View source for LinHT

[[File:Linht outdoor.png|thumb|LinHT, as seen in the wild]]
Open-source hardware, Linux-based, SDR handheld transceiver. OpenHT successor with greatly simplified hardware - no FPGAs involved. This project offers a replacement board for the Retevis C62 radio, greatly expanding its capabilities.

= Hardware =
The device uses an MCM-iMX93 System on Module (SoM) running Linux. The RF front-end is based on the Semtech SX1255. The chip is used as a complete IQ modulator/demodulator, allowing for true all-mode support.

= Resources = 
=== CPU: ===

* Dual-core ARM Cortex-A55 @ 1.7GHz
* ARM Cortex-M33 coprocessor @ 250MHz
* Floating Point Unit
* ARM Ethos U-65 microNPU (Neural Processing Unit with TensorFlow Lite support)

=== Memory: ===

* 2GB LPDDR4
* 32GB eMMC
* 500kHz bandwidth complete IQ transceiver

=== Software ===
Developers can use C/C++/Python as well as (or in conjunction with) GNU Radio flowgraphs. Tools such as gcc are built-in.

=== Supported modes (so far): ===

* FM transmission and reception with pre-/de-emphasis and CTCSS
* SSB transmission and reception
* M17 - transmission and reception
* TETRA - reception only
* Demo 64QAM transmission at 2Mbps

Other modes can be added later (FreeDV, APRS, etc.).

=== Images ===
Prebuilt images for LinHT can be downloaded [https://m17project.org/linht/experimental/ here].

=== Building images ===
Instructions for setting up the Yocto build environment can be found on [[LinHT Image Build|here]].

=== Flashing ===
==== Standard: using the Universal Update Utility (''uuu'') ====
To flash the images to LinHT, the [https://github.com/nxp-imx/mfgtools/releases Universal Update Utility] is needed. LinHT needs to be booted into flash mode (holding the secondary side button while booting). Once in flash mode, plug in the USB-C cable, then the image can be written with ''uuu'': 

<syntaxhighlight lang="bash">uuu -v -b emmc_all imx-boot-mcm-imx93-sd.bin-flash_singleboot linht-image-mcm-imx93.rootfs.wic.zst</syntaxhighlight>

==== Alternative: mounting the eMMC drive ====
Sometimes, the ''uuu'' tool fails to flash the image. It will then exit at 15% (or at some other point) with ''libusb'' returning error -1 or -9. Luckily, there is another way to flash the device. Its eMMC drive can be mounted using debug UART exposed at the Kenwood connector. The connection parameters are as follows: 115200 baud, 8 bits, no parity, 1 stop bit, CR-LF line ending.

After putting the LinHT into USB boot mode (and USB-C plugged in), connect a USB-UART converter (3.3V logic!) at the Kenwood connector. Issue a U-boot command to mount the eMMC drive:
<syntaxhighlight lang="bash">ums 0 mmc 0</syntaxhighlight>
A new drive should appear (looking like an external flash drive). Then, a tool like ''dd'' or Rufus (under Windows) can be used to flash the image:
<syntaxhighlight lang="bash">zstdcat /path/to/image.wic.zst | sudo dd of=/dev/sdX bs=1M status=progress</syntaxhighlight>
where ''/dev/sdX'' is the eMMC's mounting point.

====Updating the image====
To update the image, use SSH to execute
<syntaxhighlight lang="bash">fw_setenv bootcmd "setenv bootcmd '`fw_printenv -n bootcmd`'; saveenv; ums 0 mmc 0"</syntaxhighlight>
then
<syntaxhighlight lang="bash">reboot now</syntaxhighlight>
This command tells U-boot to mount the eMMC drive at next boot. The device will reboot. It is now possible to use ''dd'' or Rufus with the freshly mounted eMMC to flash the Linux image (see above). After flashing, unmount the drive and reset the device to complete the process. The ''bootcmd'' variable will automatically be overwritten with its original contents, such that after reset the device will boot Linux normally.

'''Note:''' this method does ''not'' update the boot partition (which includes the device tree).

=== Driver ===
To access LinHTs network device under windows, RNDIS driver need to be installed. You can use for example [https://wiki.sipeed.com/hardware/en/maixsense/maixsense-a075v/install_drivers.html this one] (Not provided by the LinHT team! Use at your own risk!)

It should work on most Linux distributions out of the box!

= Links =

=== How-tos ===

[[LinHT Image Build|LinHT image build]]

[[LinHT Image Manual]]

=== Blogs ===

[https://m17project.org/?s=linht M17Project.org]

[https://uart.cz/en/2811/linht-open-sdr-handheld-for-radio-amateurs/ uart.cz]

[https://www.zeroretries.org/i/172905621/linht Zero Retries]

=== Presentations ===

[https://github.com/M17-Project/M17_education/blob/main/English/M17_Con_2025/M17_Con_2025_LinHT.odp LinHT – a GNU Radio configurable handheld transceiver] (en), Wojciech Kaczmarski (SP5WWP), M17 Conference 2025 ([https://www.youtube.com/watch?v=ecn54XRD5Oo video])

[https://www.youtube.com/watch?v=PyispKXU68Y LinHT: open-source SDR transceiver] (cz), Vlastimil Slinták (OK5VAS), OpenAlt 2025

= Repositories =

=== Hardware ===
[https://github.com/M17-Project/LinHT-hw Main LinHT-hw: LinHT hardware repository]

[https://github.com/M17-Project/LinHT-rf-amp LinHT-rf-amp: GRF5604 Test board]

=== Software ===
[https://github.com/M17-Project/LinHT-utils LinHT-utils: Collection of LinHT tools, scripts and flowgraphs]

=== Yocto layer ===
[https://github.com/M17-Project/meta-linht-software meta-linht-software: Installed software, configuration, ...]

[https://github.com/M17-Project/meta-linht-hardware meta-linht-hardware: Device Tree, driver, ...]

[https://github.com/M17-Project/meta-linht-sdr meta-linht-sdr: GNU Radio packages]

= License =
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

CC BY-NC-SA 4.0

[[Category:Hardware]]
[[Category:LinHT]]