#+TITLE: Fercus Wireless Symmetry Optical Keyboard[[./doc/image/overview.jpg]]

• Firmware ** Connect via RF 2.4GHz Proprietary, BLE 5.3, USB ** COMMENT optical switch with diff trigger mode

- schmitt trigger

- adc trigger

- adc difference

** COMMENT function

- multiple layers

- repeat mode

• Hardware ** Switch 6*7 keys of each side, low profile optical switch

- raesha low profile optical switch

- keychron low profile optical switch

- razer low profile optical switch

** Spec Dimension: 133 * 137 * 14.35 mm

Weight of each side: 159 ± 1 g

power input: DC 5V 500mA

current: 40 mA * 7 * 15 / 1000 = 4.2 mA

** response time | | tr | tf | unit | | pt | 18 | 5 | us |

| sw | 200-2000 | 200-2000 | us |

The speed of optical switch depends on the speed of finger, the shortest time for finger to press a switch is about 200 us, but usually it takes a few milliseconds. Test on mcu's adc at f_adc = 12MHz, f_s = 12 / 14 MHz, resolution = 12 bits. Get the average of the five.

** COMMENT test | | min | typ | max | unit | cond | | pt | 0.2 | | 0.3 | V | ir 20mA, without switch |

• Manual ** fn key fn1: switch layout

fn2: switch connection mode. long press: rf Unbind with dongle

fn3: battery status

fn4: power on led green. power off led red.

** usb connection

• usb1 to connect with pc #+begin_src org ┌────┐
  │ pc │
  └▲──▲┘
  │ │
  ┌───usb────┘ └────usb───┐
  │ │
  ┌───▼──┬──────┐ ┌──────┬──▼───┐ │ usb1 │ usb2 │ │ usb2 │ usb1 │ ├──────┴──────┤ ├──────┴──────┤ │ left │ │ right │ └─────────────┘ └─────────────┘ #+end_src
• usb2 to connect between left and right #+begin_src org ┌────┐ ┌────┐
  │ pc │ │ pc │
  └▲───┘ └───▲┘
  │ │
  ┌───usb────┘ └────usb───┐
  │ │
  │ ┌───usb────┐ ┌───usb────┐ │
  │ │ │ │ │ │
  ┌───▼──┬───▼──┐ ┌──▼───┬──────┐ ┌──────┬───▼──┐ ┌──▼───┬──▼───┐ │ usb1 │ usb2 │ │ usb2 │ usb1 │ │ usb1 │ usb2 │ │ usb2 │ usb1 │ ├──────┴──────┤ ├──────┴──────┤ ├──────┴──────┤ ├──────┴──────┤ │ left │ │ right │ │ left │ │ right │ └─────────────┘ └─────────────┘ └─────────────┘ └─────────────┘ #+end_src

┌────┐

│ pc │

└▲──▲┘

│ │

┌───usb────┘ └────usb───┐

│ │

│ ┌───usb────┐ │

│ │ │ │

┌───▼──┬───▼──┐ ┌──▼───┬──▼───┐

│ usb1 │ usb2 │ │ usb2 │ usb1 │

├──────┴──────┤ ├──────┴──────┤

│ left │ │ right │

└─────────────┘ └─────────────┘

** RF connection #+begin_src org ┌────┐
│ pc │
└─▲──┘
│usb
┌──▼───┐
┌─wireless─►dongle◄─wireless─┐
│ └──────┘ │
│ │
┌─▼───────────┐ ┌───────────▼─┐ │ RF │ │ RF │ ├─────────────┤ ├─────────────┤ │ left │ │ right │ └─────────────┘ └─────────────┘ #+end_src

** BLE connection #+begin_src org ┌────┐
┌─wireless──► pc ◄──wireless─┐
│ └────┘ │
│ │
┌─▼───────────┐ ┌───────────▼─┐ │ BLE │ │ BLE │ ├─────────────┤ ├─────────────┤ │ left │ │ right │ └─────────────┘ └─────────────┘ #+end_src

** mix connection #+begin_src org ┌────┐
│ pc │
└▲───┘
│
┌───usb────┘
│
│ ┌─wireless─┐
│ │ │
┌───▼──┬───▼──┐ ┌──▼───┬──────┐ │ usb1 │ RF │ │ RF │ usb1 │ ├──────┴──────┤ ├──────┴──────┤ │ left │ │ right │ └─────────────┘ └─────────────┘ #+end_src

** power auto power on/off when usb cable connected/disconnected

when idle for a week, first use fn4 to power off in firmware, then turn off hardware power switch

** layout

• qwerty[[./doc/keyboard-layout-editor/qwerty.png]]

• Assembly ** compoment

• pcb 1.6mm thickness
• plate 1.2mm thickness
• nut m2 length 2.5mm, od 3mm
• screw m2 length 4mm
• rubber 1mm thickness
• li-on battery 101550 800mAh, molex picoblade 3 pin, 8 cm cable length
• usb-c to usb-c cable 1 m
• usb-c to usb-a cable 2 m

** COMMENT PCBA soldering nut on pcb, or soldering nut on plate

** Overall

1. Install switches on the plate, the LED position of the switch is facing upwards.
2. Install the plate to the PCB.[[./doc/image/assembly/assembly-1.jpg]]
3. Install the screws.[[./doc/image/assembly/assembly-2.jpg]]
4. Install keycaps.

• Thanks [[https://discord.com/channels/715975244896272618][Optical Future Discord]]

• COMMENT FAQ ** COMMENT keys layout *** thumb finger splay increase the x axis distence between rows more thumb keys may be hard to press *** middle finger [[./doc/keyboard-layout-editor/middle-finger.png]] mid finger at wsad postion, non stagger is better to press up bad for playing fps game

same for pinky stagger 8 mm instand of 12 mm