are special bent headers that are made especially for making Arduino shields out of perfboard. They are slightly more expensive, and you can always make your own with long male-female headers.