Little PICs with hi-res A-D ?

E

Eeyore

Guest
Me ? A PIC ? You must think I'm going mad !

No, it's for someone else I may work on a project with and he's into
PICs. He wants a little 8 pin jobbie with an onboard A-D. Currently he's
looking at a 16F220 IIRC. That only has an 8 bit A-D.

I reckon we need 12 bits off the top of my head but 16 would be nice.

Any suggestions ? I'm totally unfamiliar with their range and he's off
on dog-sitting holiday for 2 weeks.

Graham
 
David L. Jones wrote:
On Oct 14, 6:20 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com
wrote:
Me ? A PIC ? You must think I'm going mad !

No, it's for someone else I may work on a project with and he's into
PICs. He wants a little 8 pin jobbie with an onboard A-D. Currently
he's looking at a 16F220 IIRC. That only has an 8 bit A-D.

I reckon we need 12 bits off the top of my head but 16 would be nice.

Any suggestions ? I'm totally unfamiliar with their range and he's
off on dog-sitting holiday for 2 weeks.

Selection table for 8 piners:
http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=1001&mid=10&lang=en&pageId=74

12F683 is the pick of the bunch:
http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010115
only 10bit ADC, Microchip haven't figured out how to do 12 bit yet.
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.
 
On Oct 14, 6:20 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com>
wrote:
Me ? A PIC ? You must think I'm going mad !

No, it's for someone else I may work on a project with and he's into
PICs. He wants a little 8 pin jobbie with an onboard A-D. Currently he's
looking at a 16F220 IIRC. That only has an 8 bit A-D.

I reckon we need 12 bits off the top of my head but 16 would be nice.

Any suggestions ? I'm totally unfamiliar with their range and he's off
on dog-sitting holiday for 2 weeks.
Selection table for 8 piners:
http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=1001&mid=10&lang=en&pageId=74

12F683 is the pick of the bunch:
http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010115
only 10bit ADC, Microchip haven't figured out how to do 12 bit yet.

Dave.
 
Anthony Fremont wrote:

David L. Jones wrote:
Eeyore wrote:
Me ? A PIC ? You must think I'm going mad !

No, it's for someone else I may work on a project with and he's into
PICs. He wants a little 8 pin jobbie with an onboard A-D. Currently
he's looking at a 16F220 IIRC. That only has an 8 bit A-D.

I reckon we need 12 bits off the top of my head but 16 would be nice.

Any suggestions ? I'm totally unfamiliar with their range and he's
off on dog-sitting holiday for 2 weeks.

Selection table for 8 piners:
http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=1001&mid=10&lang=en&pageId=74

12F683 is the pick of the bunch:
http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010115
only 10bit ADC, Microchip haven't figured out how to do 12 bit yet.

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 <rabbitsfriendsandrelations@hotmail.com> wrote in
news:48F45665.A5C64205@hotmail.com:

Me ? A PIC ? You must think I'm going mad !

No, it's for someone else I may work on a project with and he's into
PICs. He wants a little 8 pin jobbie with an onboard A-D. Currently he's
looking at a 16F220 IIRC. That only has an 8 bit A-D.

I reckon we need 12 bits off the top of my head but 16 would be nice.

Any suggestions ? I'm totally unfamiliar with their range and he's off
on dog-sitting holiday for 2 weeks.

Graham

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.
--
Scott
Reverse name to reply
 
Scott Seidman wrote:

Eeyore wrote

Me ? A PIC ? You must think I'm going mad !

No, it's for someone else I may work on a project with and he's into
PICs. He wants a little 8 pin jobbie with an onboard A-D. Currently he's
looking at a 16F220 IIRC. That only has an 8 bit A-D.

I reckon we need 12 bits off the top of my head but 16 would be nice.

Any suggestions ? I'm totally unfamiliar with their range and he's off
on dog-sitting holiday for 2 weeks.

