Hot!Designing a custom board for PIC18F4550

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Flipp3rix
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2019/03/24 08:56:34 (permalink)
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Designing a custom board for PIC18F4550

Hi, now I'm designing a new custom PCB for PIC18F4550. I have attacched in this post my current schematics and my current pcb board design.
A """feature""" that I added is a 10KOhm resistor for every pin(as pull up resistor)
Any opinion and suggestion is welcome.

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#1

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    1and0
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    Re: Designing a custom board for PIC18F4550 2019/03/24 09:42:52 (permalink)
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    Flipp3rix
    A """feature""" that I added is a 10KOhm resistor for every pin(as pull up resistor)
    Any opinion and suggestion is welcome.

    Why all the pull-ups?
    #2
    Mysil
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    Re: Designing a custom board for PIC18F4550 2019/03/24 10:42:10 (permalink)
    +1 (1)
    Hi,
    Not unreasonable as a exercise to getting familiar with PCB layout tools and Gerber files.
    But a new board design for an obsolete chip?
     
    Image of the layout, do Not show footprint for decoupling capacitors!
    0.1 uF Ceramic capacitors,  25 V or 50 V, one each side of the package.
    These must be put in place, right next to the package.
    Connecting decoupling capacitors to the pads along the edge of the board, is not acceptable.
    Curiosity HPC board also use 1.0  uF capacitors in parallel with 0.1 uF.
     
    8 bit PIC devices in 40 pin package are mostly pin compatible,
    so your board layout may be useable also for other devices in 40 pin PDIP package,
    like PIC18F45K50 with USB,
    or for devices without USB, like PIC18F45K22, PIC18F46K22, PIC18F46K40, or PIC18F47K42.
     
    Some of the newest PIC devices have internal pull-ups for all pins.
     
    You have selected a device with USB.
    If you are going to use USB communication, be aware that there may be some additional layout requirements for USB traces, and maybe try to design a USB connector into the layout.
     
    Curiosity HPC board DM164136, is able to place layout and socket for 28 pin device inside the 40 pin layout.
     
        Mysil
    post edited by Mysil - 2019/03/24 10:48:55
    #3
    Flipp3rix
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    Re: Designing a custom board for PIC18F4550 2019/03/24 11:16:30 (permalink)
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    Mysil
    Hi,
    Not unreasonable as a exercise to getting familiar with PCB layout tools and Gerber files.
    But a new board design for an obsolete chip?
     
    Image of the layout, do Not show footprint for decoupling capacitors!
    0.1 uF Ceramic capacitors,  25 V or 50 V, one each side of the package.
    These must be put in place, right next to the package.
    Connecting decoupling capacitors to the pads along the edge of the board, is not acceptable.
    Curiosity HPC board also use 1.0  uF capacitors in parallel with 0.1 uF.
     
    8 bit PIC devices in 40 pin package are mostly pin compatible,
    so your board layout may be useable also for other devices in 40 pin PDIP package,
    like PIC18F45K50 with USB,
    or for devices without USB, like PIC18F45K22, PIC18F46K22, PIC18F46K40, or PIC18F47K42.
     
    Some of the newest PIC devices have internal pull-ups for all pins.
     
    You have selected a device with USB.
    If you are going to use USB communication, be aware that there may be some additional layout requirements for USB traces, and maybe try to design a USB connector into the layout.
     
    Curiosity HPC board DM164136, is able to place layout and socket for 28 pin device inside the 40 pin layout.
     
        Mysil




    Can you suggest me a modern chip with integrated usb and pull ups?
    #4
    katela
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    Re: Designing a custom board for PIC18F4550 2019/03/24 11:24:48 (permalink)
    +1 (1)
    You didn't say the reasons for your "Feature" to get suggestions.
    As Mysil has said, what are the reasons to design your new board using an ancient PIC while there are alternative cheaper and more powerful like the PIC18F45k50 for example?
    post edited by katela - 2019/03/24 11:27:23

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    #5
    Aussie Susan
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    Re: Designing a custom board for PIC18F4550 2019/03/24 18:41:56 (permalink)
    #6
    PStechPaul
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    Re: Designing a custom board for PIC18F4550 2019/03/25 00:18:05 (permalink)
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    There is really no reason to add all those discrete pull-up resistors. Perhaps add pads and tracks for SIP resistor networks, which could be installed with the common pin either at Vss or Vdd for pull-ups or pull-downs. And without the resistors the pads can be used for jumper wires for prototyping.
     
    I would also suggest adding all the components needed to implement the PICdem FSUSB board which has working software based on MLA. So have a USB connector as well as the recommended resistors, capacitors, LEDs, ferrite beads, and protection devices. You might also add components and connectors to implement a USB-Serial link, I2C, and SPI for peripherals. And perhaps lay out the board for SMT components, and/or also a 28 pin DIP socket.

     
    #7
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