Raspberry Pi Compute Module 4 (CM4)
RF Monitoring Cyberdeck
Overview
A compact clamshell cyberdeck designed for RF monitoring and programming featuring complete air-gapped isolation and physical kill switches.
Kieron StainsbySystem architecture
POWER
MCU
RF
ACTUATOR
DISPLAY
- POWER_MANAGEMENT → COMPUTE_COREPowerMain regulated system power to compute module
- COMPUTE_CORE → RF_SDR_FRONTENDUSBInternal USB 2.0 bus routed through hardware kill switch domain
- COMPUTE_CORE → SUB_GHZ_RADIOSPISPI bus interface for Sub-GHz packet transceiver control
- KEYBOARD_MCU → COMPUTE_COREUSBInternal USB HID keyboard connection to main host SBC
- KILL_SWITCH_DOMAIN → RF_SDR_FRONTENDPowerPhysical interruption of power rail and antenna shorting for air-gap isolation
- COMPUTE_CORE → DISPLAY_PANELUSBDisplay output and touch controller interface
Bill of materials
| Part number | Type | Component | Manufacturer | Package | Qty | Datasheet | Match |
|---|---|---|---|---|---|---|---|
| BQ25713RSNT | POWER | Texas Instruments BQ25713 + TI TPS65987D USB-PD Manages 4S rechargeable battery pack, charging, and 5V/3.3V power tree generation for 4-8 hour runtime | Texas Instruments | 32-WFQFN Exposed Pad | 1 | Matched | |
4 alternatives consideredAI verified | |||||||
| CM4 | MCU | Raspberry Pi Compute Module 4 (CM4) Acts as the central host running the primary OS, UI, and SDR processing pipeline | Gardner Bender | — | 1 | Matched | |
| RTL2832U | RF | Realtek RTL2832U + R820T2 Provides wideband RF monitoring and spectrum capture from 24MHz to 1.7GHz+ | REALTEK | — | 1 | Matched | |
1 alternatives consideredAI verified | |||||||
| SX1262DVK1CAS | RF | Semtech SX1262 Handles ISM band packet capture, LoRa monitoring, and local RF injection tasks | Semtech | Box | 1 | Matched | |
1 alternatives consideredAI verified | |||||||
| RP2040 | MCU | Raspberry Pi RP2040 Drives the custom split-matrix mechanical keyboard and processes shortcuts via QMK/VIA | Raspberry Pi | QFN-56 | 1 | Matched | |
| SKY13358-378LF | ACTUATOR | DPDT Toggle Switches + Skyworks SKY13358-386LF RF Switches Provides absolute air-gapped physical disconnection of power, data, and antenna lines | Skyworks Solutions, Inc. | 16-XFQFN Exposed Pad | 1 | Matched | |
2 alternatives consideredAI verified | |||||||
| 7-inch Rugged IPS Touch Display | DISPLAY | 7-inch Rugged IPS Touch Display Renders the main cyberdeck interface, waterfall plots, and monitoring telemetry | — | — | 1 | Pending | |
Build guide
6-8 hoursAdvanced
1
Procurement & Preparation
- Source all active components, including BQ25713RSNT, CM4, RTL2832U, SX1262DVK1CAS, RP2040, SKY13358-378LF, and the 7-inch Rugged IPS Touch Display.
- Prepare the custom PCB panelizers, stencils, and cleanroom soldering station for surface mount device (SMD) placement.
2
Hardware Assembly & Wiring
- Apply Type-4 lead-free solder paste to the mainboard and populate the BQ25713RSNT and TPS65987D power management circuit, passing through the reflow oven to establish the 5V/3.3V power tree for the 4S battery pack.
- Mount the Raspberry Pi Compute Module 4 (CM4) onto its designated high-density connectors, then integrate the Realtek RTL2832U + R820T2 wideband RF monitoring frontend via internal USB traces (USB_DP, USB_DM, VBUS, GND).
- Wire the Semtech SX1262 module to the compute core using SPI interfaces (MOSI, MISO, SCK, NSS, DIO, GND) for ISM band packet capture and local RF injection tasks.
- Connect the Raspberry Pi RP2040 to the custom split-matrix mechanical keyboard and wire its USB lines (USB_DP, USB_DM, VBUS, GND) back to the internal USB hub of the host compute core.
