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The “terrible” 3 cent MCU – a short survey of sub $0.10 microcontrollers

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Re: The “terrible” 3 cent MCU – a short survey of sub $0.10 microcontrollers

#51

Post by azinman2 »

tluyben2 wrote: post #11

When getting into a project, I usually work with someone in the hardware design space (I can do larger electronics myself and thus prototypes, but I'm hired for very small circuit projects) and after creating a prototype, we usually start searching for the the cheapest MCU (and other components) that fit the project. Spending a lot of time doing assembly and making it fit the constrained memory will pay off when doin…

Any consideration as to why a chip might be cheaper (e.g. worst labor practices, worse environmental practices, etc)?

Re: The “terrible” 3 cent MCU – a short survey of sub $0.10 microcontrollers

#52

Post by tasty_freeze »

vardump wrote: post #43
petra wrote: post #31

Earlier quoted context omitted.

Here's this experiment sort-of running: WCH, which sells cheap mcu's(like $0.25 8051-mcu with usb/16Kflash) is working on a risc-V bluetooth mcu: https://www.cnx-software.com/2019/02/16/wch-ch572-risc-v-mcu... And since risc-v has versions somewhere around 5K-10K gates, well, a lower end mcu isn't far, probably. Still, it would be interesting to think how we can get from that, to standard peripherals, and standard pi…

> And since risc-v has versions somewhere around 5K-10K gates, well, a lower end mcu isn't far, probably. 5-10k? Seriously? That's amazing. Z80 had 8500. According to Wikipedia, even truly simple and bare bones 6502 had 3510 or 3218.

The Z80 had that many transistors, not gates

The CMOS rule of thumb is one gate is 4 transistors (eg a 2-input NAND). But the first Z80 was nmos, and so the equivalent count is harder to state. 3 transistors per 2 input nmos gate is a rough first order guess, but in nmos wide gates still need only a single load resistor, and designers sometimes used dynamic logic to save even more transistors.

Re: The “terrible” 3 cent MCU – a short survey of sub $0.10 microcontrollers

#53

Post by vardump »

tasty_freeze wrote: post #52
vardump wrote: post #43

Earlier quoted context omitted.

> And since risc-v has versions somewhere around 5K-10K gates, well, a lower end mcu isn't far, probably. 5-10k? Seriously? That's amazing. Z80 had 8500. According to Wikipedia, even truly simple and bare bones 6502 had 3510 or 3218.

The Z80 had that many transistors, not gates The CMOS rule of thumb is one gate is 4 transistors (eg a 2-input NAND). But the first Z80 was nmos, and so the equivalent count is harder to state. 3 transistors per 2 input nmos gate is a rough first order guess, but in nmos wide gates still need only a single load resistor, and designers sometimes used dynamic logic to save even more transistors.

Ohh... This is embarrassing! I work in embedded/low level and I have always thought that gate == transistor. It's really obvious in retrospect...

I stand corrected.

Re: The “terrible” 3 cent MCU – a short survey of sub $0.10 microcontrollers

#54

Post by childintime »

vardump wrote: post #38
benj111 wrote: post #20

Earlier quoted context omitted.

"metric butt-load of mask-programmable ROM" What would that be in this context? I'm guessing we're talking KB rather than TB?

I'd guess about 1 MB order of magnitude. That would be a butt-load even for samples. 1 MB would be enough for 45 seconds audio at 8 bit PCM @22 kHz. If they're half competent, they could use ADPCM or much better (and cheaper to decode too!) vector quantization. With VQ, you could go even down to ~1 bits (~6 minutes of audio per megabyte) per sample while maintaining good audio quality. Decoding is very simple, so 650…

> [Vector quantization] Decoding is very simple.

Do you have an encoder/decoder to point us to?

Re: The “terrible” 3 cent MCU – a short survey of sub $0.10 microcontrollers

#55

Post by sitkack »

pkaye wrote: post #25
ska wrote: post #13

Earlier quoted context omitted.

It's pretty easy to make the hassle worthwhile, if you are selling (particularly many) millions of things. Even saving a dime on BOM for a million units shipped will pay an engineer year, roughly. I still remember a friend relating with a mixture of horror and fondness that in 15 years probably the biggest impact he ever had to the bottom line of [big computer manufacturer no longer in existence] was re-routing a PCB…

A product I was working on had different variants based on what parts are populated. There were config resistors to help route the signals based on what was populated. I replaced that all with a simple software lookup table in firmware to reroute the signals correctly. Furthermore I figured out how to auto-detect the dozens of supported configurations on first bootup. The PCBs were very small so I made the board desi…

I would hire you. These techniques should be applied pervasively.

Could you write a guide? I would buy it.

Re: The “terrible” 3 cent MCU – a short survey of sub $0.10 microcontrollers

#56

Post by vardump »

childintime wrote: post #54
vardump wrote: post #38

Earlier quoted context omitted.

I'd guess about 1 MB order of magnitude. That would be a butt-load even for samples. 1 MB would be enough for 45 seconds audio at 8 bit PCM @22 kHz. If they're half competent, they could use ADPCM or much better (and cheaper to decode too!) vector quantization. With VQ, you could go even down to ~1 bits (~6 minutes of audio per megabyte) per sample while maintaining good audio quality. Decoding is very simple, so 650…

> [Vector quantization] Decoding is very simple. Do you have an encoder/decoder to point us to?

