Too Much Processor?

Hi all. Currently I'm working on making a digital tachometer. I have most of the code working off of a synthesized "tach signal". I'm designing a comparator input circuit that will translate any tach signal into a 5V square wave equivalent.

I'm doing all of this on a 18F46K22, but I'm thinking that it's way overkill of a processor for this application and may go with something a bit smaller. Clearly this application doesn't need a 40-pin processor...can probably get away with an 18-pin device easily. I'll need at least 7 pins for the LCD display, one of them with PWM available for LCD contrast, and 1 for the tach signal input.

In terms of available on-chip hardware, at what point do you consider a processor to be too much processor for the application?

Pretty well anything in your case, as it's a VERY low-spec requirement

Personally, I've 'recently' moved from the 14 bit 16F628/877 etc. to the enhanced 14 bit series, the 16F1827/1847 etc.

The enhanced parts have a lot of useful enhancements (the multi-frequency internal oscillator is one of them), and are also considerably cheaper.

I've played briefly with the 18F series, but they seem a bit 'over complicated' and of course are more expensive.

Yes I moved from the 16F to the 18F series parts, but have yet to try the enhanced 16F parts. They seem like a "middle ground" between the 16F and 18F. Perhaps I'll have to order a couple and play with them a bit.

If you program mainly in C I would stick to the 18 series. This might be something to look at. **broken link removed**

Jon Wilder said:

Yes I moved from the 16F to the 18F series parts, but have yet to try the enhanced 16F parts. They seem like a "middle ground" between the 16F and 18F. Perhaps I'll have to order a couple and play with them a bit.

Click to expand...

Enchanced 16F have lots of advanced features, such as shadow registers, and are somewhat better than older 18F, especially when considering price.

Jon Wilder said:

one of them with PWM available for LCD contrast,

Click to expand...

Jon, been looking into sw lcd contrast for a project , does the contrast pin not need a steady voltage , how are you doing that please ?

Hello,
Tachometer can be made with 1 min timer capture counting using encoder or some sort IR beam on white/black surface.

granddad said:

Jon, been looking into sw lcd contrast for a project , does the contrast pin not need a steady voltage , how are you doing that please ?

Click to expand...

It's done all the time that way, not that I've ever done it - but sticking a resistor and capacitor on the pin should smooth it out, I don't think it draws much current?.

Have you tried google? (I just did):

**broken link removed**