Please review my project: an 8031 SBC
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Skip Tavakkolian 1 week ago
Hello, This is my first ever attempt at schematic capture and PCB layout.  It would be great if I could get some feedback, critique or any helpful comments about errors, etc.  I'm not sure if I got the grounding right and also not sure if leaving unused pins unconnected is ok (though several threads in the forum seem to say it is). Can the board be made simpler? (only for 8031's).  FYI, I've not built a breadboard version, but the schematics I used for reference look correct on paper. Here's the project: [https://easyeda.com/skip.tavakkolian/8031sbc](https://easyeda.com/skip.tavakkolian/8031sbc) It is not my design; it's actually a modification of the following two designs I found on the net: [https://www.dos4ever.com/8031board/schema.pdf](https://www.dos4ever.com/8031board/schema.pdf) [http://sfprime.net/i8031/8031dip.pdf](http://sfprime.net/i8031/8031dip.pdf) Background: I salvaged a number of 8031's a while back and would like to build a few SBC's with them (primarily to run Forth).  I initially searched EasyEDA hoping somebody had already done it but, as far as I could tell, no one has.  I found the above two designs -- which are fairly similar -- and used them to create the schematic. I used the Auto Router.  I found a couple of EasyEDA tutorials on YouTube that were very helpful (Great Scott was one).  My end goal is to build a few Forth SBC's. Thanks, -Skip
Comments
andyfierman 1 week ago
Have you read (2.2) and been through the checklists (4) and (6) in (2) in: [https://easyeda.com/forum/topic/How-to-ask-for-help-and-get-an-answer-71b17a40d15442349eaecbfae083e46a](https://easyeda.com/forum/topic/How-to-ask-for-help-and-get-an-answer-71b17a40d15442349eaecbfae083e46a)
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Skip Tavakkolian 1 week ago
I have not. Thanks for the references.
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andyfierman 1 week ago
Except for U3 you have no power supply decoupling capacitors. Please see: [https://easyeda\.com/andyfierman/Power\_supply\_decoupling\_and\_why\_it\_matters\_\-451e18a0d36b4f208394b2a2ff7642c9](https://easyeda.com/andyfierman/Power_supply_decoupling_and_why_it_matters_-451e18a0d36b4f208394b2a2ff7642c9) You also need to at least increase the width of the ground and power tracks. Better still use copper areas (a.k.a. floods) for maximum copper for power and ground. Move the crystal components, C5, C6 and Y1 closed to the associated pins on U3. Pins on devices can only be left unconnected if they are outputs or if they are inputs that have internal pull ups or pull downs. Please read the device datasheets carefully for information about this.
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Skip Tavakkolian 1 week ago
Thank you!  It's a steep learning curve, but the material helps a lot.
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temporary 1 week ago
I would add: * Use the design manager (for the schematic and PCB) and heed the warnings (i.e. as above use the X for assigned pins). * Check that the ICs have correct pin assignments (yes, incorrect assignments happen too often). * Suggest mounting holes in each corner (I also like to bevel the corners). * Remove the overlapping traces (i.e. the red dot that in on the trace when it does not appear to be an intersection). * Finally, the hole diameters for the EPROM are too small if you want to use a ZIF socket. (recommended as you will need to insert and remove the EPROM many times if you are writing your own monitor or code). AlanX
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andyfierman 1 week ago
As advised in the documents referred to above, search for and use the schematic symbols already in the library for the holes so that they get pulled into the PCB. :)
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