Linux Cyberdeck Design

flux

There’s still a moderate amount left before this is a full manufacturable board. The first-pass schematic is started, but we are not ready for PCB layout/manufacturing yet.
Main things still left to figure out
  1. Display connection
    • Exact Waveshare 6.25" DSI LCD-B connector pinout
    • DSI lane count
    • Backlight power/current
    • Touch interface, if any
    • Correct FPC connector part
  2. Battery and power
    • Exact 10,000 mAh battery pack
    • Battery connector/current rating
    • Battery protection/NTC details
    • Confirm charger settings for that pack
    • Validate 5 V boost converter can handle CM5 + LTE + display + USB-A peaks
  3. Protection parts
    • USB-C ESD protection
    • USB-A USB 3.0 ESD protection
    • HDMI ESD protection
    • SIM card ESD protection
    • Possibly battery/input fuse or protection
  4. Regulator final values
    • Final inductor part numbers
    • Capacitor voltage/package choices
    • TPS61288 compensation check
    • Thermal/current margin check
    • Layout-sensitive switching-node constraints
  5. CM5 details
    • Decide whether to add RTC backup for CM5 VBAT
    • Decide whether to expose nRPIBOOT/service pads
    • Confirm GPIO assignments for LTE, audio, IMU, keyboard wake
  6. LTE/SIM7600 details
    • Confirm exact SIM7600G-H-M.2 hardware guide handling for VDD_AUX and VDD_1V8
    • Confirm LTE/GNSS antenna connector placement strategy
    • Add SIM ESD
    • Add RF/layout keepout rules
  7. Keyboard board
    • Main-board FPC is planned, but keyboard PCB itself still needs to be designed
    • Need switch/keycap sourcing
    • Need keyboard RP2040 schematic/firmware pin map finalized
  8. Mechanical basics
    • Rough board size
    • Port locations
    • Battery location
    • Screen/keyboard placement constraints
    • Mounting holes
    • Antenna placement/keepouts
  9. PCB layout setup
    • Stackup choice, likely 6-layer because of USB 3.0, HDMI, MIPI DSI, RF, and power density
    • Controlled-impedance rules
    • Differential-pair rules
    • Power trace/current rules
    • Thermal copper areas
  10. Bring-up and manufacturing prep
  • Test pads
  • Debug headers
  • Board bring-up checklist
  • BOM cleanup
  • Footprint review
  • DRC
  • Gerbers/BOM/pick-and-place
My estimate
Schematic is roughly 55–65% figured out.
Full board readiness is more like 30–40% complete, because layout, power validation, protection, display details, and mechanical constraints are still significant.
The biggest blockers are:
  1. Exact display connector/pinout
  2. Exact battery pack
  3. Power validation for the 5 V rail
  4. ESD/protection parts
  5. Mechanical board size/port placement
  6. Keyboard PCB design
Once those are decided, the remaining work becomes much more straightforward.
Power, display, protection
Find display pinout
Validate power rail
Add protection parts
Add test pads
Review battery connector

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Keyboard and Display Direction — Linux Cyberdeck
Status
Draft direction based on the user's latest requirements and researched module documentation.
User Direction
  • Use an RK3588-class SOM carrier rather than a raw RK3588S2 + discrete LPDDR4x board.
  • Battery should be a large tablet-style battery pack sized for useful runtime and enough peak power for the device.
  • Replace the previous AliExpress smart-keyboard uncertainty with:
    • Keyboard reference: M5Stack Unit CardKB / CardKB v1.1.
    • Screen alternative: Waveshare 6.25inch DSI LCD (B).
  • Consider designing a custom keyboard PCB that is slightly longer than the M5Stack CardKB.
M5Stack CardKB Reference Findings
Sources checked:
Design-relevant facts:

Table

ItemFinding
InterfaceI2C
I2C address0x5F
ConnectorHY2.0-4P / Grove-style connector
Connector pinoutGND, 5V, SDA, SCL
Supply5 V
CurrentApprox. 20 mA found in PDF resource; not consistently listed on product page
ControllerCardKB v1.1 page lists ATMega8A; PDF resource also references ATmega328P / MEGA328P-AU, so exact revision matters
Key countProduct page says 50 keys; PDF resource says 56 keys, likely revision/document mismatch
SizeProduct page: 88.0 x 54.0 x 5.0 mm; PDF resource: 84 x 54 x 5 mm
WeightAbout 14–17 g depending source/revision
Custom Keyboard PCB Direction
Recommended direction: build a custom keyboard PCB inspired by CardKB but not constrained to cloning it exactly.
Proposed Electrical Architecture
Diagram



  
    
  
  
    
  













