Everything You Wanted To Know About Padauk MCUs And More

At this point you’d need to have lived underneath a rock somewhere on the dark side of the Moon to not have heard about these amazing, 3-cent microcontrollers. A number of places have pitched in on them, but comprehensive reviews, let alone a full-blown review of the entire ecosystem surrounding these Padauk MCUs have been scarce. Fortunately, [Jay Carlson] has put in a lot of effort to collect everything you could possibly want to know about anything Padauk.

The most important take-away is that these MCUs do not have any kind of communication peripherals. UARTs, I2C, and SPI all have to be done in software. They’re not very great at low-power or battery-powered applications due to high power usage. Essentially you’ll be using GPIO pins a lot. On the other hand, its multi-CPU context, FPPA feature is rather interesting, with the article covering it in detail.

As for the development tools, [Jay] came away very impressed with the In-Circuit Emulation (ICE) instead of running code on an MCU, as this can reduce development times significantly. This makes even the OTP (one-time programmable) property of most Padauk MCUs less significant than one might at first assume.

Then there’s the actual programming of the MCUs. The Micro C compiler Padauk provides essentially implements a sub-set of the C language, with some macros to replace things like for loops. Initially this may seem like a weird limitation, until you realize that these MCUs have 64 to 256 bytes of SRAM. That’s bytes, without any prefixes.

Finally, [Jay] shows off a couple of test projects, including a NeoPixel SPI adapter and bike light, which are all available on Github. The WS2812b project is something we have seen before, for example this project from [Anders Nielsen] (featured in the article image), which provides another take on this range of MCUs.

Did reading [Jay]’s article change your mind on these Padauk parts? Have you used these MCUs and ICE parts before? Feel free to leave your thoughts in the comments.

30 thoughts on “Everything You Wanted To Know About Padauk MCUs And More

          1. Maybe the Tiny10. The 85 has a lot more to offer, at least compared to the 3 cent Padauk… then again, at about $1 each for the 85, it better! But as probably 8 out of 10 projects I’ve used the 85 on haven’t needed all it’s capabilities, the Padauks are definitely interesting chips.

      1. If you design a Padauk into a production product, you might want to start looking for another job ASAP.

        My reel has only one date and revision code on every part, but at least three different dies (I only uncapped ten). Two even had notably different process geometry. Padauk is not a fab.

        Serious products wouldn’t use these parts due to the risk involved. Hobbyist projects are better off with something like the ESP32 if the fun is in getting the project completed. If you get your kicks by trudging through needless hurdles along the way and need to save $0.15 on your hobby project… then this is for you.

    1. STM8S003 from ST are only $0.20 from China. It is a decent low cost alternative. They have 1K SRAM, 8K FLASH and usual peripheral. It uses $2 STLinkV2 hardware debugger. ST license Cosmic C compiler and provide an IDE with source level debugger. There is SDCC if you want.

  1. Never heard of them either.

    Maybe a great tradeoff if you are going to design a product that you intend to sell millions of and expect it to retail for $1.
    Spend lots of hours jumping thru software hoops to make your code work.

    Or, spend $3 on a real micro like PIC, AVR, etc and get the code up an running in 10X less time.

    I know what I would do.

  2. Heh, my first job involved working with PIC16 MCUs and specifically figuring out all sorts of unholy tricks up to and including witchcraft and pacts with unsavory ancient deities to cram more features into those 192 bytes of RAM and 4K code space (what’s worse is you couldn’t even access all 192 bytes as a flat address space, but rather there was a bank select register (aliased to both banks) to contribute bit 7, then in each bank addresses 0-31 were special registers and 32-127 were SRAM).

    Nostalgia aside, I don’t know as I’d reach for one of these (or an 8-bit PIC for that matter) these days unless I had a _really_ good reason to wring the last few cents out of the BOM.

    1. I can also entertain the thought that given the task to start with a CPLD / low density FPGA and to implement requisite peripherals, the most generic solution would end up being what we have at hand: all-hardened functionality with a simple processor core and memories.
      It’s ironic how this is the inverse of how processors started – with basically just the ALU, then slowly growing I/O and basic peripheral blocks.

  3. Some of the features described like “multiple cpu contexts” and “wait” and “delay” instructions exist in other microcontrollers. XMOS packs up to 8 logical cores, per physical core, has very clever wait and delay functionality. The Parallax Propeller (P1) has wait and delay too, you can wait for pin change and delay for a number of clocks using the free running counter.
    Nice to see these features at this price point !

  4. Never had the need to go that low in a feature set of a microcontroller. I’d probably still opt for an 8051 core, like something out of the EFM8BB1 family, just to have the convenience of hardware-peripherals (I2C, SPI, UART, ADC, Timers,…) and stay around the 0.3$ price range.

    1. This would be a great topic for a post!

      I’m sort of passively aware that 8051’s are in everything, and I’ve certainly bought my share of USB devices that were so cheap the micro MUST’ve been no more than a few cents of the BoM, but…

      …I’ve never thought of them as something that I-the-hobbyist could buy and program and do useful things with. Never did get my head around the 8051 toolchain, perhaps because it’s such an old and storied architecture there are numerous toolchains to pick from.

      But tell us about your favorite, eh?

  5. Well done that man – excellent resource.

    Can’t say they’re the chip for me (I’m still trying to find time to play with the SWM050), but they’re definitely worth knowing about.

    1. I get a laugh from people thinking a reputable company would use this thing in production.

      Cool gimmick product though. Maybe if I ever need to make a few hundred of a throw-away hobby project and want to spend more hours than dollars.

  6. I’d like to buy a bunch of them so that I can make useless stuff that I would normally not make because of the cost. It would be a great feeling to be like, “hey this thing’s only 3c, lets make a blinky LED, or hardcoded, tvbgone or something

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