• Portable Linux computer / cyberdeck prototype.
• User-facing compute, networking, radio, display, keyboard, audio, and battery operation.
• Current stage: requirements capture and architecture selection; schematic capture should not begin until the compute module, screen/keyboard interface, and battery architecture are confirmed.

• Boot and run Linux on Raspberry Pi Compute Module 5.
• Use selected CM5 SKU SC1598 / CM5108000: 8 GB RAM, Lite / 0 GB eMMC, wireless.
• Support LTE Cat-4 cellular data and GNSS using a SIM7600G-H-M.2 module.
• Support LoRa using an RP2040-LoRa development board with SX1262.
• Provide one USB-C port for power and data.
• Provide one USB-A 3.0 host port.
• Provide one HDMI port.
• Connect to the specified screen/keyboard assembly.
• Drive a small speaker.
• Operate from a battery connection and support charging/power-path behavior.

Diagram

• Selected direction: Raspberry Pi Compute Module 5 carrier board.
• CM5 variants support 2 GB, 4 GB, 8 GB, and 16 GB LPDDR4x; use 8 GB minimum.
• Selected CM5 is Lite / 0 GB eMMC, so the carrier will provide a microSD card slot for boot/storage.
• Selected CM5 is wireless-capable, so enclosure antenna clearance or external antenna strategy must be handled.
• CM5 main input is 5 V and the carrier power system must support CM5 peak current plus display, USB, LTE, speaker, and battery charging loads.

• Target module: SIM7600G-H-M.2 / SIM7600X-H-M2 family.
• Supply range found: 3.3–4.2 V.
• Power rail must support approximately 2 A-class transmit bursts with large low-ESR bulk capacitance near the module.
• Host interface is USB 2.0; route as 90 ohm differential pair.
• Needs SIM/eSIM decision, cellular antenna, diversity antenna decision, GNSS antenna decision, RF keepouts, and regulatory review.

• Target board appears to be Waveshare RP2040-LoRa with SX1262.
• Board size found: 21 mm x 41 mm.
• Frequency options:
  • LF: 410–525 MHz.
  • HF: 850–930 MHz.
• Antenna connector: onboard IPEX with included IPEX-to-SMA adapter cable.
• Interface to Linux host should be decided: USB, UART, or a carrier-level debug/programming path.

• Candidate: Waveshare 6.25inch DSI LCD (B), 720 x 1560 IPS capacitive touch display.
• Interface: Raspberry Pi-style 2-lane MIPI DSI plus I2C touch.
• Power: 5 V panel power plus 3.3 V/I2C side signals per Waveshare pinout.
• Advantage: documented for Raspberry Pi DSI overlays, making CM5 a better match than an arbitrary RK3588 SOM.
• Verify exact CM5 DSI connector mapping/cable orientation before schematic capture.

• Reference: M5Stack Unit CardKB / CardKB v1.1.
• Reference interface: I2C at address 0x5F over HY2.0-4P/Grove-style connector with GND, 5 V, SDA, SCL.
• Reference size: approximately 84–88 mm x 54 mm x 5 mm depending revision.
• User direction: design a custom keyboard PCB slightly longer than CardKB.
• Recommended implementation: direct-wired keyboard matrix on the main board, scanned by a small onboard keyboard MCU, exposed to CM5 as USB HID with optional wake/power sideband GPIO.

• USB-C role is currently ambiguous and must be defined before schematic capture.
• USB-A 3.0 requires a compute platform with USB 3.x host capability and controlled-impedance routing.
• Internal peripherals may exceed available host ports; likely need a USB 2.0 hub for LTE, keyboard/touch, LoRa, and debug if these are USB.

• External HDMI is feasible but requires 100 ohm differential routing, ESD protection, DDC, hot-plug detect, connector shield strategy, and 5 V HDMI power.
• If the internal screen also needs HDMI, the compute platform must support multiple display outputs or the design must choose between internal display and external HDMI.

• Small speaker path should use a dedicated class-D amplifier.
• Interface depends on compute platform: I2S preferred if exposed; USB audio is fallback.
• Speaker impedance and power target are needed.