- Integrate the DPDT toggle switches and Skyworks SKY13358-378LF RF switches into the power, data, and antenna lines to create absolute air-gapped physical disconnection capabilities (VBUS_SWITCHED, ANT_GROUND).
- Secure the 7-inch Rugged IPS Touch Display into the clamshell housing enclosure and link it to the compute core using HDMI, USB touch lines, and 5V power routing.
3
Firmware Setup
- Flash the custom QMK/VIA firmware onto the Raspberry Pi RP2040 to govern the split-matrix mechanical keyboard and assign macro shortcuts.
- Flash the custom Linux OS image onto the Raspberry Pi CM4 eMMC, configuring drivers for the RTL2832U SDR pipeline and SX1262 packet capture library.
- Configure the TI TPS65987D USB-PD controller firmware parameters for safe 4S battery charging thresholds and strict current-limiting limits.
4
Testing & Calibration
- Perform a comprehensive power-on self-test (POST) while monitoring current draw across the 5V and 3.3V power rails to confirm smooth battery charging and stable power tree generation.
- Activate the physical kill switches and verify complete air-gapped isolation by testing for zero continuity across power, data, and antenna lines.
- Test the wideband RF monitoring frontend across the 24MHz to 1.7GHz spectrum using a known signal generator source to validate waterfall plot rendering and spectrum capture accuracy on the 7-inch IPS display.
- Validate local ISM band packet capture and injection capabilities using the Semtech SX1262 transceiver module within a shielded test chamber.
Document
RF Monitoring Cyberdeck
A compact clamshell cyberdeck designed for RF monitoring and programming featuring complete air-gapped isolation and physical kill switches.
Design Overview
| Item | Details |
|---|---|
| Product Type | RF Monitoring Cyberdeck |
| Key Functions | RF monitoring and programming, Complete air-gapped isolation with physical kill switches, Custom mechanical keyboard input |
| Power Source | Rechargeable internal pack lasting 4-8 hours |
| Connectivity | Air-gapped isolation, Physical kill switches |
| Size | Compact portable clamshell |
| Environment | outdoor |
| Difficulty | Advanced |
| Est. Time | 6-8 hours |
System Architecture
Power Topology: A 4S rechargeable battery pack feeds the BQ25713 charger/power management IC, generating a clean 5V primary bus for the CM4, SDR frontend, and display, alongside a 3.3V rail for low-power MCUs and RF transceivers. Critical power and signal paths pass through manual DPDT toggle switches and solid-state RF switches for hardware kill-switch isolation.
Module List
| Module ID | Type | Name | Function | Voltage |
|---|---|---|---|---|
| POWER_MANAGEMENT | POWER | Texas Instruments BQ25713 + TI TPS65987D USB-PD | Manages 4S rechargeable battery pack, charging, and 5V/3.3V power tree generation for 4-8 hour runtime | 14.8V |
| COMPUTE_CORE | MCU | Raspberry Pi Compute Module 4 (CM4) | Acts as the central host running the primary OS, UI, and SDR processing pipeline | 5.0V |
| RF_SDR_FRONTEND | RF | Realtek RTL2832U + R820T2 | Provides wideband RF monitoring and spectrum capture from 24MHz to 1.7GHz+ | 5.0V |
| SUB_GHZ_RADIO | RF | Semtech SX1262 | Handles ISM band packet capture, LoRa monitoring, and local RF injection tasks | 3.3V |
| KEYBOARD_MCU | MCU | Raspberry Pi RP2040 | Drives the custom split-matrix mechanical keyboard and processes shortcuts via QMK/VIA | 3.3V |
| KILL_SWITCH_DOMAIN | ACTUATOR | DPDT Toggle Switches + Skyworks SKY13358-386LF RF Switches | Provides absolute air-gapped physical disconnection of power, data, and antenna lines | 3.3V |
| DISPLAY_PANEL | DISPLAY | 7-inch Rugged IPS Touch Display | Renders the main cyberdeck interface, waterfall plots, and monitoring telemetry | 5.0V |
Design Schemes
Modular SBC with Dedicated SDR and Hardware Mux ★
Combines a compact industrial SBC for the primary OS, an integrated USB-based Software Defined Radio frontend, a custom RP2040 mechanical keyboard, and a dedicated battery management power tree with hardware kill switches routing through physical relay/switch lines for absolute air-gapped isolation.
Trade-offs: Moderate cost and complexity; excellent flexibility for outdoor SDR tasks; higher power draw requires careful thermal and battery sizing to hit the 8-hour target.
