Custom Atmega328P PCB

A custom Atmega328P PCB with a built-in 8Ch Logic level converter, as well as some other practical enhancements to make prototyping easier.

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While working on my MCU-8266-12E IoT controller board, I wanted to add an expansion card, that could be completely flexible in its operation. It should not have only one dedicated function.

I decided on using the APE protocol in ESPHome, where they use a standard Arduino board, connected with I2C to add additional Inputs and Outputs to an ESP device.

I also decided that, since I will be designing a PCB anyway, I will add a built-in logic level converter on the board as well.
As the board would basically be programmed only once, in my final version, I will get rid of the USB port, and just use ICSP to flash it.

Additional 5v and 3v ports, and two dedicated multi-connection busses, ( mainly for connecting i2c devices was also added. ( I also added a dedicated 3v LDO regulator, to provide a bit more current for use with hungry devices like LoRa radios etc that requires 3.3v to operate

Initial Design

The PCB is loosely based on the Arduino Nano. All GPIO pins will thus follow Arduino Labeling.

Page 2 will deal with the Logic Level Converters

Page 3 is for the USB to Serial converter

  • Manufacturing of the PCB - @ PCBWay

    MakerIoT202001/19/2022 at 13:00 0 comments

    This PCB was manufactured at PCBWAY. The Gerber files and BOM, as well as all the schematics, will soon be available as a shared project on their website. If you would like to have PCBWAY manufacture one of your own, designs, or even this particular PCB, you need to do the following…

    1) Click on this link
    2) Create an account if you have not already got one of your own.
    If you use the link above, you will also instantly receive a $5USD coupon, which you can use on your first or any other order later. (Disclaimer: I will earn a small referral fee from PCBWay. This referral fee will not affect the cost of your order, nor will you pay any part thereof.)
    3) Once you have gone to their website, and created an account, or login with your existing account,

    4) Click on PCB Instant Quote

    5) If you do not have any very special requirements for your PCB, click on Quick-order PCB

    6) Click on Add Gerber File, and select your Gerber file(s) from your computer. Most of your PCB details will now be automatically selected, leaving you to only select the solder mask and silk-screen colour, as well as to remove the order number or not. You can of course fine-tune everything exactly as you want as well.

    7) You can also select whether you want an SMD stencil, or have the board assembled after manufacturing. Please note that the assembly service, as well as the cost of your components, ARE NOT included in the initial quoted price. ( The quote will update depending on what options you select ).

    8) When you are happy with the options that you have selected, you can click on the Save to Cart Button. From here on, you can go to the top of the screen, click on Cart, make any payment(s) or use any coupons that you have in your account.

    Then just sit back and wait for your new PCB to be delivered to your door via the shipping company that you have selected during checkout.

  • PCB Design and Manufacturing

    MakerIoT202001/19/2022 at 12:56 0 comments

    The PCB is a double layer, with SMD components, mostly in 0805 sizes. 

    Some features of the PCB:

    All GPIO Pins are clearly marked on the silkscreen.

    The Logic level converters are (for this version at least) fixed to 3.3v on the LV side and 5v on the HV side. No additional power source is needed to use the converter. Logic level conversion is bi-directional, with a total of 8 channels. 

    The 3v LDO regulator can be powered from the 5v input, or directly from VIN, by changing the position of a jumper.

    Additional Power ports (5v x 4), (3.3v x 4) and (GND x 8) is provided at the bottom of the PCB.

    G1, and G2 are two separate bus connections, mainly put there to provide a way to connect various I2C devices together, but as these ports are not physically connected to anything else on the board, they can also be used for other purposes...

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