Worlds Smallest/Cheapest Computer !!!

[paulie]

Introducing AVROS! I challenge anyone to come up with a smaller lower cost personal computer. The computer here being defined as able to load, store, and run programs under user control.  The ability to create programs on-board may also be a consideration.  Below are some photos of my Atmel Mega8 based entry.

Having some idle time on my hands during this long weekend I threw together the DIP prototype.  The whole thing took less than 5 minutes.  Because of fine soldering a miniature QFP version took a little longer but not much.  The circuit is very simple: only a chip and bypass capacitor.  An LED can be added for testing and debugging but that's a luxury.  In any case total cost less than a buck.

On request a wiring diagram and hex file are attached. Fuses are H=c2 L=a4. In this particular image program #0 turns on the LED and returns, #5 turns off, #6 dims and loops, and #7 runs the OS again (same as reset). Of course you can load whatever others you like one byte at a time manually using ':' command or with Hyperterminal "send text file".

[paulie]

The operating system, AVROS, only took me about 45 minutes to write.  It talks at 57kbaud to a PC running Hyperterminal or any other serial monitor.  I found it very convenient to plug in a cheap HC06 bluetooth module linked to my Android phone.  Everything fits in my shirt pocket and I can play around writing little programs while killing time.

Commands are as follows:

'0'-'7' = run user programs (can be 8 small or one big depending on size)
':' = input program in intel format (manually or via text file transfer)
'a' = set address for dump
'd' = dump program page in hex, 'q'=quit, any other key displays next

If no commands are entered within 12 seconds after reset the first program in memory is executed automatically.  Right now there are a few programs pre-loaded.  The first one is actually the Arduino blink demo so if I don't do anything at all the LED will start flashing.  There's also currently a simple calculator and a couple for checking range on nRF24l01 wireless transceivers.  Another for testing an ESP8266 wifi module.

If anyone is interested in building one of these let me know and I'll post a schematic and some code.

[Seekonk]

I must be last of the big spenders.  I'll stick with those on a board with a regulator, some LED and a crystal resonator for $2.25 shipped.  My eyes ain't so good.  But it is time we start looking at a micro as just a chip or transistor.  I've just about given up analog.

[miguelvp]

... In any case total cost less than a buck.

BOM with links where to purchase each item at those prices would be nice because I can't source an ATMEGA8-16PC for under $1 let alone adding the headers and decoupling cap.

As for power I guess it's externally powered, right?

[paulie]

No... Internally powered by a microscopic atomic fuel cell inside the QFP package... Of course it's externally powered like every other computer on the planet. One can hook up a rechargeable 6mm lithium button cell though and still qualify as Worlds Smallest Computer. And it will run for days.

BTW I should have phrased it "WAY under a dollar". A snapshot of one of the Aliexpress listings has been added to first post. 50 cents for new parts is not the best we can do though. I've snagged refurbs for half that. At 2 for a penny the 6 pins and the 0805 cap add almost nothing. So it's quite possible to crank these out for less than half buck each.

[paulie]

I'll stick with those on a board with a regulator, some LED and a crystal resonator for $2.25 shipped.

A quad core Pentium with 800w supply, 16 gigabyte ram, and 4 terabyte HD can be quite useful too.

I also have great fondness for Pro Mini but it is far from the smallest or the cheapest (I know we all like to keep these threads on topic LOL). Fact is there are at least 2 dozen smaller MCU boards than Pro Mini and those are just the ones in my collection.  A few get below an inch but nothing in the 1 cm range like this.

Technically those don't qualify for "personal computer" status either since no ability to load, store, and run programs under user control as is. Best we can do there is use Arduino IDE tools to flash (1 out of 3 ain't bad). Of course one can write programs to provide these capabilities but they are not available out of the box.

And at 40 cents each for m8 on Aliexpress we can build 5 of these for the cost of a single Pro Mini.

[rob77]

... In any case total cost less than a buck.

BOM with links where to purchase each item at those prices would be nice because I can't source an ATMEGA8-16PC for under $1 let alone adding the headers and decoupling cap.

As for power I guess it's externally powered, right?

+1

me too.... need those 16Mhz ATmega8 MCUs under $1 currently i'm getting them for 1.30Euro + VAT (would be 0.95Eur + VAT at 100+ quantitites)

[hamdi.tn]

No... Internally powered by a microscopic atomic fuel cell inside the QFP package...

 

[paulie]

me too.... need those 16Mhz ATmega8 MCUs under $1 currently i'm getting them for 1.30Euro + VAT (would be 0.95Eur + VAT at 100+ quantitites)

In case you missed it check post #1 again Rob... I've added a snapshot from Aliexpress for half dollar in qty 10.

[miguelvp]

http://www.cypress.com/?mpn=CY8C4013SXI-400

Qty 1: $0.40
Qty 10: $0.38
Qty 100: $0.35
Qty 1000: $0.29
Direct from manufacturer, so you know what you get.

