Hello Mitja,

> Take a look at dsPIC30F series. Some of them have 12bit ADC and low pin
> count and they are under $5. I admit that they are not as nice to work
> with as Ti's 24xx series (my personal opinion), but on the other side
> development tools are significantly cheaper (XDS510 vs. ICD2).
> 

Thanks. I did look at these and their pricing would still be ok. 
However, I really need about 14 bits and their 100k converters don't 
look like I could play the usual tricks much to get there.

The only chips around $5 that have a decent ADC built in seem to be the 
MSP430F4xx series. It isn't a DSP but at least it includes a 16bit 
hardware multiplier. I don't know yet whether it will choke with all the 
filters I'd have to cram into it. One serious downside with such 
controllers is their small RAM. Hanging an external RAM onto a uC 
usually eats up most of the port resources.

Regards, Joerg

http://www.analogconsultants.com

Take a look at dsPIC30F series. Some of them have 12bit ADC and low pin
count and they are under $5. I admit that they are not as nice to work
with as Ti's 24xx series (my personal opinion), but on the other side
development tools are significantly cheaper (XDS510 vs. ICD2).

Regrards

Mitja

Hello Tim,

> The '2401 is like the '2812 in that it's really designed for advanced 
> motor control -- that's why the data sheet says "Several advanced 
> peripherals, optimized for digital motor and motion control 
> applications, have been integrated to provide a true single-chip DSP 
> controller."
> 

Yes, and they have some nice PWM capabilities.


> For this sort of thing those high-speed ADC's come in mighty handy, and 
> the precision isn't such a big deal.
> 
> ADI used to make DSPs with built-in stereo codecs that had 16 bits in 
> and out; I don't know what happened to them, or if TI makes anything 
> similar.
> 

I guess the audio market wasn't large enough anymore and modems are all 
ASIC now. They list the ADSP-21990 series, with a fast 14bit converter 
in there. However, the AD web site mentions no price (might not be a 
good sign) and Arrow quotes around $50 for the 4k RAM version. Way too 
much for most of my applications.

There may be some parts from overseas manufacturers but with their often 
rather clumsy web sites that will be hard to find. Also, my recent 
experience with support from EU companies makes me stay away.

So it looks like I'll have so see how many effective bits the 10bit ADCs 
can yield at low frequencies when fully tricked out. The challenge will 
be that the tricks can't contain too many discretes. An external ADC is 
another option but not a nice one.

Regards, Joerg

http://www.analogconsultants.com

Joerg wrote:

> Hello Mitja,
> 
>>> Be careful with that -- the crusty old analog engineer at the place
>>> where we used '2812s described its ADC as "10 bits going on 8" -- I
>>> suspect the '24x is no better.
>>
>>
>> I have some experience with 24xx series ADC, and I must say that it
>> works as specified. The 10bit accuracy can be easily achieved on a dual
>> layer board, even with switching devices nearby on the same board
>> (switching 50 Amps at 40kHz). It is completely different ADC than the
>> one in 28xx series.
>>
> 
> With devices like these that are really more geared towards the audio 
> market I am wondering why they included such a high speed 10bit ADC. A 
> slower 14-16bit would be more practical in many applications. But you 
> can't have it all, I guess.
 >
-snip-

The '2401 is like the '2812 in that it's really designed for advanced 
motor control -- that's why the data sheet says "Several advanced 
peripherals, optimized for digital motor and motion control 
applications, have been integrated to provide a true single-chip DSP 
controller."

For this sort of thing those high-speed ADC's come in mighty handy, and 
the precision isn't such a big deal.

ADI used to make DSPs with built-in stereo codecs that had 16 bits in 
and out; I don't know what happened to them, or if TI makes anything 
similar.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Hello Mitja,

>>Be careful with that -- the crusty old analog engineer at the place
>>where we used '2812s described its ADC as "10 bits going on 8" -- I
>>suspect the '24x is no better.
> 
> I have some experience with 24xx series ADC, and I must say that it
> works as specified. The 10bit accuracy can be easily achieved on a dual
> layer board, even with switching devices nearby on the same board
> (switching 50 Amps at 40kHz). It is completely different ADC than the
> one in 28xx series.
> 

With devices like these that are really more geared towards the audio 
market I am wondering why they included such a high speed 10bit ADC. A 
slower 14-16bit would be more practical in many applications. But you 
can't have it all, I guess.

I am not so worried about dual layer, it's just a matter on spending 
more time with the layouter.

> Regarding the choice of 2401, I prefer 2403 as it has practicaly the
> same footprint but has also SPI port and dedicated JTAG pins
> 

The downside is that the 2403 is also a whole lot more expensive, more 
than twice the cost of a 2401. This rules it out in many designs where 
you want to replace analog circuitry. That is what I plan to do (and 
that's while being an analog EE...). Thing is, even a circuit with more 
than 100 parts costs less than $3 in mass production including the 
circuit board. No chance for any DSP above $4-5.

