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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?

#111

Post by bobmcnamara »

ryukoposting wrote: post #91
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…

Glad I wasn't the only one thinking this. The paragraph ending with "Compare that with a microcontroller ADC with a fixed 3.3 V range: 9 ENOB steps are ~6 mV" also seems to insinuate that no MCU has an analog reference that's independent from the supply, which just isn't true at all. Hell, NXP has a few that have a built-in programmable reference.

> NXP has a few that have a built-in programmable reference

Those also depend on the noise of the supply, see PSRR graph if available.

Re: How bad can a $2.97 ADC be?

#112

Post by bobmcnamara »

beachy wrote: post #64
grishka wrote: post #47

Earlier quoted context omitted.

> 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…

That is very interesting, especially using SMI to talk to rpi. Never seen SMI used in anger before.

I've seen it used as a multi channel logic wave generator. Basically a 16bit wide relatively fast DMA.

Re: How bad can a $2.97 ADC be?

#113

Post by bobmcnamara »

theamk wrote: post #60
grishka wrote: post #47

Earlier quoted context omitted.

> 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.

I've used it on pi1-4. Not sure if Pi5 has SMI on its southbridge

Re: How bad can a $2.97 ADC be?

#115

Post by kragen »

alwa wrote: post #110
kragen wrote: post #105

Earlier quoted context omitted.

I've heard that boiling epoxy in molten colophony for a few hours, like a long-cooked version of rosin potatoes, will also dissolve it. I haven't tried it myself. Colophony is much more expensive than sulfuric or nitric acid, but safer to handle (when not molten) and often easier to get.

I did not know that. Pine rosin is such lovely and versatile stuff. And sure enough: https://m.youtube.com/watch?v=pIpxawdUb4I&t=30m18s …plus it smells much better; and, as you mention, it’s useful for potatoes too! https://bittersoutherner.com/feature/2022/the-elusive-roots-...

These slides from the talk say it only takes 5–20 minutes. I'm not sure it will smell better when you heat epoxy to the specified 320–360°. I'm interested in hearing whether anyone else has tried this.

Re: How bad can a $2.97 ADC be?

#116

Post by shadowpho »

willis936 wrote: post #40
brcmthrowaway wrote: post #8

Has there been any updates on ADC technology? What does SKA/CERN use?

Well, if you're trying to measure DC extremely accurately the old stuff is still golden. Multi-slope is the gold standard and no one will sell you one. Delta-sigma get most of the way there. https://youtu.be/upTgM_S5rAQ And if you want to see CERN's multimeter, check this out. https://youtu.be/D28uSzCs7-k Marco Reps is a treasure.

>Multi-slope is the gold standard and no one will sell you one.

Why not?

Re: How bad can a $2.97 ADC be?

#117

Post by doubleg72 »

jacquesm wrote: post #77
supportengineer wrote: post #75

Earlier quoted context omitted.

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.

Surface grinders generally don’t use CNC, they are a simple machine.

Re: How bad can a $2.97 ADC be?

#118

Post by 5d41402abc4b »

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...

Whats wrong with its external flash and memory?

Re: How bad can a $2.97 ADC be?

#119

Post by userbinator »

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…

Apparently you haven't seen what the datasheets of 7805 regulators look like; or to use a far more complex example, LCD controllers. I do find it amusing that AnalogySemi's datasheet uses basically the same fonts as Linear Technology's, but copy-paste is the norm in the industry, and many companies will require that parts in their design always have a second-source manufacturer, if not more.

Re: How bad can a $2.97 ADC be?

#120

Post by duskwuff »

userbinator wrote: post #119
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…

Apparently you haven't seen what the datasheets of 7805 regulators look like; or to use a far more complex example, LCD controllers. I do find it amusing that AnalogySemi's datasheet uses basically the same fonts as Linear Technology's, but copy-paste is the norm in the industry, and many companies will require that parts in their design always have a second-source manufacturer, if not more.

I've seen some datasheets which were copy/pasted to the extent that some of the example schematics still used the name of the original part.
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