AlanSite

Build a CAT for ICOM rigs with CI-V and Soundcard interface

I’m recently interesting on FT8 and other digi modes, and willing to make a high quality, fully isolated CAT adapter. So here it is. Using FT232RL and PCM2902 for CI-V and ACC audio interface, and the FE1.1s USB hub to tie them together on a single USB type B socket. The audio is isolated by two 600:600 audio transfomer and the CI-V interface with PTT is isolated by optocoupler, in order to block the protential RFI which may take the USB link down, also SMD ferrite beams are put on every pin at the rig side help blocking the RFI. Read more

2026-08-11 HAM

Stop using Mix43 ferrite toroid, and why so

The mix 43 ferrite is commonly known in HAM usages, for chokes and transformers (balun or unun). However, the choosing on this type of ferrite is actually a compromise made by the days that old HAMs could not get better toroids in a reasonable price. Read more

2026-08-06 HAM

Some commonly used amateur radio quick reference tables

Some useful or insightful data and quick reference tables about amateur radio like: The distance of one hop propagation from layer F2 Read more

2026-07-16 HAM

Engage Disk Encryption with LUKS and systemd-cryptenroll on Linux

The TPM, Trusted Platform Module, is well-known by the forced requirements of Windows 11 and automatic Device Encryption aka Bitlocker, which makes lots of people lose they data. However, using a TPM is the best way to protect your digital world in modern times. It’s basically a smartcard mounted on the system, in major, accept hash to ‘extend’ (like NEW = HASH(OLD + PROVIDED)) internal SHA PCRs (Platform Configuration Register), and release key when the PCRs are as same as the key registered for. When the system is booting, the ucode in CPU measures the ucode it self, the UEFI firmware, and the Secured Boot state into the TPM, then pass system control to UEFI firmware. The PCRs can be only reset to zero on the platform hardreset. Read more

2026-04-08 Cryptography

Raise a self hosted PKI (CA) on JavaCard using IsoApplet and OpenSSL

We have handle the fundamentals to JavaCard in last two articles, and completely setup a decentralized cryptography system (OpenPGP). So, in this, we’re going to raise up out PKI (CA) system so that we can issue certificates such as TLS and PIV on our JavaCard. The security and reliability of asymmetric cryptography depends crucially on the confidentiality of the private key. While the public key can be sent to anyone, it is absolutely important that the private key is not compromised. Smartcards have its own processor, RAM and even operating system. They are hermetically sealed from the rest of the system (i.e. the host computer that might be compromised). Also, the developers and manufacturers of smartcards take a huge effort to ensure that no confidential data can be extracted from the card when it is not intended, even by using costly and time-consuming methods such as electron microscopy. Read more

2026-03-22 Cryptography

OpenPGP, PIV, FIDO, NDEF on NXP J3R180 JavaCard and usage principles to ensure safety

In fact, in modern cryptographic systems, the most insecure element is humans; therefore, secure usage guidelines are essential. There’s a joke that describes this scenario: : What if I lose my key and an attacker knows my PIN? : The attacker is you. Do it better next time. Read more

2026-03-18 Cryptography

Introduction to JavaCard and Futhermore (NXP J3R180)

Simply Saying, JavaCard is a kind of SmartCard with JavaCard VM, which can run any JavaCard applet.The opening of Java Card specification makes JavaCard really easy to program instead of old-style Proprietary CPU Card that requires signing up for NDK. In that case, due to the cost of sharing their confidential documents, technical support and production, most of the Manufacturers will not even make a contract with you a little company!So that the JavaCard is the only way we can customize and program SmartCard as safe as CC EAL6+ at low cost. Read more

2026-03-16 Cryptography

Remote Control Relay Based on ESPHome and ESP8685

Driven by the lazy to turn off the lights when in bed, an attempt was made to upgrade the existing lighting fixtures to be intelligent. Choose ESP8685-WROOM-3 (i.e., ESP32-C3), the smallest vertically mounted ESP32 module, was selected. The power supply section uses an LS05-13B05R3 flyback module. Read more

2026-03-03 HomeAssistantEmbedded

Raise a selfhosted translation LLM as systemd daemon

Firstly, spawn a regular llama-server. Read more

2026-03-03 LLM

Make a Bluetooth LE Coded PHY BTHomev2 Temperature and Humidity Sensor Using nRF52832

Since deploying Home Assistant, I’ve been compelled to measure and automate everything, so I urgently wanted to create a Bluetooth sensor. This project also marks my first attempt at using nRF and Zephyr with low-power optimization. The schematic is quite simple — just an nRF52832 and an SHT4x sensor, powered by a CR2032 battery. Therefore, stacking capacitors are needed to prevent restarts caused by voltage drops due to high internal resistance at low temperatures. Read more

2026-03-02 HomeAssistantEmbedded