Using the P2 Edge with breadboards

Dave Hein

I do most of my tinkering with solderless breadboards. I wanted to use the P2 Edge and the accessory boards with a breadboard, so I developed a couple of adapters to make it work. The P2DIP44 brings out 38 I/O pins to two 22-pin headers with 0.1" pin spacing. The two headers are spaced 0.6" apart. GND, RESn, P64 and P63 are grouped together so that a Prop Plug can directly interface with it. Four of the 3.3V outputs that correspond to four groups of eight I/O pins are also brought out to the headers.

The other board is the AccAdapt that is used to adapt the 0.1" spacing of the accessory board connector to a 0.3" spacing so that it can plug into a breadboard. This is a simple PCB that consists of 4 rows of 6 pins each with the first row connected to the second, and the third row connected to the fourth. I've tried it out with the AV accessory board, and it works great.

I have quite a few extra boards if anyone is interested in getting some. It cost about the same to make 30 boards as it did to make one. Send me a PM if you want some.

Ken Gracey

This is great, Dave. If you'd like me to feature this on the Parallax site with links to your e-mail, please send me one.

Thanks, Ken Gracey

PropGuy2

I have been under the weather and with the Holidays being at the top of my list. But the adapter PCB schematics have the rows reversed for the thru hole and right angle connectors. They can also use improvement on the T/H connector routing to the outside pin rows.

The right angle adapter PCB needs to be completely reworked (not yet available as far as I can tell) The biggest issue is that the R/A connector pins spacing is completely different from the standard straight thru-hole connector.

Nice to have besides an actual PCB adapter, would be a layout template (a Macro) that anyone can drop in place when they are designing their own custom PCB board. Working on it...

Dave Hein

@PropGuy2 , what do you mean by "the rows reversed for the thru hole and right angle connectors"? Are you referring to the straight connector versus the right angle connector? I believe the pins are in the same order. However, the right angle connector uses a spacing of 0.075" between the rows instead of 0.1".

I'm not sure that a right angle PCB adapter is practical. It takes up a lot of space. I did a layout, and the PCB is 34mm by 58mm. With the P2 Edge plugged in its around 58mm by 58mm. A dual DIL version of the P2 Edge would be better.

EDIT: If an adapter PCB isn't used the footprint of the connector plus the P2 Edge is about 58mm by 50mm. The clearance below the P2 Edge is about 3mm, so it's possible to place low-profile components on the PCB below the P2 Edge. If the components are taller than 3mm then an adapter board is needed to provide more clearance.

PropGuy2

Here are the PDF files that show the discrepancy in the pinouts - Note the PCB traces do not align with the pin labels

Dave Hein

It looks like the header pinouts have been fixed in the latest documentation. The even I/O pins are now on the outer rows.

JRetSapDoog

Dave Hein wrote: »

Are you referring to the straight connector versus the right angle connector? I believe the pins are in the same order. However, the right angle connector uses a spacing of 0.075" between the rows instead of 0.1".

Thanks for pointing this out, Dave Hein. I did a PCB layout that I originally intended for the right angle connector (with the 0.075" row spacing) but then decided to switch to the straight connector. And I didn't fully realize that there was a difference between the two connectors until now (despite the warning in the posted documentation). So I'll need to redo both my component footprint and board to work with the 0.1" row spacing.

Although the .lib DipTrace file that Parallax posted apparently needs to be opened in a newer version than I am using (I'm still on ver. 2.4), the .pdf that they posted does show a 0.1" (2.54 mm) row spacing for the straight connector. And your post confirmed it for me. Actually, I've ordered both kinds of connectors from Parallax (along with the P2 Edge), but my order is apparently stuck at the airport/Customs in my country (for 10 days now, likely due to a holiday backlog and/or Covid-19). Anyway, I'm glad that I didn't send my board out for mfg. Thanks again for clarifying the difference between the two connectors.