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Replacement suggestions for the SX28 surface mount (or DIP) microcontroller — Parallax Forums

Replacement suggestions for the SX28 surface mount (or DIP) microcontroller

Been a while since I've had time to work on many new electronics and robotics projects! Finally getting some time to catch up where I left off.


One project used a surface mount SX28 chip. Unfortunately those now seem to be completely unavailable and I'm sure not recommended for new designs. Sad because I really liked those chips.


So I am looking for something similar to that processor. Some features desired are:


  • 5V friendly I/O pins and supply
  • SSOP28 or similar package
  • At least 16 available digital I/O (more preferred)
  • Built in serial UART ideally using additional pins
  • Simple clocking: External Resonator, Internal, or Crystal (was running at 4Mhz (faster ok)
  • Don't need a ton of memory. Was getting by with 2K flash and 136 bytes of RAM. More is fine!


I don't think Parallax directly offers any equivalent parts. While I think the Propeller is awesome it doesn't seem to fit for this project.


Anyone switch from the SX28 to a different chip? What did you use and what tools are available?

Comments

  • PublisonPublison Posts: 12,134

    I still have a good quantity that you sold me. PM me

  • jmgjmg Posts: 14,820
    edited 2021-01-25 19:03

    @RobotWorkshop said:
    So I am looking for something similar to that processor. Some features desired are:
    5V friendly I/O pins and supply
    SSOP28 or similar package
    At least 16 available digital I/O (more preferred)
    Built in serial UART ideally using additional pins
    Simple clocking: External Resonator, Internal, or Crystal (was running at 4Mhz (faster ok)
    Don't need a ton of memory. Was getting by with 2K flash and 136 bytes of RAM. More is fine!

    If you need 5V supply, and 16io, then there are a lot of 8051 variants in the '003' pinout, that will give you a multi-sourced supply cushion too. More are coming all the time.
    Some examples here https://www.nuvoton.com/products/microcontrollers/8bit-8051-mcus/industrial-8051-series/
    Eval boards are here https://direct.nuvoton.com/en/8051-tool/
    Also this is coming https://www.silabs.com/community/mcu/8-bit/forum.topic.html/efm8bb51_and_efm8bb52-9rsK

  • Would you want to stick with the PIC ISA? I don't think you could go past this one then?
    PIC16F18857-I/SS - 56KB Flash 4KB RAM 256B EE CIP 32MHz internal osc. - and cheap

  • It's good to see there are still a bunch of familiar names on the forums after I've had such a long sabbatical from my projects.

    My original program was written in SX/B for an SX28 chip. I used most of the I/O pins but could probably cut that down a little. I could easily convert to C or another language if I have to. I haven't rules out using SX28 surface mount chips and one last small run of custom boards using them. Just want to see what other options are out there since if it works out well I'd rather not redo everything again.

    Robert

  • I should also ask about any stashes of SX28 surface mount chips left. Anyone hiding a bunch? I don't think this is going to be a high volume project so I'd be happy to do one last board design using the SX28 surface mount chips since everything else is already done (schematic, code, etc)


    Maybe Parallax will do some early spring cleaning and find a bunch that were forgotten about......


    Robert

  • I think that PIC could work out well. I'd just have to port over my SX/B code to their C. That may be the route I go. Still if I find some SX28 stock I may do an initial version and small run of those and move to a PIC later. Will let me get something done sooner and give me time to port over my code to another chip.

  • bruceebrucee Posts: 238
    edited 2021-01-30 21:22

    Why not an ARM, lots of tools, lots of vendors, future path?


    NXP, STmicro and TI (maybe others) offer 5V tolerant IOs, internal oscillator (1%), much more memory, UARTs. Most running 30-50 MHz range, low power...


    A quick look at Digikey shows around 100 alternatives in small SO packages.


    Just noticed Cypress parts use a 5V supply, (internal regulator) and with that 5V IOs

  • I just today had need for a source of SX chips for the Stache BASIC Stamp programmer, following a long term commitment from a customer. Tapped the spigot at good old ebay. Found enough there of SX20AC/SS and SX18AC/SO to keep the product going for a while. I have boards laid out to use either of those chips, or SX28AC/SS.

    By the way, if you want the dip 28 version, SX28AC/DP, there are lots available there. Even one offer of new packages of 256 pieces on rails.

  • Good to hear a response from a familiar forum member! Glad to see that you're still here too!

    While I could use the DIP version I'd prefer the surface mount to conserve space. I'll probably try to use the SX28 for now since all the code will work as it is. I can always port to a new chip later of the project works out.

  • Just received from an ebay seller, 20 of the SX18AC/SO. I didn't think I'd see those again. They look so huge next to the /SS versions. Ubicom date code, February 2001. I know what you mean about sticking with working code. The code for the product was written by then BASIC Stamp/SX-forumista Steve Parkis, and I did the hardware side. There is no way I could or would want to translate that to another chip at this stage of the game!

  • MicksterMickster Posts: 1,890

    The Micromite has a few 5v tolerant pins:

    https://geoffg.net/MicromiteMX170.html

  • Freescale Kinetis series has quite a few variants with 5V-tolerant pins. MK20DX256 (used on the PJRC Teensy 3.2) is 5v-tolerant, and is plenty fast at 72MHz with an FPU.

    Otherwise, while you lose 5V tolerant IOs, the Propeller or Prop 2 might be a worthwhile way to go, with some (relatively easy) level translation circuitry, depending on what you want to do with it.

  • The 5V tolerance on the IO pins is a must. Anything that won't do that isn't really an option. I had looked at the Propeller chips early on and while those are awesome chips they don't really fit this particular application well at all. Besides the larger foot print the part that prevents at least the Prop 1 from being used is the startup latency and the external EEPROM storage. That old SX28 worked perfect with the 5V tolerant IO, quick startup, and enough RAM and Flash code storage all in a tiny package.

    I'd still like to find at least a small batch of surface mount SX28 chips so I can just use what I have already completed with no code changes. As it stands now I'm leaning towards the PIC line as a replacement. There is enough variety there to cover it and if I learn those tools it can help with other projects.

    There are a ton of great small microcontrollers out there but I don't want to invest the time for the learning curve in each one. Would rather just focus on a few to be expert in vs a bunch of watered down ones since there is only so much time to invest in other tools and as important all the quirks that are present in all the micros.

    The Propeller 1 is one I plan on keeping on my list and eventually will try the Propeller 2.

    Beyond that the Arduino has been great for small quick projects. Just trying to fill in the spot where I was using the SX chips.

    Had looked at the TI line but never really got into that. May eventually sell all that off. Some other projects I've been helping with use the PIC so I think that will end up being the next one to learn.

  • PublisonPublison Posts: 12,134

    PM sent.

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