I recently designed and built a DC barrel jack power supply for a handheld radio. This allows the radio to be used without the lithium battery when there’s external power available, such as at a fixed location or in a vehicle. I also designed a small Type-C charger for convenient outdoor charging, since the stock charger is just a bulky 220V AC desk charger.

I had a macvlan container that required manually running udhcpc inside the container after each startup to obtain a dynamic IP from DHCP. To make things easier, I added supervisord to automatically run udhcpc -f and the container’s own program on startup. After this change, I noticed the container would lose network connectivity after running for a while. Checking the logs, I found that udhcpc would obtain an IP when starting, renew once, and then there were no more renew records.

I recently bought two car battery eliminators online that use the 12V power from a car’s cigarette lighter port to replace lithium batteries, for use with two Baofeng handheld radios respectively. One radio originally uses a 1S 3.7V lithium battery, the other uses a 2S 7.4V lithium battery.

I recently had a requirement to assign different egress IP addresses to each container in a one-to-one mapping. However, these egress IPs are distributed across multiple remote machines and require connecting through different proxies, while the local machine only has a single unified egress IP for external network access.

I recently picked up a few ARM Cortex A8 boards, which appear to be retired Antminer control boards. These boards are modified versions of the open-source BeagleBone Black board, with basically the same PCB layout but with some components removed.

In Hong Kong, ISPs typically provide dynamic public IPs for home broadband through their modem. Modems usually have 2-4 ports, with each port being assigned an independent dynamic public IP.

I’ve been using a phone GPS tracking tool to conveniently record my whereabouts. Traccar is a great open-source software with Android and iOS clients that supports self-hosted servers. The client only uploads location data to your own server, so there are no data privacy concerns. The server also comes with a web interface for managing and viewing device location history.

I recently bought a few RP2040-Zero boards, which are mini versions designed by Waveshare based on the Raspberry Pi Pico. The MCU is the RP2040, and this board even has an extra WS2812 LED and a Reset button compared to the official Pico. However, the ones I bought aren’t actually official Waveshare products, they’re cheaper knockoffs, but they work just the same.

In early 2023, I helped a friend set up a WordPress blog. By mid-2024, he contacted me saying the blog wasn’t loading anymore.

A Web3 hot wallet or hardware wallet can have many addresses. In fact, the wallet only stores one root key, and the addresses we use are generated according to the BIP44 standard, calculated from specified derivation paths based on the root key.