Help choosing a PIC

[Bobw]

I am not new to PIC's but far from an expert..

Requirements:
Operate from 5 volts
6 inputs for switches. ( I know they can be multiplexed onto one pin)
2 inputs for a quadrature encoder.
4 outputs for relays and led.
Outputs for a glcd.
1k of EPROM would be more than enough.

I have used16f1827 pics before but need a few more I/O pins.

Ideas?

Bob

[medelec35]

Hi Bob,
Take a look here:
http://www.matrixmultimedia.com/mmforum ... 01&#p22195
It might help you.

Martin

[Bobw]

Hey Martin,

While I didn't find that thread on my own. I have been to the Microchip site and have been looking at their chip selector guide.
Trying to really plan this one out, not so trial and error like last time.
Only have the PIC and display left to find.

Thanks

Bob

[medelec35]

I would be inclined to go for the 18F series since they can run at faster speeds (48MHz) than 16F series.
That would be better for updating Glcd.
What about something like 18F4455?
If its good enough for the MIAC

Martin

[Bobw]

I was looking at that one.
Lost all my notes in a computer crash, so really starting from scratch.
I thought there were a couple of chips out there now that had built in support for quadrature encoders (QID?)
Just know having extra I/O pins is a good thing.

[Bobw]

OK,
I am down to the 18F4431 that has the QEI support built in.
And the 18F4455 that does not.
The 4455 is faster and has more memory.
If I hook up the quadrature encoder on the interrupt on change I/O pins what would I loose/gain with the QEI support?

[Benj]

Hello Bob,

I'm afraid I have never used the QEI peripheral so I can't really tell you the upside of using this. The downside is you would probably have to access this using C code.

The upside of using a IOC or timer based encoder is that Flowcode v5 supports this directly and it is very reliable as long as you have the timer set fast enough or the IOC setup correctly on the encoder pins.

[Bobw]

Thanks for the info everyone.
I have decided to use the 18F4455
It may be a bit overkill for my needs but have already added 2 more I/O functions to my list.
I also see it has 3 interrupt pins, and on paper is plenty fast.
Best part is that FC5 supports it.
Bob