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SAO Adapter for Voja4 Badge

Hardware add-on to enable Voja4 to speak I2C with a full-featured 6-pin SAO socket.

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The SAO Voja4 is a hardware adapter which enables the Voja4 Badge to offer full 6-pin SAO compatibility including I2C and GPIO 1&2 or UART.

This adapter also includes [untested] hardware provisions for SPI with additional OLED and SD Card Headers. Hopefully a color OLED or SD Card can be enabled!

Learn more about the Voja4 Badge!:
https://hackaday.io/project/188025-2022-hackaday-supercon-6-badge-guide
https://www.crowdsupply.com/files/f289/37916991-2888-466f-b6e9-b5ae9045f289/teardown-2024-nathan-jones-voja4.pdf

Buy a Voja4:
https://www.tindie.com/products/0xc0decafe/supercon-2022-badge-voja4/

Using discrete transistors, we aim to enable I2C communication through an SAO port adapter board. This is a pass-through adapter - it does not have it's own I2C address. It only provides the I2C electronic protocol signals, with correctly driven I/O lines on the Voja4.

Reaching even further, we should be able to offer SPI communication, eventually, as well.

Several solder jumpers are built-in to keep thing flexible for the prototype.


HOW TO USE

Review the schematic to get more familiar with the features. There is also the relevent section of the badge I/O schematic embedded in the adapter schematic.

The general idea is that if you want to use SPI stuff, you have to close the jumpers in the SPI ZONE. And if you want to use I2C, close the ones in the I2C ZONE. Choose one or the other. Both modes are not available at the same time.

If you want alternate power input to the badge and SAO with the 3V3 regulator, connect the battery and close the jumper in that zone. And remove the batteries from the badge!

Finally, if you want to use the GPIO1&2 of the SAO port, close the associated pads at the top, selecting either input or output modes.

Example code will be added in the project page at Github as it becomes available. 

SAO Voja4 Adapter V1 Schematic.pdf

SAO Voja4 Adapter V1 Schematic

Adobe Portable Document Format - 479.97 kB - 10/23/2024 at 13:59

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  • Protoype Boards Ordered

    Andy Geppert10/23/2024 at 04:56 0 comments

    I hope I didn't make any major mistakes because they are ordered!

    If the SPI ends up working, this should be compatible with at least two Adafruit products:

    1.5” 128x128, 16-bit color w/MicroSD holder: https://www.adafruit.com/product/1431

    MicroSD Card Breakout Board: https://www.adafruit.com/product/4682

    These should arrive just before I depart to Supercon!

  • Design Ready

    Andy Geppert10/22/2024 at 14:02 0 comments

    Although Koppany has only proven the hardware concept with a Pico W at this point, we have enough confidence to move forward with a design for prototyping. Oh, AND, there are schedule pressures so let's build some fast!

    I need to finish the routing, but the layout will be similar to this and even fits the SAO Contest size limits!

    Hoping to have these available for testing at Supercon 2024 so bring your Voja4!

  • Brainstorming solutions

    Andy Geppert10/22/2024 at 13:57 0 comments

    You already know the input/output cabability of the Voja4 badge is constrained. But is there enough hardware and simulated-4-bit-CPU hardware to enable I2C or even SPI communication? We are going to find out!


    Some GPIO-based discrete hardware solutions:

    • Two transistors, double NOT, to create open collector mode.
    • Is there a better way to make use of the discrete INPUT/OUTPUT signals for I2C?

    ^^^ This is looking like the right solution. Koppany has a proof-of-concept running on a breadboard, driven by a Pico W. Next step is to port the code to Voja4. I'm working on a schematic/board update that I should be able to get before Supercon. I hope!!!

    UART or GPIO to I2C MASTER/HOST:

    • Program an 8-pin MCU to be the bridge controller.


    UART to I2C MASTER/HOST:


    I2C [slave] to UART:

    Is there a dedicated chip that does the job? Perhaps using a tiny 8-pin MCU is an option.

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