Little PICs with hi-res A-D ?

Selection table for 8 piners:

Dave.

I agree, that's the best 8 pin PIC I know of. Don't be fooled by the 12F, it's still a 14 bit core like the 16F series.

How about a couple with 'windowing' ? Can that be done to extend the resolution ?

Graham

Eeyore wrote in news: snipped-for-privacy@hotmail.com:

Don't think anything up to 16F has anything better than 10 bits. Use an I2C A/D chip. The drivers are all over the place.

Any particular recommendations ? Cheapish would be nice.

Graham

Eeyore wrote in news: snipped-for-privacy@hotmail.com:

I've used the Microchip MCP3208, 8 channel 12-bit SAR with an SPI interface.

Samples are free, and tend to arrive in 1-2 weeks.

There's a SAR selection page at

They also have dual slopes and sigma-deltas.

LOL @ 2.7V. They really don't want to make life easy for you these days do they ? Oh well, it'll interface to a 10F220 at least ! Just hope everything else likes 2.7V !

Yes.

Thanks for the tip.

Graham

I guess you could try oversampling. If you really need more than 10 bits, maybe an external chip? You really haven't provided much information on your ADC performance requirements.

I think you mis-read - it works from 2.7 to 5.5v

Doesn't need to be fast for one if that's what you mean. It's for scanning some level controls on a pro-audio product. That's why we want better than 10 bit resolution. You might be wondering why but have you ever heard of a phenomenon called 'zipper noise' ?

I also looked the LPC700 and 900 series. They can do 12 bit which may be OK. There are some other factors involved too so a little chewing over is going to be required plus buying an EVM from TI (thankfully sensibly priced) which will be the gain control element (basically a smart MDAC with stunning performance).

Graham

Not remotely what you are asking for, but the MSP430 16-pin parts can be as tiny as an 8-pin DIP and you can get them with 16-bit delta-sigma ADC.

Could also consider the PIC24HJ12GP201 in an SOIC-18 with 12-bit SAR ADC.

Aha ! Yes I was wondering whether there might be something more interesting along those lines. I was wondering AVR too.

What do you program MSP430s in ? Noting that I'm no fan of assembler although the other guy probably would be OK with that.

I'd go LPC 700/900 myself instead for 12 bit.

Graham

Look at some of the Linear SMB/I2C ADC's, they are a bit pricy but better than what you can do in a small PIC.

Cheers

Eeyore wrote in news: snipped-for-privacy@hotmail.com:

Can't integrate the step response on the output? Something similar was done on the control signals of Yamaha gear. Worked fine except they overdid it and made it sluggish. Unless you also notice discrete steps when not actually stepping the resolution might be fine, just needing smoothing of changes.

It's not driving a VCA.

Yes quite ! That's no good here, needs to be 'real time'.

This needs to be used for actual mixing so the steps need to be tiny.

There's several possible solutions including full DSP but that's more work.

Graham

Eeyore wrote in news: snipped-for-privacy@hotmail.com:

Ok, but zipper noise is an output thing, so no go on analog? (Doesn't sound like DSP is needed, and I don't think it can fix this). What's it driving? I might not know an answer but I can give it some thought even if just to understand for myself. As I see it, the smaller the steps, the easier it is to filter adequately without it being sluggish. The idea of zipper noise affecting an input is passing strange, but if it happens, then dither.

I see that making extra work is best avoided by lots of small steps, but if this zipper noise is an audible thing to fix then it must be possible to do it with analog parts. Got to be some timing of a simple filter that ought to help, whatever it's driving. If it can suppres the audible click of a DC change of 1/256th of the dynamic range jumped in one snap, it should work, and be fast enough for real time. How fast CAN a mix engineer move a knob? :)

Eeyore wrote in news: snipped-for-privacy@hotmail.com:

Don't use pots for input-- use encoders. Then the resolution of each step is whatever you program it to be. You can even program speed sensitivity, or course and fine adjust.

Can you hear the difference between steps at 8 bits? Or see it on a scope that isn't looking at a test tone? How about 10 bits?

Is the problem the static step size or the jumps between steps? I assume the latter from the name. If so, I'd expect you can do something to invent fake sub-steps on the input side at reasonable times and the output side would do whatever it would do if you had an input with more real bits.

Mastering equipment.

Very fast.

I have just suggested an analogue solution in fact. It seems like one guy got over excited about some clever looking MDACs that on detailed reading of the data sheet aren't so clever after all.

Graham