Key Matrix
Keyboard MCU
I2C to SOM / EC
Optional USB HID to SOM
Status LEDs / Backlight Optional
RK3588 SOM Carrier
  • USB HID keyboard is the lowest-friction Linux interface if the keyboard connects directly to the RK3588 SOM.
  • I2C keyboard is useful if the design includes an embedded controller / power-management MCU that scans keys and wakes the system.
  • Best carrier-board architecture may include both:
    • Keyboard MCU enumerates as USB HID for Linux input.
    • A few wake/power keys also connect to an always-on controller or SOM wake GPIO.
Mechanical Direction
  • Baseline CardKB reference size: roughly 84–88 mm long x 54 mm wide x 5 mm thick.
  • User wants custom keyboard PCB slightly longer than CardKB.
  • Proposed first mechanical target: 100–110 mm long x 54–60 mm wide, pending desired key spacing and enclosure width.
  • Use real switch/keycap geometry before PCB layout. If using tactile domes, Kailh Choc, Blackberry-style keys, or small SMD tact switches, the key pitch and board thickness change significantly.
Waveshare 6.25inch DSI LCD (B) Findings
Sources checked:
Design-relevant facts:

Table

ItemFinding
ProductWaveshare 6.25inch DSI LCD (B), SKU 35000
Resolution720 x 1560
PanelIPS, optical bonding, toughened glass
Brightness500 cd/m²
Touch5-point capacitive touch
Touch interfaceI2C; Goodix touchscreen appears as 10-0014 Goodix Capacitive TouchScreen
Display interfaceRaspberry Pi-style MIPI DSI
RefreshUp to 60 Hz through Raspberry Pi DSI
Power5 V via pogo/spring pins or PH2.0 4-pin cable depending host board
DSI connector15-pin interface definition on panel side; uses 22-pin DSI cable for Pi 5/CM5/CM4/CM3 and 15-pin FPC for Pi 4/3-style boards
DSI lanesPinout shows two data lanes plus clock: DN0/DP0, DN1/DP1, CN/CP
Interface pinout1 GND, 2 DSI1_DN1, 3 DSI1_DP1, 4 GND, 5 DSI1_CN, 6 DSI1_CP, 7 GND, 8 DSI1_DN0, 9 DSI1_DP0, 10 GND, 11 SCL0, 12 SDA0, 13 GND, 14 3V3, 15 3V3
Included cablesDSI-Cable-12cm, 15-pin 1.0 mm FPC cables, PH2.0 4-pin cable
SoftwareRaspberry Pi overlay vc4-kms-dsi-waveshare-panel,6_25_inch; RK3588 support will require SOM vendor device-tree/display-driver compatibility work
Display Integration Risk
The display is documented for Raspberry Pi DSI, not guaranteed plug-and-play on every RK3588 SOM. The SOM must expose a compatible 2-lane MIPI DSI output, I2C for touch, 3.3 V control, 5 V panel power, and Linux device-tree support for the panel/touch controller.
Revised Carrier Architecture Impact
  • Select an RK3588-class SOM with documented MIPI DSI output and Linux DTS examples.
  • Add a panel FPC connector or adapter footprint compatible with the Waveshare cable/pinout.
  • Provide 5 V panel power with enough margin and switch/control if needed.
  • Route DSI as controlled-impedance high-speed differential pairs with tight skew control and solid ground reference.
  • Route I2C touch lines with correct voltage domain and pull-ups.
  • Design the keyboard as a separate low-speed PCB/daughterboard or integrated lower section of the carrier, depending enclosure shape.
Open Questions Before Schematic Capture
  1. Should the keyboard be USB HID, I2C, or both?
  2. What key technology should the custom keyboard use: small tactile switches, low-profile mechanical switches, Blackberry-style keypad, or rubber-dome style?
  3. Desired keyboard dimensions: is 100–110 mm long acceptable, or should it be closer to the original CardKB?
  4. Should the keyboard be a separate replaceable daughterboard or part of the main carrier PCB?
  5. Which exact RK3588 SOM will be used, and does it expose MIPI DSI lanes compatible with the Waveshare screen?
  6. Should the 6.25inch display be portrait, landscape, or physically rotated with software rotation?
  7. What tablet-battery voltage/chemistry should be used: 1S, 2S, or a smart battery pack?

  • Status

  • User Direction

  • M5Stack CardKB Reference Findings

  • Custom Keyboard PCB Direction

  • Proposed Electrical Architecture

  • Recommended Interface Choice

  • Mechanical Direction

  • Waveshare 6.25inch DSI LCD (B) Findings

  • Display Integration Risk

  • Revised Carrier Architecture Impact

  • Open Questions Before Schematic Capture