8KB Flash
2KB SRAM
8 pin SOIC 4.8mm x 3.81mm (if you bend the pins Edit: 4 mm since the pins are 0.190mm thick) x 1.549mm.
Edit: 1.27mm pitch so easy to wire it up.
with 5 GPIOs, two of those are SWD Data and CLK for programming but they can be re-purposed
VDD: 1.8V-5.5V with 3 decoupling caps (1 1uF, 2 0.1uF)

But I'm not going to buy them just to prove a point

[paulie]

Actually I did buy that exact part along with several others that were under a dollar. The ones without digital blocks are probably the cheapest ARM chips available. While not a big lover of Cypress the company I have come to appreciate the PSOC family too so thanks again for pushing me in that direction.

But there is no way I could have whipped out an equivalent operating system for one of those in less than an hour. It would take weeks if not months. ARM is a great technology but IMO close to Worlds Worst Instruction Set. Maybe second only to PIC or 8051.

ps. I do have my eye on STM8 which are even cheaper with beautiful architecture and instructions similar to 6502. Half the pin spacing of Mega8 can be a bitch though.

[Dinsdale]

That's pretty cool. But a PC? I think that's a stretch.
It should have self-contained human I/O at least. I'd grant the power supply as being separate. But you should be able to draw a schematic, and lay-out a PCB on it (I mean, really, what are we doing here?). Maybe what you have there, with LCD and a membrane keyboard. Smallest size would be with the keyboard rolled up or folded for storage/carrying.

[paulie]

Maybe a little stretch. Let's call it poetic license.

But as far as CAD, keep in mind the original IBM PC had no such capability until years later. We were lucky to get Zork up and running. Also note that many of those PCs controlled factory machines without keyboard or monitor. My cell phone makes for a very compact interface but not cheap by any means. A Hitachi type LCD would be inexpensive but requires lots of pins. I'm considering hooking up one of those cheap Nokia or OLED SPI displays and a $1 hex keypad. This would at least allow creation of programs since the current simplified OS does talk hex.

Just icing on the cake though because even today many personal computers are serving embedded duty without need for fancy human interface. Sometimes just a green button and a red button.

[Psi]

You could get an old version of linux running on a STM arm micro with a little effort.

That would be much more powerful and you could run/compile some of the simple linux apps for it.
You would need some external ram and flash though

[Dinsdale]

OK paulie. Laser projection virtual keyboard. Projected display. That's just a couple of piggy-backs on your chip.
I know you can shrink the CAD software: 1 page schematic, 2in x 2in PCB.

[SL4P]

Seems to me that laying out a PCB to accommodate the 6-pin header, would be time just as well spent as layout for the SMD or DIP part - and get all the pins, automated assembly, physical strength etc... ?

[paulie]

Aside from doubling size and cost a PCB would take 5 weeks instead of 5 minutes. Not great for day after Christmas idle time project. If I were going to produce 1k units that might be the only option but so far don't look like a candidate for crowd funding.  If I went with the STM8 idea maybe the only option too but a PCB would wash away the size and cost advantage of using that chip.

I'm pretty happy with this construction method. In fact just for the heck of it I assembled another miniature version and it only took about 5 minutes. I'm getting better at it.

[SL4P]

Acknowledge all that - no criticism for a one-off / quickie project.

It just falls short in the 'worlds lowest cost computer' category, as the 10 mins to fabricate the rig for each use adds cost to the idea as a generic solution, whereas even a small panellized breakout PCB would only add - say $0.20 to the BOM

Nice fine soldering tho' 

[nuno]

Since an AVR counts, let me show you my toy, besides the AVR it does input and output of sound and light, powered by a CR2032 at the back of the piezo:


photo by André Sier.

Has a ATtiny25, but I could still fit a bigger brother

[Stonent]

Not cheapest or smallest but I love this one: http://www.dos4ever.com/8031board/8031board.html

8051/52 series chips, even OTP ones can be "booted" from an external eprom so you can scavenge chips from boards that you can't reprogram and use the MCS basic firmware and have a basic BASIC based computer.

[SL4P]

Not cheapest or smallest but I love this one: http://www.dos4ever.com/8031board/8031board.html
8051/52 series chips, even OTP ones can be "booted" from an external eprom so you can scavenge chips from boards that you can't reprogram and use the MCS basic firmware and have a basic BASIC based computer.

So even if you don't like BASIC, you have a '...basic BASIC based computer.'

[westfw]

You could get an old version of linux running on a STM arm micro

I dunno.  They tend to be pretty ram-poor.  unix really likes RAM.
OTOH, 2.10bsd runs on some of the bigger PIC32 chips (512k flash, 128k RAM), but I haven't heard anything about it running on similarly sized ARM chips.  (I guess that even the relatively small PIC32s implement a bit of virtual addressing.  Interesting.)

[dannyf]

use the MCS basic firmware

That's my first entry into mcu, in the 1980s, where I found my first pile of gold.

[Psi]

It's not the smallest unless you use a 3x3mm DFN chip.

Make something with a MC9RS08   

[westfw]

Hmm.   I'm not really impressed any more by the "$1 computer connects to $500 laptop via $5 USB/Serial computer" hacks.

What do you think the smallest/cheapest "useful" computer would look like?   SW video to your TV and  input from your IR remote?  One of those esp8266 modules running a Lua interpretter OVER the wifi link? (not quite there yet, I guess.)  Something with BLE talking to your cellphone?

I guess the core CPU/etc is no longer the limiting factor.  We would need to agree on which IO devices count as "so common that their cost doesn't count", and focus on talking to them...