(Please note that is a forked repository. Details of the design are described at the very end of this README.md. Go to https://tinytapeout.com for instructions!)
This repo is a template you can make a copy of for your own ASIC design using Wokwi.
When you edit the Makefile to choose a different ID, the GitHub Action will fetch the digital netlist of your design from Wokwi.
The design gets wrapped in some extra logic that builds a 'scan chain'. This is a way to put lots of designs onto one chip and still have access to them all. You can see all of the technical details here.
After that, the action uses the open source ASIC tool called OpenLane to build the files needed to fabricate an ASIC.
When the action is complete, you can click here to see the latest build of your design. You need to download the zip file and take a look at the contents:
- gds_render.svg - picture of your ASIC design
- gds.html - zoomable picture of your ASIC design
- runs/wokwi/reports/final_summary_report.csv - CSV file with lots of details about the design
- runs/wokwi/reports/synthesis/1-synthesis.stat.rpt.strategy4 - list of the standard cells used by your design
- runs/wokwi/results/final/gds/user_module.gds - the final GDS file needed to make your design
The story of the wolf, goat and cabbage problem, quoted from wikipedia with some emojis added for later use in visualization:
A farmer (π§βπΎ) went to a market and purchased a wolf (πΊ), a goat (π), and a cabbage (π₯¬). On his way home, the π§βπΎ came to the bank of a river (γ°γ°) and rented a boat (πΆ). But crossing the river by πΆ, the π§βπΎ could carry only himself and a single one of his purchases: the πΊ, the π, or the π₯¬.
If left unattended together, the πΊ would eat the π, or the π would eat the π₯¬.
The π§βπΎ's challenge was to carry himself and his purchases to the far bank of the γ°γ° leaving each purchase intact.
The solution to the problem is known. However, this project wants to allow the interactive game of this puzzle.
Disclaimer: I have seen this logic puzzle been realized in plain hardware but I couldn't find it anymore! Any hints are welcome.
We define four input signals for every relevant object involved in the puzzle:
- F for the position of the farmer (π§βπΎ/π£)
- W for the position of the wolf (πΊ)
- G for the position of the goat (π)
- C for the position of the cabbage (π₯¬),
where
- a 0 means that the object is located on the left river bank and
- a 1 means that the object is located on the right river bank.
This allows us to use a slider switch for every input signal, so that we can visualize the object's location. As we will be working with Wokwi, the slider switch can be a Standard Single Pole Double Throw (SPDT) slide switch with three terminals:
The common terminal connects to an input pin of the ASIC (with an internal or external pull-up). The left terminal is connected to GND.
When the switch is in the left position, the ASIC pin is connected to GND which we define as logical signal level 0. The object the switch is related to (π§βπΎ/π£, πΊ, π or π₯¬) is on the left river bank.
When the switch is in the right position (right terminal being left unconnected), the signal is pulled high which we define as logical 1. The object the switch is related to (π§βπΎ/π£, πΊ, π or π₯¬) is on the right river bank.
Note TODO: Add example(s).
We want to let the player of the game know when they have won or lost.
The player has lost as soon as
- the πΊ and the π are left unattended (i.e. absence of the π§βπΎ) or
- the π and the π₯¬ are left unattended
because at least one of the objects would be eaten.
The player has won as soon as all objects (π§βπΎ/π£, πΊ, π or π₯¬) have reached the right river bank.
We can define the following outut signals to be relevant for the game play:
We define four input signals for every relevant object involved in the puzzle:
- L for the situation on the left bank being under control (no object-X-eats-object-Y situation), where 1 means "everything is fine" (βοΈ) and 0 means "situation is out of control" (β).
- R for the situation on the right bank being under control (no object-X-eats-object-Y situation), where 1 means "everything is fine" (βοΈ) and 0 means "situation is out of control" (β).
- E summary of the situations on both river banks (no object-X-eats-object-Y situation), where 1 means "everything is fine" (βοΈ) and 0 means "situation is out of control" (β). β Game is lost. βββ
- A as an indicator that all objects have reached the right bank of the river, where 1 means "yes" (βοΈ) and 0 means "no" (β). β Game is won! πππ
L and R are intermediate signals indicating on which side of the river a situation has occured why the player has lost the game.
There are some limitiations that are not covered by the current implementation, as described in a separate paragraph below.
We'll work with the following truth table with extended explanations:
| π§βπΎ/π£ | πΊ | π | π₯¬ | Scenario | Situation on the left bank under control? |
Situation on the right bank under control? |
Every- thing under control? |
All on the right bank? |
|---|---|---|---|---|---|---|---|---|
| F (in) | W (in) | G (in) | C (in) | L (out) | R (out) | E (out) | A (out) | |
| 0 | 0 | 0 | 0 | πΊππ₯¬π£ γ° | βοΈ | βοΈ | βοΈ | β |
| 0 | 0 | 0 | 1 | πΊππ£ γ° π₯¬ | βοΈ | βοΈ | βοΈ | β |
| 0 | 0 | 1 | 0 | πΊπ₯¬π£ γ° π | βοΈ | βοΈ | βοΈ | β |
| 0 | 0 | 1 | 1 | πΊπ£ γ° ππ₯¬β | βοΈ | β | β | β |
| 0 | 1 | 0 | 0 | ππ₯¬π£ γ° πΊ | βοΈ | βοΈ | βοΈ | β |
| 0 | 1 | 0 | 1 | ππ£ γ° πΊπ₯¬ | βοΈ | βοΈ | βοΈ | β |
| 0 | 1 | 1 | 0 | π₯¬π£ γ° πΊπβ | βοΈ | β | β | β |
| 0 | 1 | 1 | 1 | π£ γ° πΊππ₯¬β | βοΈ | β | β | β |
| 1 | 0 | 0 | 0 | πΊππ₯¬β γ° π£ | β | βοΈ | β | β |
| 1 | 0 | 0 | 1 | π₯¬π£ γ° πΊπβ | βοΈ | β | β | β |
| 1 | 0 | 1 | 0 | πΊπ₯¬ γ° π£π | βοΈ | βοΈ | βοΈ | β |
| 1 | 0 | 1 | 1 | πΊ γ° π£ππ₯¬ | βοΈ | βοΈ | βοΈ | β |
| 1 | 1 | 0 | 0 | ππ₯¬β γ° π£πΊ | β | βοΈ | β | β |
| 1 | 1 | 0 | 1 | π γ° π£πΊπ₯¬ | βοΈ | βοΈ | βοΈ | β |
| 1 | 1 | 1 | 0 | π₯¬ γ° π£πΊπ | βοΈ | βοΈ | βοΈ | β |
| 1 | 1 | 1 | 1 | γ° π£πΊππ₯¬π | βοΈ | βοΈ | βοΈ | βοΈ |
There are nice tools that support finding minimized boolean functions to generate the output signals from the input signals, e.g. http://tma.main.jp/logic/index_en.html. However, you can also do this manually! Note: Multiple minimal function forms are possible! I've picked those which I like best.