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 <rabbitsfriendsandrelations@hotmail.com> wrote in
news:48F49634.B12A0710@hotmail.com:

Scott Seidman wrote:

Eeyore wrote

Me ? A PIC ? You must think I'm going mad !

No, it's for someone else I may work on a project with and he's
into PICs. He wants a little 8 pin jobbie with an onboard A-D.
Currently he's looking at a 16F220 IIRC. That only has an 8 bit
A-D.

I reckon we need 12 bits off the top of my head but 16 would be
nice.

Any suggestions ? I'm totally unfamiliar with their range and he's
off on dog-sitting holiday for 2 weeks.

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
I've used the Microchip MCP3208, 8 channel 12-bit SAR with an SPI
interface.
http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010534

16-pin DIPs are available. Less than $5 in small quantities. I think
you need 4 bits to interface to it, so plan accordingly. I2C uses one
less bit, if I recall.

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

There's a SAR selection page at
http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=11021&mid=
10&lang=en&pageId=79

They also have dual slopes and sigma-deltas.

--
Scott
Reverse name to reply
 
Scott Seidman wrote:

Eeyore wrote
Scott Seidman wrote:
Eeyore wrote

Me ? A PIC ? You must think I'm going mad !

No, it's for someone else I may work on a project with and he's
into PICs. He wants a little 8 pin jobbie with an onboard A-D.
Currently he's looking at a 16F220 IIRC. That only has an 8 bit
A-D.

I reckon we need 12 bits off the top of my head but 16 would be
nice.

Any suggestions ? I'm totally unfamiliar with their range and he's
off on dog-sitting holiday for 2 weeks.

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.


I've used the Microchip MCP3208, 8 channel 12-bit SAR with an SPI
interface.
http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010534
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 !


16-pin DIPs are available. Less than $5 in small quantities. I think
you need 4 bits to interface to it, so plan accordingly. I2C uses one
less bit, if I recall.
Yes.


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

There's a SAR selection page at
http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=11021&mid=
10&lang=en&pageId=79

They also have dual slopes and sigma-deltas.
Thanks for the tip.

Graham
 
Eeyore wrote:
Anthony Fremont wrote:

David L. Jones wrote:

12F683 is the pick of the bunch:
http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010115
only 10bit ADC, Microchip haven't figured out how to do 12 bit yet.

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 ?
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.
 
On Tue, 14 Oct 2008 14:22:29 +0100, Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:

Scott Seidman wrote:

Eeyore wrote
Scott Seidman wrote:
Eeyore wrote

Me ? A PIC ? You must think I'm going mad !

No, it's for someone else I may work on a project with and he's
into PICs. He wants a little 8 pin jobbie with an onboard A-D.
Currently he's looking at a 16F220 IIRC. That only has an 8 bit
A-D.

I reckon we need 12 bits off the top of my head but 16 would be
nice.

Any suggestions ? I'm totally unfamiliar with their range and he's
off on dog-sitting holiday for 2 weeks.

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.


I've used the Microchip MCP3208, 8 channel 12-bit SAR with an SPI
interface.
http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010534

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 !
I think you mis-read - it works from 2.7 to 5.5v
 
Anthony Fremont wrote:

Eeyore wrote:
Anthony Fremont wrote:
David L. Jones wrote:

12F683 is the pick of the bunch:
http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010115
only 10bit ADC, Microchip haven't figured out how to do 12 bit yet.

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 ?

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.
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
 
On Tue, 14 Oct 2008 09:20:53 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

Me ? A PIC ? You must think I'm going mad !

No, it's for someone else I may work on a project with and he's into
PICs. He wants a little 8 pin jobbie with an onboard A-D. Currently he's
looking at a 16F220 IIRC. That only has an 8 bit A-D.

I reckon we need 12 bits off the top of my head but 16 would be nice.

Any suggestions ? I'm totally unfamiliar with their range and he's off
on dog-sitting holiday for 2 weeks.

