Forum Rule: Always post complete source code & details to reproduce any issue!
Results 1 to 5 of 5

Thread: What to add for general purpose Teensy board?

  1. #1
    Senior Member
    Join Date
    May 2015
    Posts
    442

    What to add for general purpose Teensy board?

    I am thinking of trying out JLC SMT assembly service and I am looking for ideas on what to add to a general purpose board the Teensy would plug into. 3.3v regulator powered from the usb 5v on the Teensy pin, a few rail to rail op amps with jumper selectable gain, I2c OLED display, and some stemmaQT connectors are on the list. Any ideas on what you would want to have if you were making one to make solderless breadboard projects faster to prototype? The board can be up to 100 mm sq for the same price if it stays 2 layers so I have some room to play with. Would header with the spi connections and a few cs lines be a must have for you? Are the boards with a ground, Vcc, for each i/o useful?

    Any suggestions welcome. Kicad project files will go up on a public gethub if I get a version I like.

  2. #2
    Senior Member
    Join Date
    Nov 2015
    Location
    Cold hollow VT
    Posts
    204
    My general purpose Teensy widget utilizes a T3.2, a choice of either ILI9341 or 20x4 TFT display, an SD-Card socket, and optional PB switches. I bring out 6 IO lines 1x analog output and I2C communications with 5v and 3.3v power onto a 2x8 berg header to allow off board devices. It has evolved over time to add a 2500mAhr LIPO battery and charger for making portable devices. The battery fits nicely between the PCB and display. The ILI9341 version fits nicely into a 3D printed case.

  3. #3
    Senior Member+ MichaelMeissner's Avatar
    Join Date
    Nov 2012
    Location
    Ayer Massachussetts
    Posts
    4,090

    Cool

    It kind of depends on how big you want the boards, which Teensy is the base, whether you would be starting with the Micromod board or the normal 28 or 48 pin Teensies.

    I tend to like to have pinouts grouped logically so that you can easily plug in the 4 wires for serial connections, several I2C connections like you have planned, two separate SPI connections (on Teensy 4.1), etc. For the I2C connections, add 2.2K pull-up resistors. Some I2C devices have a 5th pin for interrupt, but unfortunately the normal QWIC connectors only have 4 pins. I also like adding a pin for bringing out VIN for the serial and I2C connections in case the user needs to add level shifters to convert to a 5V bus. For the Teensy 4.1, bring out the USB host and ethernet pins so these are accessable even if other boards are stacked on top of the Teensy. Depending on board space, for the other Teensys consider bringing out some of the underneath pins.

    Here is the design that I did the last time I was designing it. Unfortunately, I never finished soldering all of the wires to finish the breakout board:
    • Prototype board it is designed around: https://www.tindie.com/products/draz...roject-boards/
    • Layout: http://www.the-meissners.org/tmp/202...4.1-layout.pdf
    • Bring out Serial1, PWM, or CAN (pins 0, 1, ground, 3.3v, vin);
    • Bring out Serial3, PWM, S/PDIF, or A0/A1 (pins 14/A0, 15/A1, ground, 3.3v, vin);
    • Bring out I2C1: (pins 18/A4, 19/A5, ground, 3.3v, vin, and pin 4 for using as the interrupt pin);
    • Bring out one button with pin 3;
    • Bring out another button with a jumper;
    • Bring out two leds, each of which is connected with a jumper;
    • Bring out I2S1: (pins 6, 7, 20/A6, 21/A7, 23/A9, ground, 3.3v, vin);
    • Bring out analog pin #1 (pin 22/A8, 3.3v, ground);
    • Bring out analog pin #2 (pin 16/A2, 3.3v, ground);
    • Bring out SPI0 (pins 11, 12, 13, 36, 37, 38/A14, 39/A15, ground, 3.3v, vin);
    • Bring out SPI1 (pins 26, 27, 28, 29, 30, 40, 41/A17, ground, 3.3v, vin);
    • Bring out one pin to a SN74AHC1G125DBVR level shifter for neopixel (pin 35, ground, vin);
    • Bring out one pin to a SN74AHC1G125DBVR level shifter for neopixel (pin 17/A3, ground, vin);
    • The SPI pins for 2 CS pins, D/C, and Reset are connected via a switch to control whether the default pin is used or you set the pin via a jumper;
    • The neopixel pins are each connected via a switch to control whether the default pin is used or you set the pin via a jumper.


    The idea is each of the serial, SPI, and neopixel pinouts are in the same order, so I can make a custom cable that matches an individual display, etc. to the pinout.

    I tend to use the custom jumper wires with pre-crimpted wires to make my own custom dupont cables that I get from pololu.com:

  4. #4
    Senior Member
    Join Date
    May 2015
    Posts
    442
    Thanks Frank. I will try to include as many of these as I can fit in 10cm sq. I like the pre-crimped wire but the ones I have are ribbon cables but those should hold up much better.

    I am not sure yet if I want to break out the bottom side smt pads. I am going that on a board for work mainly because I need the 2nd I2C interface.

  5. #5
    Senior Member
    Join Date
    May 2015
    Posts
    442
    Quote Originally Posted by grease_lighting View Post
    My general purpose Teensy widget utilizes a T3.2, a choice of either ILI9341 or 20x4 TFT display, an SD-Card socket, and optional PB switches. I bring out 6 IO lines 1x analog output and I2C communications with 5v and 3.3v power onto a 2x8 berg header to allow off board devices. It has evolved over time to add a 2500mAhr LIPO battery and charger for making portable devices. The battery fits nicely between the PCB and display. The ILI9341 version fits nicely into a 3D printed case.
    Good choices Which chip you use for LIPO management? I have a few 18650's but they are junk. Rated 10,000 mah but test about 1000 or less. You can't even test them with a load under about 10 ohms or they just drop to nothing instantly. I do have some 900ma I hope are close to their spec. I like the little tiny displays for their low cost myself but a I can read the ILI9341 without glasses so there is that. B)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •