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unified_retro_keyboard
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Update README.md

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@ -13,6 +13,14 @@ even slightly simplify the hardware layer of the firmware.
<img alt="Assembly Rendering" src="images/PCB-assembly-rendering.jpg" height=75% width=75%>
## Features
- Parallel or serial output
- Up to 8 configuration settings via an up-to-8 position DIP switch
- Apple 1 and Apple 2 compatible outputs. Other configurations can be supported by
making a custom cable.
- Can decode arbitrary keyboards up 16 rows by 8 columns by making a custom keyboard cable.
- Supports up to 3 keyboard LEDs
- Supports up to 3 "special" host outputs, such as RESET, SCREEN_CLEAR, BREAK, etc.
## Overview
- The keyboard rows are driven by a pair of 74LS138 decoders, allowing 4 GPIO
@ -24,6 +32,7 @@ even slightly simplify the hardware layer of the firmware.
- One GPIO line is used to control a keyboard LED.
- Three of the ISP lines are also used as outputs to controll two more Keyboard
LEDs and one more "special" output line.
- The DIP switch is wired into row 15 (last row) of the matrix.
- The top two parallel I/O bits can also be configured as UART I/O. This could
be used to provide serial output instead or parallel output, to support a
bootloader, or even to accept a serial input stream from another computer to