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New board/shield


#1

While waiting for the Panda’s, the PCB from the manufacturer and the components from Sparkfun, I’m creating another board for a (long term) personnal project.

Here are its actual specs :

  • precision drive 1 or 2 bipolar steppers
  • have many digital IO’s
  • have many analog inputs
  • have as much relays as possible, including SSR relays
  • link to a computer via the network for data acquisition
  • leave as much free pins as possible in the shield header, so that other shields can still be used

For the steppers, after some trials, I finally decided to use the EasyDriver board directly on mine. This way, you can put 1 or 2 boards, or even none if you don’t need it…
Here, I’m using 4/8 pins from the UExt connector.

For the digital IOs, it’s almost the same thing as the board sold here at GHI. I2C permits the use of only 2 pins for 40 IOs.

For the analog inputs, I’ve chosen a ADS7830 that offers 8 channels at 8 bits precision. I don’t know if 8 bit is really enough though :think:
This chip is also driven by I2C, so no pins used.

For the relays, I will have to choose smaller ones, I think. I didn’t have time yet for this. The SSR are too big, I think. I know that DIP6 relays exist, so I will try to find them.
These will be connected to the extra-IOs I get with the PCA9505, so again : no shield pin used. They are not yet connected on the prototype below.

For the Ethernet connection, a Moxa 4100T can be put in the middle of the board. This one eats the COM1 pins, though :frowning:

So, if I summarize with a complete board (2 steppers and the Moxa), that’s :

  • 2 stepper = 8 UExt pins
  • Moxa = 2 shield pins (COM1)

All other shield pins are available. I think this is good. Even though no COM port is available because the Moxa is used for communications between PC and board.

What do you think of this ?


#2

what base controller board are you assuming? If you went Panda, you could get soooo many more IOs :slight_smile: Plus you could use a WIZ811/812 module for the network piece and get GHI’s supported ethernet socket networking (uses an SPI por plus some other general IO). In fact, I’d still suggest doing that since it makes things freakin ezy.


#3

Make sure you call the polygons ground (looks like you have) and then manually add via’s into the “holes” which your trace’s have created with the same name as the ground net. This will fill those gaps up with groundplane. You probably also want to liberally sprinkle ground vias around, especially near signal lines.


#4

@ Brett : I’m assuming either Panda or Domino (or Arduino). But you’re right : in case of Panda, that would make more IOs than needed.
About the network controller : you can still add this shield on top of this board, that’s why I didn’t use it. The real use of the RJ45 connector is in conjunction with the Moxa board, that will do all what the Wiznet does plus offering a virtual COM port on the PC to communicate with the board via the network.
The Moxa is not mandatory and/or not needed if you use a network shield, though.

@ MarkH : I will do what you suggest about vias and ground plane.

What is the purpose of your second proposition ? Reduce noise ?


#5

correct :slight_smile: cuts down on noie and reduced interference.


#6

I don’t know how to do this :frowning:

I can put a via in the middle of an “empty” area (empty on top copper and ground on bottom copper) then assign the “gnd” net to the via, but I don’t know what to do after that :wall:
Autorouter does not put a ground plane on top copper (where it should go) and I don’t know how to manually do the same action. Any help would be welcome, here :think:


#7

Just found out how to do it. No need for an answer anymore.


#8

Your board looks really good!
It took you only a few days to build this board from zero, isn’t it?
:clap:


#9

Yes, indeed. But I don’t know if it’s correct “electronically speaking”, though…

This is all about reading datasheets, Eagle docs & forum, Google and personnal time ???

Anyway, since I don’t have anything yet to play with (FEZ board(s), components and PCB, all are expected to be shipped at some time), I will stop speaking until I can show something real. :hand:
If someone wants to contact me in the meantime, please use my email address on this page.

Thank you for your interest. Bye all.