The Tool Desk
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What a DIY 4G phone can—and cannot—prove
The OURphone project describes a Raspberry Pi 3 B+ running Raspbian, paired with a Waveshare 4G HAT built around a SIM7600 modem. The Pi communicates with the modem using AT commands. Its feature list includes LTE internet, calls, SMS, contacts, GPS, Wi-Fi, Bluetooth audio, and a 4-inch 480 × 800 touchscreen. Those are the project’s reported features, not independent tests of a new build or proof of reliability for everyday use. OURphone project repository
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The key uncertainty is cellular service. Modem variants differ in LTE bands and capabilities, while carrier requirements and voice provisioning vary by operator and region. The project does not establish current VoLTE provisioning or acceptance by any particular carrier. Treat calls as an item to verify with the exact modem, SIM, and operator—not as a consequence of merely seeing LTE data connect.
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| Route | Best for | Trade-off |
|---|---|---|
| Adapt the OURphone project | Starting from a documented Raspberry Pi and SIM7600 HAT architecture, with project instructions and a reported version 1 completed in 2024. | Check current part availability and carrier compatibility; a project build does not establish dependable daily-use performance. |
| Prototype with a Compute Module IO board | Integrating hardware and using the official IO board as a rapid-prototyping platform and reference design for a possible custom carrier. | A smaller eventual design requires additional carrier-board, power, RF, mechanical, and compliance work. Raspberry Pi’s current documentation covers CM4 and CM5 and recommends them for new designs outside the SODIMM form factor. Compute Module hardware documentation |
| Study the Adafruit PiPhone guide | Learning component roles from an earlier Raspberry Pi cellphone example using a PiTFT touchscreen, FONA, antenna, battery, converter, and headset with microphone. | It is a legacy guide, not evidence of modern LTE or VoLTE compatibility. Adafruit PiPhone guide |
Plan the main hardware blocks
Compute board and software
The Raspberry Pi runs the interface and phone-side software; the cellular modem handles the radio connection. For a quick experiment, a complete project architecture can reduce integration work. For a more integrated design, Raspberry Pi’s Compute Module IO board is intended for standalone prototyping and can serve as a reference for a custom carrier board. The official documentation also covers compute-module and computer hardware considerations. Raspberry Pi computer hardware documentation
#1 Best Overall
- Connected via pogo pin or MicroUSB connector Dedicated pogo pin for Raspberry Pi Zero/Zero W MicroUSB connector for other Raspberry Pi boards or PC
- Incorporates SIM7600G-H global band 4G module, compatible with 2G/3G/4G network with global support. USB HUB connector for other Raspberry Pi boards or PC, providing USB extension and 4G network access
- Supports dial-up, telephone call, SMS, TCP, UDP, DTMF, HTTP, FTP, etc. Supports GPS, BeiDou, Glonass, LBS base station positioning
- SIM card slot, supports 1.8V/3V SIM card. Onboard audio jack and audio decoder for making telephone call
- 2x LED indicators, easy to monitor the operating status. Control via AT commands (3GPP TS 27.007, 27.005, and V.25TER command set)
Modem, SIM, antenna, and carrier
Start by identifying the exact SIM7600 HAT or other modem variant, then check its supported LTE bands against the operator’s network in your location. Confirm the antenna arrangement, SIM requirements, and whether the module and carrier support the voice service you need, including VoLTE where applicable. Ask the operator whether that specific device or modem can be provisioned for calls. A data connection alone does not demonstrate voice support.
Display and controls
OURphone lists a 4-inch 480 × 800 touchscreen; the older Adafruit build uses a 2.8-inch PiTFT. These are examples of display choices, not recommendations that either legacy part will fit a current board. Check display interface, driver support, mounting, touch input, and physical dimensions against your chosen compute board and enclosure before ordering.
