Ever wonder why?

[cncmachineguy]

There have been many many things in my life that I had to wonder - why? But one that keeps coming back is no matter how big the device is, it is still 1 or 2 pins short? Why? Currently I am using the biggest device I can find in the 8 bit world 100 pins. I don't want the latency of port expanders so I am using some buffers to double up on some inputs. Yet still I found myself looking for a way to simply add an led.

I resolved the lack of I/O, but just have to wonder -WHY?

[Charles Linquis]

I have the same issue. I solve it most of the time by having an expansion header on most of my boards. It brings up power, the second I2C port/SPI port, the second TX/RX and PORTB.1, PORTB.6, PORTB.7 and MCLR.

I use one 7 pin connector to connect my ICD3. PGC and PGD from each of the chips goes through a 1K resistor before going to the programming header.
There are 2 (sometimes 3) MCLR connections on the 7 pin header (one for each chip), and a multi-position switch on the ICD3 cable switches one line between the MCLR of chip 1 and the MCLR of chip 2 (and possibly, chip 3).

One connection can program all the chips sequentially (of course, you have to manually toggle the MCLR switch).

I have boards that have 3 8723's! Plenty of pins!

[Jerson]

My answer : Guess the chip manufacturers have conspired to get us for the last pin :))

[Charles Linquis]

Bert,I thought I was about the only one here using so many pins. This makes me wonder what you are up to. What are you building that takes so much I/O?

[rsocor01]

This makes me wonder what you are up to. What are you building that takes so much I/O?

Yes, what are you building? Some kind of space craft? :D PICs with 100 pins have from 70 to 85 I/O pins, more than enough for most projects.

[cncmachineguy]

@ Jerson, I agree completly!!

Short answer - machine controller

The project is an interface between PC parallel port and up to 10 axis of stepper/servos with 2 inputs per axis for limit/home switches. Also a couple of relays for some high power stuff.

So the parallel port itself uses 12 pins, then each axis is 5 pins. so thats 62 right there. I have run out so I must have forgot some things.
It will use 2 50 pin connectors to plug into 2 5 axis cards and carry all the needed stuff to them. Full digital setup for the stepper drives on these cards.

[kellyseye]

That's why some clever so and so invented 'multiplexing'.....

[mister_e]

Agree, but sometimes, multiplexing is not a solution while I/O expander are.

Conspiracy I tell you :D

[Demon]

This is one project I have on the back-burner as well.

But I would go a different route. Each axis does the same processing, so I would use one board (PIC) per axis. In theory it would be more efficient and would not need 100 pin PICs. Same with the limits switches, I'd put that on a separate board.

I just find it easier to work in a modular fashion. It must be the mainframe programmer in me (COBOL). :)


OH DARN! I just checked Mach's site for fun:


32-bit version of Windows 2000, Windows XP, Windows Vista, or Windows 7 Operating System (64-bit will not work)
http://www.machsupport.com/


WOW! Gecko sure has grown since I last saw them!
http://www.geckodrive.com/


(Mach and Gecko drives were my first idea for a home CNC system)

Robert

[cncmachineguy]

Do yourself a huge Favor and at least read around the EMC2 forum. It is Truely the better tool. I look at it like this: Mach is like BS2, gets you up and started, but then you are finished. Thats an important thing, but I like to have a bit more power.

I am fairly certain Mach can not run my 6 axis machine, but I could be wrong. With emc2 I can slave drives and run them independently at will.

As for the modular approach, I started out that way, but when I was about to add a third parallel port just to get 17 more I/O, I decided it was time to use the port as it should be, to pass bytes of data, not single pins of I/O. Then you start to think about comms, how to interface all these modules? The updates are coming every 30uS to be able to reach 1500ipm with my setup (1000 steps per inch). So not a lot of time for talking to each module.

Gecko is hands down top shelf drives. but they themselves will tell you in low current (<4 amp) steppers, they are not much better then a linear drive. But I will never try to talk anyone out of them, they are and deserve to be called - TOP SHELF! On the other hand, in my 6 axis machine, there are actually 7 steppers, 1 axis is dual driven. so thats a lot of cash for the geckos when I can build a unipolor drive that is way happy to run from my ATX 12V power supply for ~ $15 USD each. So my entire bank of drives is the same as 1 gecko.

[Demon]

Thanks Bert, I didn't know about EMC2.

Now the hard part is remembering this when I start my CNC project this winter (assuming I insolate the batcave before spring gets here :D ).

I'm really curious to see pics of your setup; diagrams, hardware specs, anything.

Robert

[cncmachineguy]

LOL Robert just throw it out - "hey Bert, whats that software?" Get the insulation up!!!!

I have been promising PIC for almost a year. Changes keep being made, but I will post when I finally get there. :)

[Archangel]

32-bit version of Windows 2000, Windows XP, Windows Vista, or Windows 7 Operating System (64-bit will not work)

http://www.machsupport.com/


WOW! Gecko sure has grown since I last saw them!
http://www.geckodrive.com/


(Mach and Gecko drives were my first idea for a home CNC system)

Robert
I saw that too, maybe OLD information, cause it works on my wife's Win7 x64, at least it loads and I can manipulate all the controls, no CNC machine attached though. . . .