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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?

#71

Post by jacquesm »

Terr_ wrote: post #61
jacquesm wrote: post #54

Earlier quoted context omitted.

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.

I expect it's much easier to acquire fine sandpaper, yet my inner child yearns for laser decapping. (Or I suppose more than "decapping", depending on the depth.)

High power lasers are becoming more and more affordable. Laser ablation is definitely an option but you really want to have some proper fume extraction around that.

Re: How bad can a $2.97 ADC be?

#72

Post by dekhn »

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…

(CERN does a ton of cool electronics design, I didn't realize how much modern physics is electrical engineering).

Re: How bad can a $2.97 ADC be?

#73

Post by magicalhippo »

MountDoom wrote: post #15

> These are cheap, relatively fast, and not particularly good. While they sport impressive-sounding 12- and 16-bit readouts, the effective number of bits (ENOB) is usually around 8 or 9. I don't think that's quite accurate for reasonably modern MCUs. You can typically shake 10+ bits out of them, but you need to take a lot of precautions, such as providing very stable external reference voltage and shutting down unnee…

I tested a few STM32F103 dev boards, using a Siglent SDM3055 multimeter and Siglent SPD330X power supply.

The chip has a 12bit SAR ADC. Layout and board design mattered a lot, but even the worst ones had 10 bits worth, and the best one had nearly 12 bits effective.

That was without doing too much on the software side, meaning the other modules weren't running, besides a single serial output. On the bad boards the serial affected it, but on the good board very little.

Re: How bad can a $2.97 ADC be?

#74

Post by bsder »

NoiseBert69 wrote: post #58
chillingeffect wrote: post #31

Earlier quoted context omitted.

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.

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

No competition or no market?

I can't imagine Espressif is selling much volume of these chips.

The fact that they can't even fix their SPI module would tend to indicate that their engineering staff is very thin.

Re: How bad can a $2.97 ADC be?

#75

Post by supportengineer »

jacquesm wrote: post #54
q3k wrote: post #43

Earlier quoted context omitted.

> 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.

I'm off to build an MCP so AI can control the sandpaper

Re: How bad can a $2.97 ADC be?

#76

Post by throwup238 »

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 prefer Japanese sharpening stones or those DMT diamond whetstones. It’s relative easy to 3d print a jig that converts a woodworking honing guide into an IC holder and you get a feel for how many passes to do very quickly before slowing down and checking each pass.

Re: How bad can a $2.97 ADC be?

#77

Post by jacquesm »

supportengineer wrote: post #75
jacquesm wrote: post #54

Earlier quoted context omitted.

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.

I'm off to build an MCP so AI can control the sandpaper

You may as well start off with one of these then:

https://phillipscorp.com/india/phillipsgrinding/phillips-sur...

All you need is a serial port and some G-codes.

Re: How bad can a $2.97 ADC be?

#78

Post by parsimo2010 »

MountDoom wrote: post #15

> These are cheap, relatively fast, and not particularly good. While they sport impressive-sounding 12- and 16-bit readouts, the effective number of bits (ENOB) is usually around 8 or 9. I don't think that's quite accurate for reasonably modern MCUs. You can typically shake 10+ bits out of them, but you need to take a lot of precautions, such as providing very stable external reference voltage and shutting down unnee…

I think you might both be right- the author may be thinking of lower cost MCUs only aiming for tolerable ADC performance, while you might be thinking of all MCUs, even higher cost.

The RP2350 has 9.2 ENOB on a 12 bit ADC. Sure, you might be able to decimate multiple samples to get more bits out of them, but the spec sheet supports the author's claim (https://www.raspberrypi.com/documentation/pico-sdk/hardware....). There are even lower cost MCUs like the CH32V003 that have even worse ADC performance.

On the other hand, some MCUs can definitely do 10+ bits, such as the STM32H7 line which gets 13+ ENOB from a 16 bit ADC. This is impressive, but the H7 MCUs are literally an order of magnitude more expensive than the RP2350, so they might not be something the author tinkers with much. https://www.st.com/resource/en/application_note/dm00628458-g...

Re: How bad can a $2.97 ADC be?

#79

Post by zsellera »

Most companies have region-specific price lists. My Spotify subscription costs about 60% of what the same plan costs in the US (2200 HUF vs. 11 USD). In the electronics industry, everyone has a separate price list for China.

Btw. the western list price is just an indicative at-most number anyway. Even a small-sized project gets discounted prices when you start talking to a sales rep.

Re: How bad can a $2.97 ADC be?

#80

Post by gsmecher »

q3k wrote: post #51
gsmecher wrote: post #37

Earlier quoted context omitted.

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)

There's nothing wrong with an open clone when everybody is acting in good faith. (In fact, "good faith" does not even necessarily mean "according to the letter of the law in $jurisdiction". Sometimes the law is an ass.)

However, there's nothing more toxic to an OEM than a vendor relationship founded on dishonesty. I know I shouldn't trust them, they know it too, and even if it seems advantageous at first I shouldn't be surprised when they turn on me.

Since these parts are being sold as genuine TI parts, I don't care whether the clone is physically faithful or just functionally faithful - I should treat it like it's poisonous.

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