VQ is a very well known technique. For something quick, you might be interested to check this blog post about (unmodified) C64 playing high quality audio at 44.1/48 kHz, VQ compressed down to 96-128 kbit/s: https://brokenbytes.blogspot.com/2018/03/a-48khz-digital-mus...

There's some decoder code there as well.

Re: The “terrible” 3 cent MCU – a short survey of sub $0.10 microcontrollers

#57

Post by thaeli »

throwaway2048 wrote: post #33
firethief wrote: post #32

> They address a specific category of low-cost, high volume, non-serviceable products with limited functionality. You need to wait for the push of a button and then let an LED flash exactly five times? You need to control a battery-operated night light? The sub $0.10 MCU is your friend to reduce BOM and shorten development time. If you're allergic to 555s, I guess?

These are cheaper than 555s, more easily available in various footprints, need almost no supporting passive circuity or glue logic, lower power usage, and more flexible to boot. Popularity of the 555 waned a long, long time ago.

More accurate timers, too. It's bizarre to think that "program a microcontroller" is actually cheaper - even in small quantity - than the 555 designs I remember building as a kid.

(In single quantities from LCSC the cheapest 555 is $0.07 and the cheapest Paduak microcontroller is $0.04 - in quantity the 555 is $0.04 and the Paduak is $0.025. Plus fewer support passives with the Paduak.)

Re: The “terrible” 3 cent MCU – a short survey of sub $0.10 microcontrollers

#58

Post by nickpsecurity »

jerryr wrote: post #28
dbcurtis wrote: post #3

These have their uses. A friend who frequently does contract development in the toy space has (or at least used to have) a favorite go-to MCU that costs under $0.06 in bare die. It is essentially a 6502 with 100 bytes of RAM and a metric butt-load of mask-programmable ROM. It was originally designed for greeting cards. He has designed it into toys. It is hard to use, you need a dev kit and a good relationship with th…

That sounds very similar to my experience with toy development. For a toy that played a bunch of pre-recorded sounds, we used a 4-bit Winbond MCU (their MCU division is now Nuvoton) that had a tiny bit of RAM and a ton of mask ROM. Firmware development was done in assembly and targeted a huge (physically large) emulator for test/debug. When we were satisfied with the firmware, we'd send it off to our CM, who would th…

Well, I'm curious which project used a 4-bitter. Jack Gansle and Robert Cravatta did a survey a while back:

http://www.embeddedinsights.com/channels/2010/12/10/consider...

http://www.ganssle.com/rants/is4bitsdead.htm

The two examples were timepiece designs and Gilette Fusion ProGlide. On top of getting yours, I'm curious if any of these cheap MCU's in the article could today have met whatever your requirements were for a 4-bitter?

Re: The “terrible” 3 cent MCU – a short survey of sub $0.10 microcontrollers

#59

Post by coupdejarnac »

azinman2 wrote: post #51
tluyben2 wrote: post #11

When getting into a project, I usually work with someone in the hardware design space (I can do larger electronics myself and thus prototypes, but I'm hired for very small circuit projects) and after creating a prototype, we usually start searching for the the cheapest MCU (and other components) that fit the project. Spending a lot of time doing assembly and making it fit the constrained memory will pay off when doin…

Any consideration as to why a chip might be cheaper (e.g. worst labor practices, worse environmental practices, etc)?

I'm going to hazard a guess that a lot of these cheapo microcontrollers have cores, uh, not developed in-house.

Re: The “terrible” 3 cent MCU – a short survey of sub $0.10 microcontrollers

#60

Post by jerryr »

nickpsecurity wrote: post #58
jerryr wrote: post #28

Earlier quoted context omitted.

That sounds very similar to my experience with toy development. For a toy that played a bunch of pre-recorded sounds, we used a 4-bit Winbond MCU (their MCU division is now Nuvoton) that had a tiny bit of RAM and a ton of mask ROM. Firmware development was done in assembly and targeted a huge (physically large) emulator for test/debug. When we were satisfied with the firmware, we'd send it off to our CM, who would th…

Well, I'm curious which project used a 4-bitter. Jack Gansle and Robert Cravatta did a survey a while back: http://www.embeddedinsights.com/channels/2010/12/10/consider... http://www.ganssle.com/rants/is4bitsdead.htm The two examples were timepiece designs and Gilette Fusion ProGlide. On top of getting yours, I'm curious if any of these cheap MCU's in the article could today have met whatever your requirements were f…

It was also for a low-cost audio application, but it wasn't a toy. This was back in 2001 or so. The MCUs in this article all only have ~1KB ROM, which wouldn't have been enough for our audio samples. We needed >256KB. The "4-bitness" was just incidentally what Winbond offered with a large ROM at the time. However, the SunPlus that we later used in the toy also offered a large ROM with an 8-bit CPU for a similar cost. So, while I can't authoritatively say that 4-bit is dead, it does seem like there are a lot of alternatives in similar price ranges now.
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