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Vlastimil Slinták
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README.md
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README.md
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[![CC BY-NC-SA 4.0][cc-by-nc-sa-shield]][cc-by-nc-sa]
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# LinHT-hw
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Open-source hardware, Linux-based, SDR handheld transceiver. [OpenHT](https://github.com/M17-Project/OpenHT-hw) successor with greatly simplified hardware - no FPGAs involved.
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This project offers a replacement board for the Retevis C62 radio, greatly expanding its capabilities.
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## Hardware
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The device uses an [MCM-iMX93](https://www.compulab.com/products/computer-on-modules/mcm-imx93-nxp-i-mx-93-som-smd-system-on-module) System on Module (SoM) running Linux. The RF front-end is based on the [Semtech SX1255](https://www.semtech.com/products/wireless-rf/lora-core/sx1255). The chip is used as a complete IQ modulator/demodulator, allowing for true all-mode support.
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**Open-source, Linux-based, SDR handheld transceiver**
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### Resources
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**CPU:**
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[![CC BY-NC-SA 4.0][cc-by-nc-sa-shield]][cc-by-nc-sa]
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[](https://m17-project.github.io/LinHT-hw/)
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* Dual-core ARM Cortex-A55 @ 1.7GHz
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* ARM Cortex-M33 coprocessor @ 250MHz
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* Floating Point Unit
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* ARM Ethos U-65 microNPU (Neural Processing Unit with TensorFlow Lite support)
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## What is LinHT?
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**Memory:**
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**LinHT** is an open-source handheld **software-defined radio (SDR) transceiver**
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built around a modern Linux System-on-Module and a true IQ RF front-end.
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* 2GB LPDDR4
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* 32GB eMMC
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It is the **successor of the OpenHT project**, with focus on:
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**RF:**
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* simpler and more maintainable hardware,
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* no FPGA in the signal path,
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* tight integration with Linux, GNU Radio, and modern SDR tooling,
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* long-term openness and hackability.
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* 500kHz bandwidth complete IQ transceiver
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LinHT is developed by members of the **M17 community** and is intended primarily
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for **radio amateurs, SDR experimenters, and developers**.
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## Software
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Developers can use C/C++/Python as well as (or in conjunction with) GNU Radio flowgraphs. Tools such as gcc are built-in.
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This repository contains the **hardware design files** for LinHT.
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### Supported modes (so far):
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> ⚠️ **Important:** LinHT is **not a consumer product**.
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> It is an experimental, community-driven open hardware project.
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* FM transmission and reception with pre-/de-emphasis and CTCSS,
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* SSB transmission and reception,
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* M17 - transmission and reception,
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* TETRA - reception only,
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* Demo 64QAM transmission at 2Mbps
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## Key ideas behind LinHT
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Other modes can be added later (FreeDV, APRS, etc.).
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* **True SDR**: IQ baseband access, not audio-only hacks
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* **Linux-first**: no microcontroller firmware lock-in
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* **No FPGA**: easier development, lower barrier to entry
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* **Open everything**: hardware, software, toolchains
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* **Hackable handheld**: not just another black box HT
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## Images
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## Hardware overview
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### Download images
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LinHT is built around a Linux SoM and a wideband IQ transceiver.
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Prebuilt images for LinHT can be downloaded [here](https://m17project.org/linht/).
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* **System on Module:** [CompuLab MCM-iMX93](https://www.compulab.com/products/computer-on-modules/mcm-imx93-nxp-i-mx-93-som-smd-system-on-module)
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* **RF front-end:** [Semtech SX1255](https://www.semtech.com/products/wireless-rf/lora-core/sx1255)
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### Building images
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**CPU**
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Instructions for setting up the Yocto build environment can be found in the [M17 Wiki](https://wiki.m17foundation.org/index.php?title=LinHT_Image_Build).
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All layers required to build the image are located in the M17 Project GitHub:
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* Dual-core ARM Cortex-A55 @ 1.7 GHz
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* ARM Cortex-M33 coprocessor @ 250 MHz
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* Floating-Point Unit
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* ARM Ethos-U65 microNPU (TensorFlow Lite support)
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- [meta-linht-hardware](https://github.com/M17-Project/meta-linht-hardware): Provides machine configuration and hardware support for the LinHT hardware.
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- [meta-linht-software](https://github.com/M17-Project/meta-linht-software): Provides application software, libraries, and system configuration.
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- [meta-linht-sdr](https://github.com/M17-Project/meta-linht-sdr): A modified version of [meta-sdr](https://github.com/balister/meta-sdr), providing the GNU Radio package.
