pic24 v pic32 ?

[richardb]

Is there any reason someone would use a pic24 instead of a pic32?

[David John Barker]

That's a really good question and I'm sure people will have different views on this. Generated code tends to be smaller with PIC24 when compared to PIC32. The PIC32 architecture is based on MIPS, so some people may find assembler a little different from what they are used to with Microchip. However, some very simple performance tests I have done here show the PICMX150F128B to be a very capable device and I think many people are skipping over PIC24 and jumping straight to PIC32. The PICMX150F128B is also much cheaper than the PIC24HJ128GP502. When the Firewing R2 board is released, I think it will be supplied with a PIC32 by default (with the PIC24 an optional purchase) - not sure on that yet.

Do you have any views on this?

[richardb]

To be honest I hadn't looked at the data sheet for the pic24, and I was wondering if it maybe had 5v tolerant I/o which I can see would be nice for some things/people.

For me the only reason I wanted to try firewing was for more performance.

I always run devices at max speed because in the past its always gone into large equipment and therefore there was no need to save a few mW.

Speed alone can save development time. if I write in a natural way on a fast cpu the code is more obvious in what its doing, and may not involve a re write if its not fast enough.

This was recently an issue for my when I wanted to use a normal PID algorithm. but it just wasn't fast enough so I had to re write it with a compromised feedback error correction algorithm which wasn't as accurate but was good enough.

Richard

[David John Barker]

> 5v tolerant I/o

Both the PIC24 and PIC32 used by Firewing have pins that support up to 5v. I have marked these pins on the R2 board,

http://www.firewing.info/downloads/pdf/pic-pin-map-r2.pdf

Note this is the R2 board! Not R1...

Generally though, anyone moving into the world of PIC24 or PIC32 needs to accept that these chips run at 3.3v. However, having a number of 5v tolerant pins is very useful indeed.

> I wanted to use a normal PID algorithm. but it just wasn't fast enough

You will definitely get a performance kick with this type of thing on a PIC32. In addition, Firewing 32 uses -O2 optmisation which helps even more.