# Dev notes — 2023-08-07

## Keypad

An actual hexadecimal layout:

```
0 1 2 3
4 5 6 7
8 9 A B
C D E F
```

Another:

```
1 2 3 A
4 5 6 B
7 8 9 C
0 F E D
```

The conventional layout for cheap hardware:

```
1 2 3 A
4 5 6 B
7 8 9 C
* 0 # D
```

Kim-1:

```
    GO  ST  RS
AD  DA  PC  +
C   D   E   F
8   9   A   B
4   5   6   7
0   1   2   3
```

COSMAC VIP/CHIP-8:

```
1 2 3 C
4 5 6 D
7 8 9 E
A 0 B F
```

CHIP-8 to QWERTY mapping:

```
1 2 3 4
Q W E R
A S D F
Z X C V
```

## Turtle graphics

- yesterday Elizabeth had the great idea to create a turtle robot to go with the paper computer
- a minimal LOGO would be a fantastic (if challenging) program to write for the computer
  - it could use the hex keypad:
    - using CHIP-8 layout...
    - A key: mode toggle
    - mode 1: numeric
    - mode 2: commands (tokens?)... something like this:
      - `F` - mode toggle
      - `2` - forward
      - `4` - left
      - `6` - right
      - `0` - reverse
      - `5` - turn
      - `1` - pen up
      - `C` - pen down

## Dot-matrix display

- Maybe try 5x5, like the micro:bit?