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Overview
The Morse Keyboard is based around an ATMEGA168 microcontroller. The V-USB library is
used to provide direct control of USB, eliminating the need for any other active components.
A dual 7 segment display is also attached to the IO pins. Also, the Morse key and
an additional button (to enable 'learning') is attached. There is really nothing
else to it.
A regular USB socket is used to connect directly to a host.
The display is connected directly to some IO pins (via resistors).
The morse key connects via resistors to an IO pin.
A button on board is used to start 'learning' mode. When pressed, you enter the
morse "-.-.-" and the firmware starts off with the speed you tapped this code with.
A mini speaker provides a side tone so you can hear what you're tapping. This can
be disabled in software.
Below is a somewhat hastily drawn schematic.
Parts list
Substitute values also listed where tolerance is not critical. Generally, only the
crystal and zener diodes are critical, the rest can be 10-20% out.
Qty | Description | Notes |
1 | ATMEGA168 MCU | At least -16 MHz rated |
1 | 16MHz crystal | |
2 | 22pf capacitor | XTAL loading (15p-27p ok) |
2 | 3.3v zener diode | USB clamping |
2 | 68 ohm resistor | USB limiting |
1 | 1.5k ohm resistor | USB pullup |
1 | 1uF capacitor | VCC Bypass (0.1 - 1uF ok) |
1 | 47k ohm resistor | Morsekey pulldown (22k-68k ok) |
1 | 3.3k ohm resistor | Morsekey pullup (1k - 4.7k ok) |
2 | 1k ohm resistor | Reset pullup Learn pulldown. (1k-4.7k ok) |
7 | 270 ohm resistor | LED current limiting (330k ok) |
1 | PCB mount speaker | beep beep beep |
2 | 7-segment display | Code supports common anode or common cathode. |
1 | USB B socket | |
1 | Morse key, single contact | |
1 | 2-way screw headers | To wire in morse key |
PCB
Whilst I'm no stranger to etching my own boards, I decided to go the easy route
here, and used prototype board, soldering links between components. It's easily
reproducible and still fits in the case.
Components
I elected to go small but not tiny. Most of the components are thru-hole, but a
few are SMD, especially where adjacent pads are used. Resistors are 1/8W, which
are much easier to fit on a small board than the larger 1/4w ones. And they
were super-cheap from ebay for a bag of 5000 mixed types. The display was found
from my junk box.
Case
The case is an Eclipse mint tin. Like Altoids, these come in a peoper metal
tin which lends itself well to this project. A little cutting with a mini dremel
tool allows for all the various sockets, button and display.
Morse key
A real morse key. Accept no substitutes.
I can be reached at bb @ cactii . net
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