• Battery direction: compact communicator/tablet-style Li-ion/LiPo pouch pack.
• Recommended chemistry is now 1S Li-ion/LiPo for thin mechanical packaging, with high-current boost conversion to the 5 V system rail.
• Confirmed battery pack: 1S2P using 2x BatterySpace PL-5467100-2C cells with Tenergy 32190 PCM, 8500 mAh / ~31.5 Wh nominal.
• Use USB-C PD charging with a 1S switching charger/power-path, I2C fuel gauge, NTC monitoring, and run-while-charging support.
• Include fuel gauge, pack protection, power button/soft-shutdown, and low-battery cutoff.

• If using SOM/SBC: custom carrier board likely 6 layers minimum due USB 3.0, HDMI, LTE USB, RF, and power integrity.
• If raw RK3588S2 + LPDDR4x is chosen: expect 8+ layer HDI/microvia design, controlled impedance, DDR simulation/validation, and substantially higher cost/risk.
• RF antennas and M.2 connector placement must be considered with the enclosure, display metalwork, and battery location.

• Linux BSP support depends on selected RK3588S2/SOM/SBC vendor.
• Need serial console/debug access.
• LTE should be exposed to Linux as USB modem interface; support ModemManager/NetworkManager where possible.
• RP2040-LoRa requires firmware update/programming path.
• Keyboard/display drivers depend on the actual interface of the screen/keyboard assembly.

• Keyboard assembly likely dominates product size; candidate AKP846 dimensions found around 371 x 219 x 21 mm.
• Need exact enclosure size, mounting hole locations, connector exits, battery location, antenna locations, speaker port, cooling path, and SIM access.
• RK3588-class SoC needs heat spreader or conduction path.

1. Use SOM/SBC for compute rather than raw RK3588S2 + LPDDR4x for the first prototype.
2. Treat SIM7600G-H-M.2 as a high-burst-current RF module requiring a dedicated 3.8 V-class supply and RF-aware layout.
3. Treat the RP2040-LoRa board as a daughterboard unless the user wants to integrate the LoRa circuit directly.
4. Do not design display/keyboard connector circuitry until the exact interface is documented.
5. Use at least a 6-layer carrier PCB for the high-speed/RF carrier approach.

• Prototype-first design, not immediate production certification.
• Linux runs on a purchased RK3588S2/RK3588-class module/SBC.
• Cellular modem is USB-connected.
• LoRa board can be connected as a daughterboard.
• Screen/keyboard assembly is used as a purchased module rather than reverse-engineered internally.
• Battery is rechargeable Li-ion/LiPo with charging from USB-C.

1. Keyboard final layout drawing: 60-key legend, Fn map, tact/keycap part selection.
2. Enclosure CAD kickoff: hinge, SMA bulkhead locations, antenna keepouts, service hatch.
3. RJ45 Ethernet is omitted.
4. Should the custom keyboard enumerate as USB HID, I2C, or both?
5. What keyboard switch/key technology and approximate size should be used?
6. USB-C role is confirmed as PD sink/UFP charge plus USB 2.0 data, not USB 3.0 and not full dual-role/source.
7. Is HDMI for external output only, or should the internal DSI display and external HDMI work simultaneously?
8. Which LoRa frequency band is required: 433/470, 868, or 915 MHz?
9. Do you want internal antennas or external SMA connectors for LTE/GNSS/LoRa?
10. What speaker impedance/power target and enclosure size/shape should be used?

• Initial specification created from user requirements.
• Project renamed to Linux Cyberdeck.
• Architecture risk review added: raw RK3588S2 + LPDDR4x is not recommended for the first prototype.
• Updated per user direction: switched from RK3588-class SOM carrier to Raspberry Pi Compute Module 5 carrier using attached CM5 datasheet, retaining tablet-style battery, M5Stack CardKB as keyboard size/interface reference, custom keyboard PCB, and Waveshare 6.25inch DSI LCD (B) display candidate.
• Updated per user direction: selected DigiKey SC1598 / CM5108000 CM5 Lite wireless 8 GB module, USB-C charging+data, microSD instead of NVMe, and direct-wired custom keyboard via onboard keyboard MCU.
• Updated per confirmed decisions attachment: USB-C data is USB 2.0 gadget/rpiboot, battery is 1S2P 8500 mAh verified pack, keyboard is split RP2040/QMK PCB, and only keyboard layout plus enclosure CAD kickoff remain open.