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Schematic Checking — Parallax Forums

Schematic Checking

ThricThric Posts: 109
edited 2011-09-15 16:07 in Propeller 1
Before I send in my PCB to the fact. I was wondering if someone could check over my programming USB port connection. Since its pretty important It would be great if come heads up can be given.

Here is the datasheet for the CP2102 that i'm using for USB to UART: http://www.sparkfun.com/datasheets/IC/cp2102.pdf

Thanks
USB schematic.jpg
1024 x 576 - 42K

Comments

  • TtailspinTtailspin Posts: 1,326
    edited 2011-09-15 07:55
    Yes, very bad practice to cross over parts like that, A good knuckle rapping with an Inventors wand would serve to teach...

    Also, you would want to post the PCB art along with the schematic,
    That way we can help check to see if they are one in the same, Often they are not...:tongue:

    -Tommy
  • LeonLeon Posts: 7,620
    edited 2011-09-15 08:48
    Most PCB software checks that the schematic and PCB match each other.

    Also, use symbols for the supply and ground connections with a symbol on each pin.

    You don't seem to have any decoupling capacitors.

    R12 is too large.

    You need a regulator if the Propeller is powered from the USB supply.
  • smbakersmbaker Posts: 164
    edited 2011-09-15 10:12
    I don't see anything connected to the prop's VSS pins, other than BOEn.

    If you're using EAGLE to make this (it looks kinda like it to me), then you can find power symbols for +3.3V and GND in the 'supply' library. Rather than connecting power from one chip to another, use individual symbols at each chip. Make sure all power pins are connected. As others have said, include bypass caps too.

    I suspect we're only seeing a partial schematic here, so maybe some of these items (bypass caps, power pins, etc) are addressed on the full schematic but we're not seeing them here.
  • ThricThric Posts: 109
    edited 2011-09-15 14:04
    Sorry about the bad schematic :-/ too bad they don't teach these things in high school. I'm still trying to find a way to organize my schematics from the rats nest it usually is, trust me that this is a large improvement from my previous ones :).

    @smbaker: You're right this is only a small segment, i placed the bypass capacitors in a different part of the schematics.

    @Leon: Thanks for the catch of the resistor. I"m not going to be publish this schematic for anything so i know what values of the parts are. There is also a separate regulator for the propeller and other parts of the board.
  • smbakersmbaker Posts: 164
    edited 2011-09-15 16:07
    Thric wrote: »
    Sorry about the bad schematic :-/ too bad they don't teach these things in high school. I'm still trying to find a way to organize my schematics from the rats nest it usually is, trust me that this is a large improvement from my previous ones :)

    Don't worry, I learned more browsing Radio Electronics and Byte magazines than I ever learned in High School! (and the Internet and forums like this are a far better resource than those magazines were back in the 80s). It's just a matter of practice, playing with the software, and you'll pick up how to make expert schematics.

    Also, labeling parts on the schematic is always a good idea. You might know what the parts are today, but a couple years from now when you're looking at the schematic, it will be handy to have a reminder. More than once I failed to label a part with the right value because I was in a hurry, only to end up stuffing the PCB with the wrong part later. The same goes for labeling headers and connectors and such on PCBs.
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