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.
 
Spehro Pefhany wrote:

Eeyore wrote:

Me ? A PIC ? You must think I'm going mad !

No, it's for someone else I may work on a project with and he's into
PICs. He wants a little 8 pin jobbie with an onboard A-D. Currently he's
looking at a 16F220 IIRC. That only has an 8 bit A-D.

I reckon we need 12 bits off the top of my head but 16 would be nice.

Any suggestions ? I'm totally unfamiliar with their range and he's off
on dog-sitting holiday for 2 weeks.

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.
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.


Could also consider the PIC24HJ12GP201 in an SOIC-18 with 12-bit SAR
ADC.
I'd go LPC 700/900 myself instead for 12 bit.

Graham
 
"Eeyore" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:48F45665.A5C64205@hotmail.com...
Me ? A PIC ? You must think I'm going mad !

No, it's for someone else I may work on a project with and he's into
PICs. He wants a little 8 pin jobbie with an onboard A-D. Currently
he's
looking at a 16F220 IIRC. That only has an 8 bit A-D.

I reckon we need 12 bits off the top of my head but 16 would be nice.

Any suggestions ? I'm totally unfamiliar with their range and he's off
on dog-sitting holiday for 2 weeks.

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 <rabbitsfriendsandrelations@hotmail.com> wrote in
news:48F51445.1A6AF9F2@hotmail.com:

You might be wondering why but have you ever heard of a
phenomenon called 'zipper noise' ?
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.
 
Lostgallifreyan wrote:

Eeyore wrote

You might be wondering why but have you ever heard of a
phenomenon called 'zipper noise' ?

Can't integrate the step response on the output?
It's not driving a VCA.


Something similar was done on the control signals of Yamaha gear. Worked fine
except they overdid it and made it sluggish.
Yes quite ! That's no good here, needs to be 'real time'.


Unless you also notice discrete steps when not actually
stepping the resolution might be fine, just needing smoothing of changes.
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 <rabbitsfriendsandrelations@hotmail.com> wrote in
news:48F5D6C1.62680430@hotmail.com:

Lostgallifreyan wrote:

Eeyore wrote

You might be wondering why but have you ever heard of a
phenomenon called 'zipper noise' ?

Can't integrate the step response on the output?

It's not driving a VCA.


Something similar was done on the control signals of Yamaha gear.
Worked fine except they overdid it and made it sluggish.

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


Unless you also notice discrete steps when not actually
stepping the resolution might be fine, just needing smoothing of
changes.

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
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 <rabbitsfriendsandrelations@hotmail.com> wrote in
news:48F5D6C1.62680430@hotmail.com:

Lostgallifreyan wrote:

Eeyore wrote

You might be wondering why but have you ever heard of a
phenomenon called 'zipper noise' ?

Can't integrate the step response on the output?

It's not driving a VCA.


Something similar was done on the control signals of Yamaha gear.
Worked fine except they overdid it and made it sluggish.

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


Unless you also notice discrete steps when not actually
stepping the resolution might be fine, just needing smoothing of
changes.

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
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.

--
Scott
Reverse name to reply
 
You might be wondering why but have you ever heard of a
phenomenon called 'zipper noise' ?

Unless you also notice discrete steps when not actually
stepping the resolution might be fine, just needing smoothing of changes.

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

--
These are my opinions, not necessarily my employer's. I hate spam.
 
Lostgallifreyan wrote:

Eeyore wrote
Lostgallifreyan wrote:
Eeyore wrote

You might be wondering why but have you ever heard of a
phenomenon called 'zipper noise' ?

Can't integrate the step response on the output?

It's not driving a VCA.

Something similar was done on the control signals of Yamaha gear.
Worked fine except they overdid it and made it sluggish.

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

Unless you also notice discrete steps when not actually
stepping the resolution might be fine, just needing smoothing of
changes.

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.

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?
Mastering equipment.


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? :)
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
 

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