Regards, Joerg

http://www.analogconsultants.com

Tim Wescott wrote:
> Be careful with that -- the crusty old analog engineer at the place
> where we used '2812s described its ADC as "10 bits going on 8" -- I
> suspect the '24x is no better.

I have some experience with 24xx series ADC, and I must say that it
works as specified. The 10bit accuracy can be easily achieved on a dual
layer board, even with switching devices nearby on the same board
(switching 50 Amps at 40kHz). It is completely different ADC than the
one in 28xx series.

Regarding the choice of 2401, I prefer 2403 as it has practicaly the
same footprint but has also SPI port and dedicated JTAG pins

Mitja

Hello Tim,

>> The TMS also contains a 10bit ADC while the Blackfin doesn't. A 10bit 
>> is not much to write home about but with some offset-stagger tricks it 
>> should be possible to achieve 12-13 bits at low speed. Especially 
>> since its ADC has to be run at a minimum clock frequency of 2MHz anyway.
>>
> Be careful with that -- the crusty old analog engineer at the place 
> where we used '2812s described its ADC as "10 bits going on 8" -- I 
> suspect the '24x is no better.
> 

Yes, ENOB really drops when you approach the max conversion rate. But in 
many of my cases I'd be under 10kHz while the converter can do several 
hundred with ease. That leaves a lot of potential for staggering and 
averaging.

What's pretty sad is how skimpy today's docs are WRT to the analog 
interfaces, including the TMS320 data sheets. Barely one page to 
describe the ADC. Recent app notes like spraa995 also are a bit on the 
fluffy side. Flow charts and marketing speak, not that much meat.


>> You are right, ideally it should be four layers. But I often had to do 
>> two layers even with RF stuff. That was always a white knuckle ride 
>> and you had to sit next to the layouter until the last air wire was 
>> taken car of. My favorite ones know how to handle this but one of them 
>> went through half a carton of cigarettes ;-)
>>
>  From the job, or from you hanging over his shoulder? :)
> 

We were a pretty good team but he kind of hinted that he'd appreciate if 
I'd not throw another one of these his way.

Regards, Joerg

http://www.analogconsultants.com

Joerg wrote:

> Hello Al,
> 
>>
>> The Blackfin is cheaper than the 2105 was when you consider "real" 
>> dollars. It sold for $9.95 for quantity 1+.
>>
> 
> Inflation-adjusted, yes. The problem is that even in med electronics 
> there is a tremendous cost pressure. A piece of equipment comparable to 
> a similar 1990 model might have to sell for 20-30% less today in 
> absolute Dollar numbers. Health care costs still rise because they use 
> so much more equipment.
> 
> 
>> The 218x will probably be available for a long time. You can still buy 
>> 2105s and they were popular maybe 15 years ago. I would probably make 
>> the core supply flexible to accommodate the 2186M as well.
>>
>> That said, the Blackfin may still be cheaper when you consider the 
>> stuff around it and clearly ADI is going to support Blackfin for a 
>> long time.
>>
> 
> Agree, I have quite some faith in AD when it comes to support. They 
> usually told us well before the last order bell when something would be 
> pulled. And most of the time they had an alternate part at the ready 
> that was almost a drop-in replacement.
> 
>>
>> You don't need a parallel boot rom with the Blackfin. you can use an 8 
>> pin serial flash. This reduces pcb space and cost.
>>
> 
>  From that point of view the TMS320LF2401 appears more and more 
> favorable. It has on-board flash and doesn't need to be booted from a 
> serial flash. That also makes it easier to protect the IP. You can lock 
> it from clandestine code readout while the contents of a serial flash 
> can usually be eavesdropped on with a logic analyzer during init.
> 
> The TMS also contains a 10bit ADC while the Blackfin doesn't. A 10bit is 
> not much to write home about but with some offset-stagger tricks it 
> should be possible to achieve 12-13 bits at low speed. Especially since 
> its ADC has to be run at a minimum clock frequency of 2MHz anyway.
> 
Be careful with that -- the crusty old analog engineer at the place 
where we used '2812s described its ADC as "10 bits going on 8" -- I 
suspect the '24x is no better.