Key IC selection
Battery charger and power path controller
- Need: Manage 4S Li-ion battery charging and provide multi-voltage power rails with USB-PD input
- Class: I2C controlled buck-boost charge controller
- Shortlist: TI BQ25713, Analog Devices LTC4162-S
- Pick: Select BQ25713 for robust SMBus/I2C telemetry integration with TI ecosystem and flexible 1-4 cell buck-boost capability.
Central host processor module
- Need: Execute Linux OS, run SDR applications, and interface with high-speed peripherals via board-to-board connectors
- Class: System-on-Module (SoM) with quad-core ARM Cortex-A72
- Shortlist: Raspberry Pi Compute Module 4, NVIDIA Jetson Nano SoM
- Pick: Select Raspberry Pi Compute Module 4 for its form factor, mature Linux ecosystem, and low power consumption suitable for portable cyberdecks.
Wideband RF receiver frontend
- Need: Downconvert and digitize 24MHz to 1.7GHz RF signals for software-defined radio processing
- Class: Direct-conversion tuner paired with USB demodulator/ADC
- Shortlist: R820T2 + RTL2832U, Analog Devices AD9361
- Pick: Select R820T2 + RTL2832U for cost-effective wideband coverage and massive open-source software support.
Keyboard matrix scanner and macro processor
- Need: Scan custom mechanical keyboard split matrix and communicate via USB HID with low latency
- Class: Microcontroller with programmable IO (PIO) and native USB
- Shortlist: Raspberry Pi RP2040, Atmel ATmega32U4
- Pick: Select RP2040 for high performance, dual-core flexibility, abundant GPIOs, and native QMK firmware compatibility.
RF signal isolation switch
- Need: Provide high-isolation physical and electronic RF path disconnection for air-gapped security
- Class: GaAs pHEMT SPDT RF Switch
- Shortlist: Skyworks SKY13358-386LF, Analog Devices HMC470LP4E
- Pick: Select SKY13358-386LF for low insertion loss, high linearity, and wide frequency range matching the SDR frontend.
Risk register
| ID | Area | Severity | Detail | Mitigation |
|---|---|---|---|---|
| r1 | emi | high | High-density layout placing the high-speed CM4, RP2040, and switching power supplies close to the RTL2832U/R820T2 RF frontend may introduce severe EMI and desensitize the SDR receiver. | Enclose the RF SDR frontend in a dedicated soldered EMI shielding can, use grounded copper pours between digital and RF traces, and ensure proper decoupling on all power rails. |
| r2 | thermal | med | Enclosing a CM4, BQ25713 charger, and multiple radios inside a rugged portable cyberdeck chassis can cause heat buildup during continuous SDR waterfall monitoring. | Design thermal pads connecting the CM4 processor and BQ25713 to the aluminum chassis enclosure to act as a heatsink; evaluate airflow or passive thermal dissipation paths. |
| r3 | firmware | med | Timing conflicts or enumeration issues between the RP2040 keyboard firmware and CM4 host during hard power toggling via the DPDT kill switches. | Implement robust USB reconnection handlers in the CM4 OS and ensure the RP2040 gracefully handles power state transitions without locking up the HID interface. |
Key Components
6/7 modules matched to real parts. See the BOM tab for the full component table.
Texas Instruments BQ25713 + TI TPS65987D USB-PD (BQ25713RSNT)
Exact match for primary MPN BQ25713 (RSNT package variant) from Texas Instruments.
Raspberry Pi Compute Module 4 (CM4) (CM4)
Candidate 1 matches the primary MPN 'CM4' and is manufactured by Raspberry Pi (or associated naming in the catalog), per
Raspberry Pi RP2040 (RP2040)
Candidate 1 matches the primary MPN RP2040 and is manufactured by Raspberry Pi, which satisfies both the MPN and preferr
7-inch Rugged IPS Touch Display (7-inch Rugged IPS Touch Display)
Web recommendation: 7-inch Rugged IPS Touch Display (not in ES)
Build Summary
- Difficulty: Advanced
- Estimated time: 6-8 hours
- Tools required: Solder paste printer, Reflow oven, Hot air rework station, Precision tweezers, Fine-tip soldering iron, Digital Multimeter
See the Build tab for the full step-by-step assembly guide.
Generated by YuanQi AI Design System · Query: building a cyberdeck