Sometimes you don't need many keys for a project, and the Arduino Beetle has 10 I/O pins plus a USB port for small projects. This combination is ideal for:
* USB based keyboards (or mice)
* Handwired (although PCB options are possible too)
* One to 10 keys are trivial
* Up to 25 keys are not much harder, though a PCB would help.
* Pogramable with macros, layers, supported by TODO: {TMK | QMK | Easy AVR} software
* Numeric pads (often 17, 19, 21, or 22 keys)
* Converting key "switch testers" to macro pads.
* Simple, inexpensive hardware
My first project based on this technology is a foot-operated set of 4 (or 8) switches. The plan is to support four modifier keys, to be foot-operated. They are: Command (or Windows), Option, Control, and Shift.
The thought is that these could be used to support users with some hand problems.
This project will not require the manufacture of any printed circuit boards, and the switches will be hand-wired to the Beetle.
Parts count, and expenses are low.
Because the Beetle has 10 I/O pins available, and I only need 4 (or 8), I'll (hand) wire then directly.
Again, with 10 I/O pins it is possible to do a standard keyboard scanning matrix of 5 x 5 (up to 25 keys), or 4 x 6 (up to 24 keys, with a scan layout that more closely matches the physical). These matrixes will require a diode at each switch to prevent "ghosting."
For example, searching Amazon for: numeric pad USB, most numeric pads have 17, to 22 keys on them, so the little Beetle will be quite capable for this application.
| Parts for 4 switches | Qty | Jameco | URL |
|---|---|---|---|
| Adafruit Beetle | 1 | $9.95 | 2213325 |
| 5 Black RCA jacks | 2 | $1.95 | 229921 |
| 4 RCA sockets (1x3") | 2 | $0.49 | 319429 |
| Case | 1 | $4.95 | 675462 |
| USB-A to USB-micro B | 1 | $1.95 | 2196086 |
| Foot switches (4) | 4 | $14.00 | (Tatoo, drom China) |
| ---------------- | --- | -------- | |
| Estimated total | $33.29 |
- Beetle $7.90 Digikey. USB + 10 I/O; 20mm x 22mm
- 3.5 mm socket (need 4+) $0.74ea Digikey
- 3.5mm jack (need 4+) $0.84ea Digikey
- Case 3.6 x 2.25 x 1". Serpac 111i project box. Install RCA sockets in top. digikey $4.50
- (for expanded experiments) 5v, 8 bit shift reg. $0.43 Digikey
| Parameter | Value |
|---|---|
| Microcontroller | ATmega32u4 |
| Clock Speed | 16 MHz |
| Operating Voltage | 5V DC |
| Digital I/O Pins | 10 |
| PWM Channels | 4 |
| Analog Input Channels | 5 |
| UART | 1 |
| I2C | 1 |
| Micro USB | 1 |
| Power Ports | 2 |
| Flash Memory | 32 KB (4KB used by bootloader) |
| SRAM | 2.5 KB |
| EEPROM | 1 KB |
| Size | 20x22x3.8mm |
- Mini-Emoticon-Keyboard using the similar Adafruit Trinket.
- The keytee project. GitHub project. Project files. Same processor, custom PCB.
- Clueboard Switch Tester Kit, or Assembled
- NovelKeys switch tester
Beetle Digital PWM Analog
Silkscreen Pin Channel Channel UART I2C
RX 0 Serial-RX
TX 1 Serial-TX
SDA 2 SDA
SCL 3 3 SCL
9 9 9 A9
10 10 10 A10
11 11 11
A0 A0 A0
A1 A1 A1
A2 A2 A2
Power:
Beetle
Silkscreen Description
+ VCC
- GND
Development resources:
- Plug-it in
- Blue LED on the Beetle should flash
- macOS:
- Apple menu, About this Mac
- Click System Report...
- Select USB from the left column
- Look for Arduine Leonardo in the USB tree
- Windows:
- TODO:
- aa
Development order for Beetle experiments (Arduino-only code) √ reset keyboard/controller after completing task √ 4-function calculator operations in floating point timing 1.5 million times. Time millis and report. Use random numbers?
- Repeat timing with BigNumbers
- Create a calculator that takes character array (string) input, treats each as a keystroke. Repeat 100,000 times. Report elapse time & result.
- example: 123+222=345
- 1/991000/0.5+800.765=2800.76499999998
- Maybe use PString for display: http://arduiniana.org/libraries/PString/
- Repeat calcs and timing with "BigNumber" -- https://github.com/nickgammon/BigNumber
- Mac OS X calculator seems to display and retain up to 19 digits
- Arduino LCD display is 2 x 16 characters. (We could use more and have "guard digits") some 4x20 displays too
- Sun serial (1200 baud, start, stop, inverted) by Ben Rockwood
- https://github.com/benr/SunType5_ArduinoAdapter_SoftwareSerial
- sunSerial(10, 11, true); // rxpin txpin, reverse logic (yes); connect to serial pads under Beetle
- Light LED on every correctly received serial character. Blink twice if error
- Connect to G80-9009 via breadboard (no DIN needed)
- Look to see if any charactrs come through a) for main Kbd; b) for ancillary keys.
- Install Sun scan code table, and output to USB for verification.
- Pull request for Ben Rockwood's Sun to USB adapter. (docs)
- Increase 6KRO to many, many KRO with buffer
- Sun keyboard scan code resources
Using usb keyboard: https://www.pjrc.com/teensy/td_keyboard.html Google: arduino sending scan codes to usb keyboard
2-wire Arduino to LCD project: http://www.instructables.com/id/2-Wire-LCD-interface-for-Arduino-or-Attiny/
and again (2011): http://3g1l.com/blog-cheap-arduino-2-wire-lcd-display-0
and again (2012): https://scargill.wordpress.com/tag/2-wire-lcd-for-arduino-a-working-example/
and again: https://playground.arduino.cc/Code/LCD3wires
or "just buy it" ebay search: arduino 2 wire lcd. 4 x 20 = less than $10
Module dimension: 99mm x 60mm x 12mm.
Viewing area size: 64.5mm x 16mm
Sun kbd to USB via Beetle:
Load code, test, point Sun-only codes for F13-F24 or so. Test.
keyboard.println() is broken. Space instead of \n.
scan codes instear od keyboard.print
Buffered USB for > 6 KRO