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**Memory**
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### Flashing
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* 2 GB LPDDR4
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* 32 GB eMMC
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To flash the images to LinHT the [Universal Update Utility](https://github.com/nxp-imx/mfgtools/releases) is needed.
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LinHT needs to be booted into flash mode (holding the secondary side button while booting).
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Once in flash mode, the image can be written with uuu:
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```bash
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uuu -v -b emmc_all imx-boot-mcm-imx93-sd.bin-flash_singleboot linht-image-mcm-imx93.rootfs.wic.zst
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```
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### RF capabilities (revision B target)
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## Driver
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| Parameter | Value |
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| --------------- | ------------------------------------------------------------- |
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| Frequency range | **UHF band** (exact limits depend on PA/filter configuration) |
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| Bandwidth | up to **500 kHz IQ** |
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| Architecture | Direct IQ (complex baseband) |
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| TX power | up to **~5 W** (revision B, internal PA) |
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| RX features | Programmable attenuation, gain control |
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| Modes | FM, SSB, M17, experimental digital modes |
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To access LinHTs network device under windows, [RNDIS driver](https://www.catalog.update.microsoft.com/Search.aspx?q=USB%20RNDIS%20Gadget) need to be installed.
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> 📌 **UHF only**
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> VHF support is frequently requested, but **is not planned for revision B**.
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> The current priority is **stability, manufacturability, and software maturity**.
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## Software overview
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LinHT runs a **custom Yocto-based Linux distribution** designed for SDR and
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embedded radio use.
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### Supported development models
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* C / C++
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* Python
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* GNU Radio flowgraphs
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* SoapySDR
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* Custom DSP pipelines
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Standard Linux tools (gcc, gdb, strace, etc.) are available directly on the device.
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### Supported modes (current status)
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* ✅ FM (TX/RX) with pre-/de-emphasis and CTCSS
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* ✅ SSB (TX/RX)
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* ✅ **M17** (TX/RX)
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* ✅ TETRA (RX only)
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* 🧪 Experimental 64-QAM @ 2 Mbps
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* ⏳ Planned / possible: FreeDV, APRS, packet radio, custom modulations
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## Hardware revisions
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LinHT is developed iteratively. Each revision serves a specific purpose.
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| Revision | Status | Purpose |
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| ---------- | ----------- | -------------------------------------------- |
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| **Rev. A** | Completed | Early prototype, architecture validation |
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| **Rev. B** | In progress | Feature-complete, manufacturing-ready design |
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### Revision A
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* Manufactured earlier in 2025
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* **4 assembled prototype units**
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* Used to:
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* validate the Linux + SDR architecture,
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* bring up SX1255 under Linux,
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* start software and DSP development,
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* identify mechanical, RF, and power issues
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* Revision A was **never intended for production**.
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### Revision B (current focus)
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* Incorporates lessons learned from Rev. A
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* Major improvements:
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* redesigned power supply
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* internal PA (~5 W)
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* improved RF path and attenuation for RX
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* cleaner layout and grounding
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* **Not yet released for manufacturing**
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> 📅 **December 2025 status**
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> Revision B is currently being finalized, manufactured, and tested.
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> Please check this page later for updates.
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## Repository contents
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This repository contains:
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* KiCad 9.0 project files
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* Schematics
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* PCB layout
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* Manufacturing outputs (generated automatically)
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Gerbers, BOM, pick-and-place files, and schematics are:
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* generated automatically via **GitHub Actions**
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* published on [**GitHub Pages**](https://m17-project.github.io/LinHT-hw/)
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## Required hardware (donor radio)
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LinHT is designed as a **replacement mainboard** for the
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**Retevis C62 handheld radio**. You will need:
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* a Retevis C62 (donor device)
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* its:
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* enclosure
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* display
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* keypad
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* battery
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* connectors
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More details (Rev. A focused, older but useful): [LinHT Open SDR Handheld For Radio Amateurs](https://uart.cz/2811/linht-open-sdr-handheld-for-radio-amateurs/)
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## Firmware images
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Prebuilt Linux images for LinHT are available here:
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[https://m17project.org/linht/](https://m17project.org/linht/)
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Documentation:
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* [https://wiki.m17foundation.org/index.php?title=LinHT_Image_Build](https://wiki.m17foundation.org/index.php?title=LinHT_Image_Build)
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Yocto layers:
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* [meta-linht-hardware](https://github.com/M17-Project/meta-linht-hardware)
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* [meta-linht-software](https://github.com/M17-Project/meta-linht-software)
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* [meta-linht-sdr](https://github.com/M17-Project/meta-linht-sdr)
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## Flashing the device
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Flashing is done using **NXP Universal Update Utility (uuu)**.
