Fercus

Wireless Symmetry Optical Keyboard

Firmware

Connect via RF 2.4GHz Proprietary, BLE 5.3, USB

Hardware

low profile optical switch

6*7 keys of each side

response time

	tr	tf	unit
pt	18	5	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.

dimension: 133 * 137 * 14.35 mm

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

              ┌────┐              
              │ pc │              
              └▲──▲┘              
               │  │               
    ┌───usb────┘  └────usb───┐    
    │                        │    
┌───▼──┬──────┐    ┌──────┬──▼───┐
│ usb1 │ usb2 │    │ usb2 │ usb1 │
├──────┴──────┤    ├──────┴──────┤
│    left     │    │    right    │
└─────────────┘    └─────────────┘

• usb2 to connect between left and right

              ┌────┐              
              │ pc │              
              └▲───┘              
               │                  
    ┌───usb────┘                  
    │                             
    │      ┌───usb────┐           
    │      │          │           
┌───▼──┬───▼──┐    ┌──▼───┬──────┐
│ usb1 │ usb2 │    │ usb2 │ usb1 │
├──────┴──────┤    ├──────┴──────┤
│    left     │    │    right    │
└─────────────┘    └─────────────┘

RF connection

              ┌────┐              
              │ pc │              
              └─▲──┘              
                │usb              
             ┌──▼───┐             
  ┌─wireless─►dongle◄─wireless─┐  
  │          └──────┘          │  
  │                            │  
┌─▼───────────┐    ┌───────────▼─┐
│     RF      │    │     RF      │
├─────────────┤    ├─────────────┤
│    left     │    │    right    │
└─────────────┘    └─────────────┘

BLE connection

              ┌────┐              
  ┌─wireless──► pc ◄──wireless─┐  
  │           └────┘           │  
  │                            │  
┌─▼───────────┐    ┌───────────▼─┐
│    BLE      │    │    BLE      │
├─────────────┤    ├─────────────┤
│    left     │    │    right    │
└─────────────┘    └─────────────┘

mix connection

              ┌────┐              
              │ pc │              
              └▲───┘              
               │                  
    ┌───usb────┘                  
    │                             
    │      ┌─wireless─┐           
    │      │          │           
┌───▼──┬───▼──┐    ┌──▼───┬──────┐
│ usb1 │  RF  │    │  RF  │ usb1 │
├──────┴──────┤    ├──────┴──────┤
│    left     │    │    right    │
└─────────────┘    └─────────────┘

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

build

compoment

• pcb 1.6mm thinkness
• plate 1.2mm thinkness
• nut m2 2.5mm height
• screw m2 4mm
• rubber 1mm thinkness
• 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

Thanks

Optical Future Discord