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Just a quick check of microcontroller schematic before getting the PCB printed

Discussion in 'Microcontrollers, Programming and IoT' started by j4cobgarby, Apr 15, 2019.

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  1. j4cobgarby


    Sep 18, 2018
    Here's a schematic for a keyboard I'm designed (the actual keyboard keys aren't included in this screenshot, of course).
    Screenshot from 2019-04-15 18-34-10.png
    Does this schematic look reasonable? I've read that I can program the Atmega32u4 over the USB connection using the pre-programmed DFU bootloader, but just in case that doesn't work I've got 6 pins coming off the chip which I can use for the 6-pin ISP interface.

    I'd be very grateful if someone who's familiar with this microcontroller can look the schematic over quickly and give me any advice.

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Looks like the GND connection to the USB port is missing (or maybe the label GND is taken as a connection, but I prefer placing a dedicated GND symbol):

    Also: Vbus should only be connected to Vcc if the keyboard is powered from the USB interface.

    It is also good practice to add decoupling capacitor right next to the controller's Vcc pins (2, 14, 24). Use 100 nF ceramic type and make the connections to the µC as short as possible:
    one C between 1/2
    one C between 14/15
    one C from 24 to GND make the trace as short as possible, a GND plane would be best.
  3. Bluejets


    Oct 5, 2014
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