Tons of IO project is comming together

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andrewpro

New Member
I've finished one of the digital IO boards for my project and have posted it on my website if anyone is interested. It's got 64 bidirectional IO's interfaced through I2C.

<A href='http://www.plistin.com/research/picaxe/Digitalio.html' Target=_Blank>External Web Link</a>

I've also finished one of the analog multiplexer boards, and I'll write up a page on that as well and get it posted soon. Feedback is appreciated.

--Andy P

Edited by - andypro on 8/13/2005 11:43:55 PM

Edited by - andypro on 8/14/2005 12:42:15 AM
 
A

andrewpro

New Member
Well, I got the page for the multiplexer board done. You can see it here:

<A href='http://www.plistin.com/research/picaxe/Analogio.html ' Target=_Blank>External Web Link</a>

It's also linked to on the digital board page in the text at the top.

As for the headers, they're non-keyed for a reason. Eventually I'm going to make a daughter board for it that will have more robust connections for the cables. What kind of connections and cables I dont yet know, probably some sort of Dsub or waterproof round connector. That's why the headers are offset like they are and not symetrical with each other...so that you cant put the daughter board on backwards.

I didn't mention it in the text as of yet for two reasons:

1) I havn't decided if I'm going to do it with this board, or wait for the next version I make with an etched PCB, but the possibility is designed in so that if I do decide to do it now I can.

2) I just wanted to start getting the project up on the web as per some peoples requests, and thought I'd put it up here on rev-eds board too. The page is a work in progress, and I will be elaborating on some aspects (possibly those I havn't thought of yet) as time goes on, changing layout, getting better pics, etc.

--Andy P
 
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Chris DeHut

Senior Member
Thanks for update Andy, I will be keeping an eye on that page as I am just getting started with my project which is very similar.

Chris
 
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Chris DeHut

Senior Member
Andy,

By chance do you know if this circuit will work with overclocking the PICAXE?

I need a little more speed than what I am getting so far based on my preliminary tests. Overclocking to a 16 Mhz seems needed at this point.

Chris
 
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Chris DeHut

Senior Member
Also,

by chance do you know how long it takes to scan all 64 ports? Knowing that will help me a lot with my design before I get too far down the wrong path.

TIA
Chris
 
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andrewpro

New Member
There are I2C keywords for overclocking. The speed setting in the I2Cslave command can be i2cfast for 4 mhz, i2cfast8 for 8 mhz, and i2cfast16 for 16mhz. So, for overclocking at 16mhz:

i2cslave %0100xxx0, i2cfast16, i2cbyte

Replace the X's with your chip addresses. I've done it at 8mhz, and it works fine. I dont see why it wouldn't work at 16 mhz.

I havn't measured the exact speed it takes to read all the chips, but mathematically it could range from about 750 microseconds to a few miliseconds depending on how fast your running the picaxe. It also depends alot on exactly what you do with the data as it comes in, and what you do wih it after it comes in. I'll see if I can get some definitive numbers on jsut the raw read and store for you either later tonight or tomorrow.

--Andy P
 
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Chris DeHut

Senior Member
Thanks Andy,

If I could trouble you for a bit more too.

As I am not only learning the PIC side of this, I am also learning the electronics. Do you have a schematic of your &quot;Tons of I/O&quot; project? I am stumbling on a couple of issues and in hopes of learning more, I would prefer to look at a schematic as opposed to the easy way out and simply ask/get the answer.

Thanks again!

Chris
 
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tarzan

Senior Member
MAX7300 &amp; MAX6956 PCBs i2c 20x I/O ports <A href='http://groups.msn.com/picaxe/max7300ampmax6956.msnw?Page=1' Target=_Blank>External Web Link</a>
 
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