Should anyone care to convert without rebraining, it is not that complicated.
The DIN-8 pinout is as follows:
- 1, 8 Clock
- 2 Data
- 3 Reset
- 4 Ground
- 5 +5V
- 6 Busy
- 7 End
The protocol has eight bit key codes. A clock pulse signals each bit. Additionally, if the end signal is high, that is the last bit of the key code, ready for the computer to receive. While the computer is busy, it can optionally inhibit the keyboard sending by pulling busy low.
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The eighth (high) bit indicates key release versus press.
Code: Select all
+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+-------+
|F1 |F2 | | ` | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 0 | - | = | \ |BS | |ESC|NUM|SCL LCK|
+-------+ +-----------------------------------------------------------+ +---------------+
|F3 |F3 | | TAB | Q | W | E | R | T | Y | U | I | O | P | [ | ] | | | 7 | 8 | 9 | * |
+-------+ +-----------------------------------------------------| | +---------------+
|F5 |F6 | | CTRL | A | S | D | F | G | H | J | K | L | ; | ' | ENTER | | 4 | 5 | 6 | - |
+-------+ +-----------------------------------------------------------+ +---------------+
|F7 |F8 | | SHIFT | Z | X | C | V | B | N | M | , | . | / | SHIFT | | 1 | 2 | 3 | |
+-------+ +-----------------------------------------------------------+ +-----------| + |
|F9 |F10| | ALT | | SPACE | |CAPS | | 0 | . | |
+---+---+ +-----+ +--------------------------------------+ +-----+ +-------+---+---+
+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+-------+
|3B |3C | |29 |02 |03 |04 |05 |06 |07 |08 |09 |0A |0B |0C |0D |2B |0E | |01 |45 |46 |
+-------+ +-----------------------------------------------------------+ +---------------+
|3D |3E | |0F |10 |11 |12 |13 |14 |15 |16 |17 |18 |19 |1A |1B |1C | |47 |48 |49 |37 |
+-------+ +-----------------------------------------------------| | +---------------+
|3F |40 | |1D |1E |1F |20 |21 |22 |23 |24 |25 |26 |27 |28 | | |4B |4C |4D |4A |
+-------+ +-----------------------------------------------------------+ +---------------+
|41 |42 | |2A |2C |2D |2E |2F |30 |31 |32 |33 |34 |35 |36 | |4F |50 |51 |4E |
+-------+ +-----------------------------------------------------------+ +-----------| |
|43 |44 | |38 | |39 | |3A | |52 |53 | |
+---+---+ +-----+ +--------------------------------------+ +-----+ +-------+---+---+
The from-keyboard signals are open collector, coming from a 7407 buffer. So enable pull-up on the MCU inputs. Furthermore, it's fine to connect directly to a 3.3V pin.
The to-keyboard signals go to a MC14049UB inverting buffer. And there are pull-ups inside the keyboard, that is, to 5V. So one really ought to use a level shifter if driving from a lower voltage MCU. The standard Philips i2c one (bidirectional, open collector) kinda works, but a unidirectional one using a complementary buffer like a 74AHCT125 is simpler.
