Revised P2 PLC (Concept)
Rayman
Posts: 16,098
Currently have a Bud DMB-4775 enclosure based PLC going with P2 SWaP module. This is all fine, but not entirely happy with some things, mostly the way have to carve the enclosure. Also, the SWaP module is kind of a pain to assemble...
So, now looking at the slightly larger DMB-4773 Bud enclosure. With this one, and some rearranging, just have to carve the upper part of the enclosure and then can cover it up nicely with a 3D printed cover.
The Amphenol modular connector is moved up by putting it on a separate board. This is probably a good idea anyway, in case another project wants a different connector or no connector at all...
The other big change looking at is possibly replacing SWaP with what am calling "P2 Core" module.
This is now 1.6" square with castellated edges and also 0.05" pitch headers, so can be soldered to board or connected using headers. Looking at 20-pin headers on all four sides. Think that should be enough...
The P2 Core module is a proven design with 4 layers and can be well overclocked. It also has a regulator for VDD on each group of 8 pins, so is better for analog signals. But, the main thing is that it is much easier to assemble than SWaP...
Comments
There's a lot more flexibility here... Could still use SWaP on main board if wanted, could be better for some things...
Really like the idea of putting that modular connector on a separate board, so can be exchanged for something else or just not used at all.
I previous arrangement the large bottom board needed a cut out to accommodate the modular connector, but here the top board will need a cut out.
This may be better as the top board isn't maybe as important...
In fact, if leaving the top cover in place, don't even need the small top board...
Nice thing with either SWaP or P2 Core is that these other boards can be simple 2-layer designs, easily customizable...
Do you already have some feature list of what interfaces or applications you are planning to support?
The connector module has Ethernet, USB-A, USB-C... but what are the two connectors at the bottom?
@ManAtWork Good questions... The two on the bottom are just plain RJ45. Planning on connecting them with 5V, GND, and 4 P2 I/O in the way @refaQtor suggested, as a simple way of connecting to external interfaces...
The Ethernet is going to go to a header on main PCB. One would need to connect something to this header to make the port useful. It could be a simple passive thing to just provide a third RJ45, or it could be a Wiznet device for ethernet.
The USB-C is for serial interface with optional power and/or programming.
The USB-A would go to ESD chip and then to P2 for keyboard, mouse, etc. support.
So, this all goes on the main board. The revised plan is to have that modular connector attach to the main board with 1 or 2 headers, so it can be at the right vertical height.
But, one could also just not use the modular connector board and thereby have more I/O connectors on the bottom board.
I'm not 100 % sure yet that this is going to work out physically, but looks good in SolidWorks, so am hopeful.
The other new plan for the main board is to have all the connectors to the bottom board be the 12-pin Eval style arrangement.
Will use IDC cable to connect middle (main) board to bottom board with the I/O and power supply.
This has the advantage of being able to play around with Eval style accessories as well, before installing into enclose anyway.
Also, this would let the bottom board be connected to other Eval style P2 boards for testing.
Just seems like adds some flexibility...
Guess the idea is that the main (middle) board can be flexible enough to be used for most applications, while the top and bottom boards are application specific.
The top board is not really even needed, could just not use it and leave the DMB-4773 top cover in place.
But, I'll probably do one with small LCD and some buttons, and 3D printed bezel on top of that.
Might use the clear plastic cover on top of that with holes for the buttons, not sure yet...
The bottom board is more of a challenge. This is where the real interface to other things goes...
If main goal was to sell a bunch, maybe I'd copy the Arduino PLC thing and have some 10A relay outputs there so could turn on lights or small motors or something.
But, I'm more interested in plain 24 VDC Digital I/O, so will probably just do a bunch of that...
Almost have the "P2 Core Module" design done. Just need to connect through hole I/O to vias to be castellated...
Passes design rule check already.
This seemed to be almost too easy... Somethings that means there's a horrible mistake...
Think will use OSHPark to get a quick first try.
I'm liking them for price and speed and guess can live with purple pcb for prototypes...
Made some quick decisions as to where to put power and I/O on the headers...
Doesn't need to be final, but might be.
The thing about power and GND in this particular case is that it doesn't matter all that much...
The 1.8 V VDD all goes through one trace to a fill that goes all the way around under the P2 chip on the top plane and is well bypassed by the 0402 caps right next to VDD pins.
The VIO actually goes first to regulators, one for every 8 pins, that is also well bypassed.
So, where the actual power pins are doesn't matter so much.
For convenience, the 1.8V ones are all close together and close that trace that brings it to the P2...