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How bad can a $2.97 ADC be?

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Re: How bad can a $2.97 ADC be?

#51

Post by q3k »

gsmecher wrote: post #37
throwup238 wrote: post #30

Earlier quoted context omitted.

Ah oops I missed that. Maybe an ADX111A then?

Oh my - good find, and also, eek. Analogy: https://datasheet.lcsc.com/lcsc/2302211830_analogysemi-ADX11... TI: https://www.ti.com/lit/ds/symlink/ads1115.pdf Analogy's datasheet is directly cribbed from TI's (see TI Fig. 7-7 / Analogy Fig. 22½, pg. 18). This already passes my "run away screaming" threshold for trust, but a decapping would help me understand whether they've stolen the physical design (bad) or just clon…

> or just cloned it (bad)

What's wrong with cloning a chip functionality-wise? This is basically how the industry has operated since its infancy, and what gave us jelly bean logic parts and transistors, x86 and the PC revolution, ...

(just talking about the cloning part here, not counterfeit markings or datasheet copyright infringement, or copying mask work)

Re: How bad can a $2.97 ADC be?

#52

Post by LeifCarrotson »

cushychicken wrote: post #49

OP is making comments about poor performance single cycle of a sigma delta ADC. Single cycle readings defeat the point of sigma delta ADC setups. You're taking many high noise samples and averaging them over time to get a better picture of the average voltage.

OP is using the chip with the data rate set to 8 samples per second.

Natively/internally, it runs at 860 samples per second, and you can configure it to provide that data at a lower sample rate at lower noise levels by averaging multiple readings together internally.

Re: How bad can a $2.97 ADC be?

#53

Post by cycomanic »

magicalhippo wrote: post #39
beachy wrote: post #29

I'd like to know more about the world of ADCs. I've used the ADS1115 with success but only at very slow speeds. On the current project we started with an MCP3208 via SPI. It did the job but only has 8 channels and it's slow (100K samples per sec). To get something faster we switched to ADS7953. It has 16 channels and runs 10 times faster. It's somewhat more complex to code, and you can only get the highest sample rat…

> To get something faster we switched to ADS7953. It has 16 channels and runs 10 times faster. I recall reading about a project at CERN to design a 12bit ADC chip that could sample at tens of GHz, maybe 50 or more. I was perplexed at how they could achieve this. Turned out it was the same we programmers do. Parallel processing. They had taken a 12bit SAR unit which ran at like MHz rates, and just cloned it many times…

You can buy ADCs at over 100 GS/s (keysight, teledyne and tektronix make oscilloscopes using them), however typical ENOBs are more around 5 bits for these. For people interested in this stuff, I there is a video of someone taking apart one of the high speed keysight scopes (I think signal path is the YouTube channel?).

Re: How bad can a $2.97 ADC be?

#54

Post by jacquesm »

q3k wrote: post #43
Hasz wrote: post #42

Earlier quoted context omitted.

I have done this a bunch of different times, mostly to resolve sourcing disputes. Dissolving in boiling sulphuric acid/nitric acid will make quick work of most epoxy packaging IMO, I have mostly seen mislabeling, rebinning, and passing off obvious QC rejects. example from many years ago: https://www.youtube.com/watch?v=e6DfBuPwAAA

> Dissolving in boiling sulphuric acid/nitric acid will make quick work of most epoxy packaging That's the better method of course (results wise), but it's not nearly as accessible, hence my recent evangelism of the virtues of 2000 grit sandpaper.

I like it. I've used sandpaper to solve some interesting problems in the past as well with great success. I suspect we are only seeing the beginnings here in a trend of high-tech applications of fine grit paper.

Re: How bad can a $2.97 ADC be?

#55

Post by Arubis »

cheschire wrote: post #12
throwup238 wrote: post #9

Earlier quoted context omitted.

TI makes all their analog stuff in house so that's unlikely. That's far more common for fabless companies that send their parts off to an outside fab.

What does TI do with their out-of-tolerance products? Straight in the garbage?

Binned wafers are viable source material for photovoltaics.

Re: How bad can a $2.97 ADC be?

