This Keyboard Forces You to Type Characters with Only Binary Switches
Put your ASCII knowledge to the test with a project that just has a series of eight toggle switches for inputting characters.
ASCII encoding
Shortly after commercial computers were invented, the need for a standardized way to encode characters was quickly realized, as different companies would use unique schemes that required conversion. In 1963, the American Standard Code for Information Exchange (ASCII) was released, which defined 128 different characters contained in 7 bits, and ranged from the typical English alphabet to various control characters and standard US keyboard symbols. Since its initial creation, ASCII has been extended to eight bits with an extra 128 characters for a total of 256.
Setting characters
Because extended ASCII only uses 8 bits, Hackaday.io user HIGEDARUMA had the idea to arrange a panel of eight toggle switches that would allow him to set each individual bit. By default, the switch is in the "down" position, or 0, whereas flipping it upwards changes it into a 1. Pressing the momentary pushbutton switch just to the right of this bank tells the attached microcontroller to read the switch states, convert the values into a single value, and send the resulting character over USB to the attached host device.
Storing keys
While outputting a single character is fine for some applications, many other functions rely on a combination of key presses. Therefore, HIGEDARUMA's 8-bit Keyboard also has a key storage feature that can hold up to three characters in memory. For example, the classic Ctrl + Alt + Delete shortcut can be accessed by entering the prior characters into the switch panel while pressing the store button between each one, while hitting send transmits all three simultaneously.
Extra functionality
One last feature of the 8-bit Keyboard is the addition of a physical lock, which can be turned to activate the locking key function. Due to how ASCII encodes characters, a lowercase a has a different code than an uppercase A, which means that switching between the two is quite a hassle. To address this, the lock can store a single modifier key while the user enters their character of choice into the bank of toggle switches. If the shift key is locked, entering a lowercase letter will convert it to uppercase automatically.
To see more about this fun project, you can read HIGEDARUMA's write-up here on Hackaday.io or watch this YouTube video where he demonstrates how it works.