The function for output L can be written in the follwoing minimal form, where ...
- ~ means negation (NOT gate)
- fβ’g means "f logical-AND g" (AND gate)
- h+k means "h logical-OR k" (OR gate)
- just as in multiplication and addition, β’ has a stronger operator binding/ operator priority than +
L = ~F + C + G
(In text: everything is under control on the left bank in scenarios where (π£ is on the left) OR (π₯¬ is on the right) OR (π is on the right). Note that the operators are not exclusive ORs!)
The function for output R can be written in the follwoing minimal form, where ...
R = ~Fβ’~G + Fβ’G + ~Wβ’~C + Fβ’W
(In text: everything is under control on the right bank in scenarios where (the π is accompanied by the π§βπΎ independent from the side of the river) OR (π§βπΎ accompanies the π₯¬ on the left bank) OR (πΊ is accompanied by the π§βπΎ on the right side). Note that the operators are not exclusive ORs again!)
Everything is under control (output E), when the situation is under control on the left and on the right river side. The function can be written in the following form:
E = Lβ’R
The game is won (output A) when all objects are on the right river side:
A = Fβ’Wβ’Gβ’C
- No limit checking: It's only logic so far. Still, there's no limit checking mechanism that prohibits that more than two objects cross the river at the same time (which of one must be the π£).
- No sync or coupling: There's also no mechanism that automatically synchronizes a movement of the π£ with the movement of another object which is in the same πΆ.
- No history: The player must play fair and restart the game (move all objects to the left river bank) when they have lost the game and not keep on moving switches when they have actually lost.
The design uses 4 input pins for the 4 input signals:
- IN0: not connected because it is typically used for clocked designs and may be used in the future of this design
- IN1: input signal F for the position of the farmer (π§βπΎ/π£)
- IN2: input signal W for the position of the wolf (πΊ)
- IN3: input signal G for the position of the goat (π)
- IN4: input signal C for the position of the cabbage (π₯¬)
- IN5: Planned to implement an easter egg
- IN6 and IN7: not connected because not required by the current design
All four input signals can be set by using an individual sliding switch.
The design uses 7 output pins for the 4 outut signals.
Why is that? The TinyTapeout FAQ states:
Do I have to use the 7 segment? No, you can delete it and put whatever you want there. Thereβs lots of other components you can choose from the + menu. But if you get a PCB, it will only have the 7 segment on it. Youβd need to plug the board into a breadboard and add your extra components after.
So I wanted to leave the option to use the 7 segment display on the final PCB - and the Wokwi simulation.
The design uses the following output pins:
- OUT0+OUT3 (connected): output signal ~E, i.e. the top and bottom segments light up, when the game is over βββ due to an unattended situation on any river bank side
- OUT1+OUT2 (connected): output signal ~R i.e. the top-right and bottom-right segments light up, to indicate an unattended situation on the right river bank (game over β)
- OUT4+OUT5 (connected): output signal ~L i.e. the top-left and bottom-left segments light up, to indicate an unattended situation on the left river bank (game over β)
- OUT6: Planned to implement an easter egg
- OUT7: output signal A to light up the "dot LED" of the 7 segment display as an indicator that all objects have reached the right bank of the river and the game is won! πππ
There's a nice xkcd comic about the puzzle:
(Source: https://xkcd.com/1134/ - This work is licensed under a Creative Commons Attribution-NonCommercial 2.5 License.)
And there's right another one: https://xkcd.com/2348/
I am a bit late to the party. I've started to think about the design on August, 31st - and submission deadline is already one day later on September, 1st.
βοΈ Describe the design idea
βοΈ Implement the design idea using Wokwi
βοΈ Edit the Makefile and change the WOKWI_PROJECT_ID to match the project. β It's here: https://wokwi.com/projects/341614346808328788
βοΈ Enable GitHub Actions
βοΈ Describe the signal mapping to the ASIC hardware I/O pins/ Wokwi user interface in the simulation
βοΈ Hide easter egg (WIP)
βοΈ Share your GDS on twitter, tag it #tinytapeout and @matthewvenn!
βοΈ Submit it to be made
βοΈ Join the community
π² Improve the implementation to work around the current limitations.
π² Improve the implementation to work around the hardware limitations (e.g. inputs should be de-bounced as mechanical switches are used).
π² Add more output signals (e.g. indicating if game was lost because πΊ-has-eaten-π or π-has-eaten-π₯¬). (Discarded for now as the user interface is slightly limited!)