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Thread: First board design - Teensy LC as thermometer brain. Board layout input?

  1. #1
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    First board design - Teensy LC as thermometer brain. Board layout input?

    Hello all,

    Awhile back I started work on a project to make a homemade internet-connected barbecue thermometer to address the shortcomings of commercially available units.

    I prototyped the device on an Arduino Uno + Raspberry Pi B+, and am now working on building a unit based on a Teensy LC and an ESP8266 (ESP-WROOM-02) module, with the goal of having the unit last 24 hours on 2xAA batteries.

    This is the first time I have laid out a board, and while I did a lot of research, I would appreciate anybody who could take the time to offer feedback and suggestions for improvement.

    A couple of notes:
    • I placed the Teensy where I did to accommodate the placement of other items on the board while still allowing accessibility to the USB port for code updates. Obviously it made trace routing a bit hairy but I think it worked out.
    • I'm intentionally trying to stick with PTH components (the castellated ESP module being the notable exception) because my soldering skill is still pretty novice-level and my equipment is abysmal.
    • I did read several places about having separate ground planes for analog and digital; however, the Teensy LC does not appear to have a distinct AGND port like the other 32-bit Teensy's, is this worth the effort? Also, the signals I'm sampling are low (read: no) frequency.


    Thanks for your feedback!


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  2. #2
    Senior Member PaulStoffregen's Avatar
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    Single GND is probably fine for this project. But if possible, try to route the analog ground signals separately from the digital GND lines. The power to the ESP in particular will be substantial when it's transmitting, so you want to keep that ground wire separate from the ones connecting to the sensors.

  3. #3
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    Quote Originally Posted by PaulStoffregen View Post
    Single GND is probably fine for this project. But if possible, try to route the analog ground signals separately from the digital GND lines. The power to the ESP in particular will be substantial when it's transmitting, so you want to keep that ground wire separate from the ones connecting to the sensors.
    Hey, thank you so much for taking the time to respond.

    Based on some additional feedback I received from another source, I decided to rethink my component choices a bit and have swapped out the Adafruit OLED module with a Sparkfun Teensyview, which allows me to get everything on the same side of the board and have a dedicated ground plane on the other side.

    So, in this scenario, everything is connected directly to the ground plane without signal traces (exception being the ESP module, which I have vias immediately next to the ground pins to pass through to the rear ground plane. (updated diagram attached)

    Is this sufficient? Or should I add a separation to the ground plane under the ESP and route that back to the supply module separately?

    Thanks again, I really appreciate it!

    (obviously, also decided to kill the USB port access and just open the case if needed)

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