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1. Boot LinHT into flash mode
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(hold the secondary side button while powering on)
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2. Flash using:
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```bash
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uuu -v -b emmc_all imx-boot-mcm-imx93-sd.bin-flash_singleboot linht-image-mcm-imx93.rootfs.wic.zst
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```
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Tool download: [mfgtools](https://github.com/nxp-imx/mfgtools/releases)
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To access LinHT’s USB network device on Windows, install the **RNDIS driver**: [microsoft.com USB RNDIS Gadget](https://www.catalog.update.microsoft.com/Search.aspx?q=USB%20RNDIS%20Gadget)
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## Documentation & Wiki
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Primary documentation lives on the **M17 Wiki**:
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* [LinHT overview](https://wiki.m17foundation.org/index.php?title=LinHT)
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* [Image build instructions](https://wiki.m17foundation.org/index.php?title=LinHT_Image_Build)
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* [Image usage & manual](https://wiki.m17foundation.org/index.php?title=LinHT_Image_Manual)
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## Contributing
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LinHT is a **community project** and contributions are welcome. The best way to
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get involved is **joining the M17 Discord**, look for channel: **#linht**.
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This is the preferred place to:
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* discuss ideas,
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* coordinate work,
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* ask questions,
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* avoid duplicated effort.
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Other ways to contribute:
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* Open issues in this repository (design notes, questions, suggestions)
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* Help on the **software side** (especially welcome):
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* Yocto recipes
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* device tree improvements
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* CI / GitHub Actions
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* build automation
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* Explore and extend [LinHT-utils](https://github.com/M17-Project/LinHT-utils)
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If you’re an experienced **embedded Linux or SDR developer**, we would love
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your help.
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## FAQ – Frequently Asked Questions
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### ❓ Where can I buy LinHT hardware?
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You currently **cannot buy LinHT as a product**. To build LinHT, you need to:
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* manufacture the PCB yourself (using provided Gerbers),
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* source components,
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* assemble the board,
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* use a **Retevis C62** handheld radio as a donor for:
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* enclosure,
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* display,
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* keypad,
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* battery,
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* connectors.
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This may change in the future.
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### ❓ Is LinHT suitable for everyday radio use?
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Not yet. And maybe never in the "consumer radio" sense. LinHT is currently best
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suited for:
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* developers,
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* radio amateurs comfortable with Linux,
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* SDR experimenters,
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* people who enjoy building and debugging hardware.
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You should **not** expect:
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* plug-and-play user experience,
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* polished UI,
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* certification,
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* warranty,
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* commercial-grade RF compliance.
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### ❓ Does LinHT support VHF?
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**No, not in revision B.**
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VHF support is a **frequently requested feature**, but it is
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**not planned for revision B**, adding another band significantly increases:
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* RF complexity,
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* filtering requirements,
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* PCB area,
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* development time.
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Right now, the project is focused on:
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* stabilizing the hardware,
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* finishing revision B,
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* improving software and DSP,
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* validating the new power amplifier and RF chain.
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VHF is **not ruled out** for future revisions, but it is
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**not a current priority**.
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### ❓ Is LinHT certified / legal to transmit with?
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LinHT itself is **not certified**. Responsibility lies with the builder and
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the operator. LinHT is intended primarily for:
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* amateur radio use,
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* experimental licenses,
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* lab and research environments.
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Always follow your local radio regulations.
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### ❓ I want to help. Where do I start?
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The best starting point is **discussion**. Join the M17 Discord, channel: **#linht**.
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Good ways to contribute:
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* software development (Yocto, drivers, tooling),
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* testing and feedback,
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* documentation,
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* RF/DSP experiments,
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* CI and automation improvements.
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If you’re unsure where to help -- just ask.
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## License
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This work is licensed under a
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[Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License][cc-by-nc-sa].
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This project is licensed under: **Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International**
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You are free to:
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* share
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* adapt
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Under the conditions:
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* attribution
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* non-commercial use
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* share alike
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[![CC BY-NC-SA 4.0][cc-by-nc-sa-image]][cc-by-nc-sa]
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## Acknowledgements
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LinHT is developed by the **M17 community**, with contributions from many individuals.
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Thanks to everyone testing prototypes, reviewing schematics, writing software, and sharing ideas.
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[cc-by-nc-sa]: http://creativecommons.org/licenses/by-nc-sa/4.0/
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[cc-by-nc-sa-image]: https://licensebuttons.net/l/by-nc-sa/4.0/88x31.png
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[cc-by-nc-sa-shield]: https://img.shields.io/badge/License-CC%20BY--NC--SA%204.0-lightgrey.svg
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