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abracm / display-latam

ESP32-based project to make a display for speedcubing timers. We seek to create an alternative to commercially available displays which is cheaper, lighter, open-source, repairable, and sustainable.
GNU Affero General Public License v3.0
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display-latam

ESP32-based project to make a display for speedcubing timers.

We seek to create an alternative to commercially available displays which is cheaper, lighter,open-source, repairable, and sustainable.

How to contribute

Take a look at the open issues on the repository to see how you can contribute. Open an issue for a request or suggestion. You can also send an email for contato@abracm.org.br for enquries, contributions, feedback, etc.

The language of the project is English to make it more accesible worldwide.

Please stick to the following best practices when contributing to this project:

Currently, the code is functional, but the documentation needs work, which makes it hard for communities to build their own version. The work plan is on the short medium term is:

  1. gather ideas and contributions for an Alpha release
  2. incorporate pull requests, contributions which are a short term priority
  3. prepare documentation, tutorials for the release of the Alpha version
  4. release the Alpha version, make easily available for communities to build and test out - can we do it by the end of August/start of September?
  5. work on improvements to the Alpha version, receive feedback from users
  6. create hardware specifications for a 1.0 version release (make hardware investments future proof)
  7. release 1.0 version of project, make sure future code updates are backwards compatible with the hardware

Features

TODO add video demo

Libraries setup

From Libs.zip, extrac Libs folder and copy it's contents to your Arduino/Libraries directory.

Software Installation guide

Software Installation guide:

  1. Install the Arduino IDE software from https://www.arduino.cc/en/software
  2. It should create a folder named “Arduino” in Documents, you want to create 2 folders, “display-latam”, and “Libraries”.
  3. Download the Libs.zip file from the GitHub, extract the zip file, and then place all of the folders in the zip file to the “Libraries” folder. image
  4. Place the “display-latam.ino”, “xantofont.cpp”, and “xantofont.h” files in the “display_latam folder. image
  5. Click on the display-latam.ino file to open it up in Arduino IDE.
  6. Connect your board to your computer with USB, the official Arduino website has more detailed instructions on this. I actually had a lot of trouble with this initially, my solution was to just try every USB port until one worked. https://support.arduino.cc/hc/en-us/articles/4406856349970-Select-board-and-port-in-Arduino-IDE
  7. Press the upload button and wait for it to upload. You also need to use a USB cable that is capable of transmitting data (some USB cables have power only) or it will not be able to upload.

image

  1. It should finish uploading successfully and the console should look like this when it is finished. The display should be ready for usage now. image

installation, how to build

TODO

Draft preview of the project (using the acrylic covers) draft_preview

Schematics for the ESP32 C3 mini are as follows:

schematics_esp32_c3_mini

Schematics for the ESP32 S2 are also available at doc/schematics_esp32_s2.jpg

Parts list

Two alternatives for encasing the hardware:

Materials/type Details
  • 3mm polycarbonate sheet
  • Chicago screws that are 25mm long and 5mm in diameter
  • Spacers of 5mm in diameter with a length according to the LED matrix you have. If the display has sockets, you need spacers four 7mm long spacers and four 10mm long ones. If the display is soldered, you need eight spacers with a length of 8.5mm.
  • tint for contrast
 cutout for CNC available on doc/acrylic-cover.skp, see doc/prototype_demo.skp for demo on how to build
3D printed case draft design available on doc/draft_case.stl (WIP)

For power, you could use:

For the display stand, you could use the 3D-printed stand available on doc/stand.stl.

Current estimates for the cost of the materials for a display are of around USD ~20 (buying supplies off China e.g. Aliexpress).

Contributors

We are specially greatful to Fabio Seiji Massui 2013MASS01 for kicking off this project and inspiring us to pursue the goal of developing an open-source and cheap alternative to commercial displays.

Other contributors include:

Speedstacks timer signal protocol

The Speedstacks timers send a digital audio signal thorugh the data port (example). This is a guide how on to interpret the signal.

The timer sends the signal with a fixed rate of 1200 bits per second (check if this is correct and consistent across all timer generations). It sends a packet that are 90 or 100 bytes long to convey a single time to be displayed.

Idle values

The bitstream user a standard idle value (0 or 1) to inform when a byte or a packet ended. The idle value varies across timer generations (see section below on timer generations).

Each byte is proceeded by a non-idle value, to show that the byte has begun, and followed by an idle value, to show that it has ended.

Gen 3 example of a Gen 3 timer bitstream- the idle value is 1

Gen 4 example of a Gen 4 timer bitstream- the idle value is 0

Each packet is separated by an unspecificed number of idle values (check if we can tell an exact amount and if it is consistent across timers). Therefore, to check if a packet has ended, you just need to check if you can read ten or more equal values in a row, as that couldn't happen if a byte was being transmitted.

Packets

A time to be displayed is sent as a packet that can be 9 or 10 bytes long. The lenght of the packet is determined by the timer generation (see section below on timer generations).

Because of the non-idle value and idle value that go before and after each byte, the bytes take 10 bits to be transmitted, and the packet lenghts are therefore 90 or 100 bits.

Here is an example of a full packet extracted from a Gen 3 timer that will use to break down what each byte means. TODO

Notice that this packet it 10 bytes long and uses 1 as its idle value.

These are what each byte consists of:

byte 1: state of the timer

The first byte is an ASCII code for one of the following letters, which represent the state the timer is in:

byte 2-6 or 2-7: time itself

These are the bytes that convey the time information. Byte 7 may or may not be a part of this depending on the timer generation (see section below on timer generations).

Here is the breakdown on byte-by-byte:

The byte represents the ASCII code for the digit, which is the digit + 48

3rd to last byte: checksum

This byte is a checksum of the previous bytes (2-6 or 2-7), to ensure the reading is correct.

It it the sum of the values (not the ASCII codes) of all digits + 64.

2nd to last and last bytes: unnecessary line breaks?

These bytes are the ASCII codes for \n (newline) and \r (carriage return). Is this just useless?

Processing a byte

After reading the 10 bits necessary for a byte (non-idle value + byte + idle value), you must first discard the 1st and the last bits of the byte.

Then, you must place the bits in reverse order. E.g. (11001001 becomes 10010011)

Finally, the bits must be inverted to arrive at the final byte (10010011 becomes 01101100). do timers with a 0 idle value also need to be inverted?

Example of interpreting a packet from start to finish

WIP

Speedstacks timer generations

Generation 3

Gen 3

Generation 4

Gen 4

Generation 5

Gen 5

can we easily support other non-speedstacks timers? testing needed

Useful sources

Migrating an Arduino board to a standalone microcontroller on a breadboard