> The clear downsides of the TMS are its paltry RAM space and the high 
> power consumption. But at under $4 it still looks like a good deal.
> 
> 
>> I have a two layer 2186M design (with a lot of poured copper) but I 
>> would never consider two layers for any of the newer DSPs. You really 
>> want a ground plane and power planes. The good news is that pcbs don't 
>> cost a lot in 4 layers and the size might be small.
>>
> 
> You are right, ideally it should be four layers. But I often had to do 
> two layers even with RF stuff. That was always a white knuckle ride and 
> you had to sit next to the layouter until the last air wire was taken 
> car of. My favorite ones know how to handle this but one of them went 
> through half a carton of cigarettes ;-)
> 
 From the job, or from you hanging over his shoulder? :)

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Hello Al,

> 
> The Blackfin is cheaper than the 2105 was when you consider "real" 
> dollars. It sold for $9.95 for quantity 1+.
> 

Inflation-adjusted, yes. The problem is that even in med electronics 
there is a tremendous cost pressure. A piece of equipment comparable to 
a similar 1990 model might have to sell for 20-30% less today in 
absolute Dollar numbers. Health care costs still rise because they use 
so much more equipment.


> The 218x will probably be available for a long time. You can still buy 
> 2105s and they were popular maybe 15 years ago. I would probably make the 
> core supply flexible to accommodate the 2186M as well.
> 
> That said, the Blackfin may still be cheaper when you consider the stuff 
> around it and clearly ADI is going to support Blackfin for a long time.
> 

Agree, I have quite some faith in AD when it comes to support. They 
usually told us well before the last order bell when something would be 
pulled. And most of the time they had an alternate part at the ready 
that was almost a drop-in replacement.

> 
> You don't need a parallel boot rom with the Blackfin. you can use an 8 
> pin serial flash. This reduces pcb space and cost.
> 

 From that point of view the TMS320LF2401 appears more and more 
favorable. It has on-board flash and doesn't need to be booted from a 
serial flash. That also makes it easier to protect the IP. You can lock 
it from clandestine code readout while the contents of a serial flash 
can usually be eavesdropped on with a logic analyzer during init.

The TMS also contains a 10bit ADC while the Blackfin doesn't. A 10bit is 
not much to write home about but with some offset-stagger tricks it 
should be possible to achieve 12-13 bits at low speed. Especially since 
its ADC has to be run at a minimum clock frequency of 2MHz anyway.

The clear downsides of the TMS are its paltry RAM space and the high 
power consumption. But at under $4 it still looks like a good deal.


> I have a two layer 2186M design (with a lot of poured copper) but I would 
> never consider two layers for any of the newer DSPs. You really want a 
> ground plane and power planes. The good news is that pcbs don't cost a 
> lot in 4 layers and the size might be small.
> 

You are right, ideally it should be four layers. But I often had to do 
two layers even with RF stuff. That was always a white knuckle ride and 
you had to sit next to the layouter until the last air wire was taken 
car of. My favorite ones know how to handle this but one of them went 
through half a carton of cigarettes ;-)

Regards, Joerg

http://www.analogconsultants.com

Joerg <notthisjoergsch@removethispacbell.net> wrote in
news:TK88f.6461$BZ5.5987@newssvr13.news.prodigy.com: 

> Hello Tim,
> 
>>> Blackfin's are powerful and fairly cheap. They are also low power.
>>> The Blackfin sells for less than a 2105 today.
> 
> 
> Well, they are above $5 and IIRC the 2105 was less. Then again that
> was in 1990's Dollars. The nice thing about the Blackfin is that it
> has a decent amount of RAM while the low end TMS would need additional
> RAM hung onto it, which adds cost to their initially appealing price
> tag. I wouldn't know how to push a decent FFT plus IIR through a
> TMS320LF2401 without extra RAM.

The Blackfin is cheaper than the 2105 was when you consider "real" 
dollars. It sold for $9.95 for quantity 1+.


> 
> 
>>> I think there is a very low cost ADSP-2184N. It would be like a
>>> better 2105.
>>> You can even use the old free tools.
> 
> 
> Those are nice. Thing is, will they continue to live for another 10-15
> years when a design goes into production?

The 218x will probably be available for a long time. You can still buy 
2105s and they were popular maybe 15 years ago. I would probably make the 
core supply flexible to accommodate the 2186M as well.

That said, the Blackfin may still be cheaper when you consider the stuff 
around it and clearly ADI is going to support Blackfin for a long time.
> 
> 
>> That Blackfin actually doesn't look too bad, with significantly lower
>> power dissipation than the 2184 -- but you have to think "only 179
>> pins, why that's much lower than 348!"
>> 
> 
> Especially if it has to fit into a low cost product where too many 
> layers of PCB aren't in the cards. Sometime you even have to make do 
> with two layers.

You don't need a parallel boot rom with the Blackfin. you can use an 8 
pin serial flash. This reduces pcb space and cost.

I have a two layer 2186M design (with a lot of poured copper) but I would 
never consider two layers for any of the newer DSPs. You really want a 
ground plane and power planes. The good news is that pcbs don't cost a 
lot in 4 layers and the size might be small.





> 
> Regards, Joerg
> 
> http://www.analogconsultants.com
> 



-- 
Al Clark
Danville Signal Processing, Inc.
--------------------------------------------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com