#56

Post by slices »

RobKohr wrote: post #28

ADC = Analog to digital converter Takes an analog signal from something like light or sound and convert it into a digital signal. Acronyms introduced in an article should be spelled out at least once please.

I thought they were talking about League of Legends players, whoops

Re: How bad can a $2.97 ADC be?

#57

Post by NoiseBert69 »

squarefoot wrote: post #45
the__alchemist wrote: post #32

Earlier quoted context omitted.

H7s for <$1? I get confused whenever people talk about paying $0.69 for an MCU!

I recalled a few years ago there were shockingly inexpensive MCUs at LCSC and similar far east vendors, but they were never heard before names, so I just checked again out of curiosity and here's a $0.05 one by Cypress. https://www.lcsc.com/product-detail/C2954567.html

I played around with the RISC-V from WCH.

They are huge step ahead: the upcoming CH32H417 has pretty much all PHYs integrated (!). For 10/100M Ethernet, USB-C 5GBbps and USB HS 480Mbps. That dramatically reduces the components needed to get that stuff running.

I also build a small robot with the ultra cheap CH32V003. That's a full fledged 48MHz microcontroller with 16kb flash and 2kb SRAM. Fun little thing.

If you are used to the ST HAL you will be able to work with them within 10 minutes. Their API style is similar.

Re: How bad can a $2.97 ADC be?

#58

Post by NoiseBert69 »

chillingeffect wrote: post #31
NoiseBert69 wrote: post #10

I still have a huge trauma coming from the ESP32 ADC. Why don't they integrate good ADCs? We are waiting for ages now. Non-linear as hell - and evil side effects once you use the calibration curves.

If hate the esp32 adc, let me introduce you to its "fpu." Or its external flash and memory...

But no real competition for on-chip Wifi/BLE around.

Only ugly two-chip solutions or hyper exotic stuff with no community.

Re: How bad can a $2.97 ADC be?

#59

Post by LeifCarrotson »

ZeroConcerns wrote: post #27

Well, I guess a whole-three-genuine-US-dollars is actually pretty expensive for an ADC, and that the person-in-charge-of-your-BOM in one of the countries that can actually still manufacture things can get one for way less than that. Does it work? Well, does your design power up during factory testing, and then pass whatever things your rig (hope you made a few!) has in mind? Well, then, yes, in fact it does...

These numbers add up fast when you have dozens or hundreds of components on your board. A $3 part is often one of the most expensive items on a board! If you're trying to get something shipped to consumers for $20 each, with an enclosure, packaging, shipping, retail markup, and profit...that's a huge price disparity.

Also, and perhaps more importantly, the test rig is a lot simpler and a lot cheaper if you can generally trust manufacturer data. Sure, send off a few samples (likely prototypes with parts from Digikey instead of LCSC) to run extended testing in an environmental chamber with thermal imaging, build an endurance test rig that pushes the button once a second for four weeks to simulate once-daily use for years, whatever you want to do...but after that, if TI says it's good from -40 to +125, you're going to trust them on a lot of the edge cases.

Do 100% testing of the things you can test in-circuit if you can - power it up at room temperature and make sure it works once - but that doesn't mean you get the actual rated performance across all published environmental conditions.

Re: How bad can a $2.97 ADC be?

#60

Post by theamk »

grishka wrote: post #47
beachy wrote: post #29

I'd like to know more about the world of ADCs. I've used the ADS1115 with success but only at very slow speeds. On the current project we started with an MCP3208 via SPI. It did the job but only has 8 channels and it's slow (100K samples per sec). To get something faster we switched to ADS7953. It has 16 channels and runs 10 times faster. It's somewhat more complex to code, and you can only get the highest sample rat…

> The ADS7953 is somewhat of a ferrari, whereas the MCP3208 feels like a Toyota, simple to use, unimpressive performance. What about the AD9226? It only has a single channel but can do up to 65 MSa/s at 12 bits. I bought one as a module for around $12 on AliExpress to experiment with software decoding of analog video. I only run it at 20 MSa/s and only use 8 bits because, funnily enough, the limiting factor is the sp…

For the curious: that blogpost does not mention the Pi model explicitly, but one of the links refers to BCM2835. This means Raspberry Pi Model 1.
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