Rank #2
- ✅Designed for Raspberry Pi 5, HAT+ standard design with onboard I2C EEPROM, and supports Raspberry Pi 40PIN GPIO stackable expansion. Extends 3x high-speed USB 3.2 Gen1 ports for connecting more peripherals
- ✅Onboard M.2(NGFF) Key B slot, supports SIM7600XX-M.2, SIM82XX and RM5XX series 4G/5G modules and is compatible with 3042/3052 packages. Onboard Type-C port for connecting to a PC for 4G/5G networking, debugging and firmware updating, or external power supply input
- ✅Onboard power monitoring chip for real-time measurement of voltage, current and power. Onboard SIM card slot for NANO-SIM card
- ✅Onboard Reset button, Power and Network indicators for easy debugging and monitoring the operating status. Comes with customized 5G-4IN1-PCB Antenna for neat wiring management, supports top or bottom installation
- ✅Reserved airflow vent and mounting holes for cooling fan to increase airflow and provide better heat dissipation
Power and charging
OURphone describes two 3.6 V batteries converted to 5.1 V DC for the Pi. Adafruit’s guide separately lists a 1200 mAh LiPo and a DC-DC converter. These are distinct project examples, not evidence of runtime for a new phone. Design around the selected board’s input requirements, modem transmit-current demands, and appropriate charging and battery-protection circuitry. Measure the assembled system’s draw under realistic use before estimating runtime; the cited builds do not establish battery life for a modern design.
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Audio, enclosure, and antennas
A usable handset needs a microphone and speaker or headset, user controls, an enclosure, and sensible antenna placement. OURphone lists Bluetooth audio and a 1 W onboard speaker; Adafruit’s older guide includes a hands-free headset with microphone. Those descriptions do not establish audio quality, call reliability, or RF performance in a finished enclosure. Leave room to position antennas and test the assembled device rather than treating the enclosure as a cosmetic afterthought.
Build and verify in stages
- Define the target network. Choose the country and operator first. Verify supported LTE bands, SIM requirements, voice service, and device acceptance for the exact modem variant.
- Bring up the compute board and modem separately. Confirm the Pi or Compute Module boots reliably, then connect the cellular HAT and verify communication with it using the project’s AT-command approach.
- Test network functions individually. Check registration, data, SMS, and calls as separate capabilities. Confirm voice operation with the intended carrier and SIM; do not infer it from LTE data access.
- Add display, controls, and audio. Check that the screen and touch input work with the selected board, then test microphone, speaker or headset, and call controls.
- Integrate portable power and enclosure last. Validate regulation, charging and protection, modem current demands, and antenna placement in the assembled form. Measure current draw under realistic activity before deciding whether the battery meets your needs.
Compatibility, compliance, and practical limits
Do not assume a component’s compliance status transfers to the finished phone. Raspberry Pi says its own products are compliance-tested; its UL94-V0 note applies to its PCBs. Neither statement approves a DIY device assembled with a modem, battery, antenna, display, and enclosure. Applicable radio and finished-product requirements depend on the specific build and geography. Raspberry Pi computer hardware documentation
Quick Recap
Best Value
- Supports 2G/3G/4G network connection, global band.Supports network protocols such as TCP/IP/IPV4/IPV6/Multi-PDP/FTP/FTPS/HTTP/HTTPS/DNS.Driver provided, for operating systems including Windows/Linux/Android
- Onboard USB port, for directly connecting with ARM/X86 hosts or other industrial computer.Onboard UART port with hardware flow control, for connecting with host boards like Arduino/STM32
- Onboard GNSS connecting, supports GPS, Beidou, Glonass, LBS base station positioning (additional GNSS antenna is required but NOT included)
- Nano SIM card slot, supports 1.8V / 3V nano SIM card.3x LED indicators, easy to monitor the working status.Portable customized enclosure, mini size, nice looking
- Baudrate support: 300bps ~ 4Mbps (115200bps by default).Baudrate auto-negotiation: 9600bps ~ 115200bps
Rank #4
- Raspberry Pi & Jetson Nano Compatibility: Features a standard 40PIN GPIO extension header, supporting Raspberry Pi series boards and Jetson Nano.
- Communication Support: Supports various communication protocols, including dial-up, telephone calls, SMS, TCP, UDP, DTMF, HTTP, FTP, and more.
- Positioning and Navigation: Supports multiple positioning systems such as GPS, BeiDou, Glonass, GALILEO, QZSS, and LBS base station positioning.
- USB and Debugging Features: Includes an onboard USB interface for testing AT commands and GPS data retrieval, along with a CP2102 USB to UART converter for serial debugging.
- Additional Features: Equipped with a SIM card slot (supporting 1.8V/3V SIM), audio jack and decoder for telephone calls, 2x LED indicators for monitoring status, voltage translator for 3.3V or 5V operation, and supports autobauding and AT command control (including SIM application toolkit).
- Verify the precise modem revision, regional bands, antenna, SIM, and operator support before committing to a design.
- Check stock and compatibility of every part; the cited project materials do not establish what is currently available.
- Expect to resolve integration issues in power, software, mechanics, and RF. The cited sources do not establish a total cost, finished dimensions, signal performance, or battery runtime for a new build.
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