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Comments (103)

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  nine_k
  > So, which pins could be combined with SDIO's three? After much thinking, the solution is obvious. RAM's nCS can be the SD card's CLK. RAM's CLK can be the SD card's CMD. RAM's MOSI can be the SD card's DAT. Try and figure out all the possible interactions with each device and what that would look like to the other, to convince yourself that it will work safely.This is truly a brilliant hack, well worth publishing at Hacker News.
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  em3rgent0rdr
  I'm always a bit saddened to see that a separate chip is the go-to method to interface with USB. Unfortunately USB is an incredibly-complex protocol that it seems anything beyond a basic V-USB running USB 1.1 at low-speed is generally not doable without specialized hardware and a significant software stack. Meanwhile a protocol like SPI is ridiculously simple...the minimum hardware needed is a shift register that can be clocked fast enough. I miss how desktop and labtops used to have an exposed serial and parallel port, which could communicate at this low level. I often wonder if instead of USB existing that we instead stuck with UART, I2C, or SPI multidrop (using a small set of standard clock rates) for simple peripherals (maybe over a single connector like the 4-pin JST SH cable for Stemma QT, Qwiic and Grove) over a short distance, and then jumped to IEEE 802.3 Ethernet links for data-heavy peripherals like monitors and external drives. Then instead of having to have separate support for USB and Ethernet, you just would support Ethernet links.
• blacklion
  It is very cool project, buy I think author (I know, you will read this) take it to the extreme. Again, it is very cool technically, but it contradicts declared goal: to make new computer kit for beginners.IMHO, it is doesn't matter for novice, what to solder, SOIC8 or SOIC28. SOIC28 is as easy (or hard, if you want) as SOIC8.And larger chip could make much more useful computer: it will be possible to add some minimal sound (as such chips typically have DAC), keyboard, and, maybe later, true monitor output in VGA style (not DP or HDMI of course).It will be not much harder (if at all) to solder, but could be good base for expansion if owner gain interest in such things.
• _Microft
  Thanks, this was very insightful and entertaining once again!One thing: you might want to mention the required board thickness (0.8mm, iirc?) for people planning to have their own boards made.Edit, explanation for others: that is required to make the "USB-C edge connector" fit the plug.
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  kibwen
  Excellent article, thanks. At the risk of missing the forest for the trees, I wonder how much simpler things would have been if you had been slightly flexible on the 8-pin requirement. It seems as though having just a few more pins would have reduced the complexity of the project significantly while only marginally increasing the time it takes to solder.
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  alnwlsn
  It's almost 2 chips. One is just a USB-serial IC! But you didn't count the SD card, so you're up to 3 again.Total pin count is so low on this, I'm very tempted to make a dead bug version.
• blacklion
  It is interesting how to go to the limits of low-end author needs to implement CPU emulator. It is not obvious, that you need ADD layers at this level, not REMOVE them!
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  tromp
  > but I am allergic to RISC-V for personal reasons.Do you mind elaborating?
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  myself248
  I have the perverse urge to forego even the board, and just make this a circuit sculpture.
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  zokier
  I think it would be cute to also use 8 pin SPI flash chip instead of SD card for storage.
• kragen
  Aside from the project itself being very cool, this page is a great source for information about small microcontrollers, even if it does omit the WLCSP ones. And it links to the MIPS emulator page for ARM at https://dmitry.gr/?r=05.Projects&proj=33.%20LinuxCard which seems very interesting.
• thedanbob
  I've dabbled in microcontrollers and enjoy how the limitations force me to find creative solutions, but this is truly next level. I'm not great with a soldering iron but I'm seriously considering assembling one of these.
• sim7c00
  super fun read thanks. cool result too :)! also love all the different options for hw discussed in lot of details. thx!
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  FirmwareBurner
  I knew it was gonna be dimitry from reading the title
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  classichasclass
  This pleasantly reminds me of the little 6502 or 1802 Altoids-tin computers you can buy and assemble, but arguably more "useful" (though I get a lot of use out of a 6502 ;-).
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  coupdejarnac
  Under parts selection.. Even considering the PIC 16F. Why.
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  rhelz
  Was there no native ARM linux you could have used? As I recall, you have used this emulated MIPs technique in many of your published projects, so it's good to prove that the hardware is working?Or why not just go full native....grab some MIPS-core IP and make your own with an FPGA?
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  yapyap
  > There was a time when one could order a kit and assemble a computer at homeI think I get what OP means but you can definitely order a pc kit and just assemble it nowadays
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  dvh
  Please tell me you didn't use ENIG for the USB connector. It would be sacrilege.
• curtisszmania
  [dead]