Testing USB serial relay compatibility with Mikrotik RouterOS - Fail

I've got some Amateur Radio projects in the pipeline that will require the ability to turn off the radio remotely in the event of a fault developing. This needs to be out-of-band and accessible to more than one "closedown-operator" so if the main operator isn't available, someone else can shut the station down.

The projects all require a computer of some sort, so I had an idea that I could use a USB serial relay to switch the power to the radios off, assuming they'd be easy to use and compatible with both standard form factor PCs as well as SBCs like Raspberry Pis.

I quickly realised this wouldn't be ideal as the situation might arise where the computer has crashed and left the radio transmitting, and it wouldn't be possible to switch off the relay, so I needed an alternative. As it happens I was also planning on including a Mikrotik router in these builds as they've gained the nickname "The Swiss Army Knife of Routers" and allow you to quickly setup tunnels and VPNs which are useful for remote access. Some models also have a USB port, and basic support for USB serial adapters, so I bought a few from AliExpress to test them out.

USB Serial Adapters


Flashing MMDVM on an STM32 Nucleo using Raspberry Pi OS 11 / Bullseye

5 years ago I wrote a blog post on Flashing MMDVM onto an STM32 Nucleo with OSX. Well, good news patient readers, I'm back with a new post, this time doing the flashing from Raspberry Pi OS 11 / Bullseye.



GPS over 75 Ohm Satellite Cable

I needed to get a GPS signal for a couple of upcoming projects that use it for time synchronisation. The problem? Where I intend to place this equipment happens to be a windowless cupboard in the middle of the flat, and the metal roof blocks out the GPS signal. 

However! The original builders ran satellite coax cable to each of the bedrooms and the living room and terminates in said cupboard, along with two feeds from the communal Satellite distribution, allowing you to "patch" services as you require. I'm curious how many residents have discovered this as its all hidden behind a blank face plate, but it has previously came in handy when I wanted to mirror the Satellite reciever to the bedroom and ended up with a rather hacky, HDMI over Ethernet over Coax solution with cheap boxes from China that effectively ran powerline over the Coax cable.

But GPS receivers are expecting 50 ohm coax, not the 75 ohm cable used for television distribution. Will it work?


Creating your very own 56K Dial Up Internet connection in 2022

I've recently been bitten by the analog telephony bug (again) and thought I'd have a go at creating a dial up Network Access Server (NAS).  After some trials and tribulations and with the help of some great people online I've managed to get it working, and once again heard the glorious sounds of a dial up modem connecting to the internet... to quickly discover that bloated web pages make the experience even slower than I rememeber.

If you too are desperate to hear the screech of a dial up modem (and the drone of a Cisco router) you can build a setup for around £100

US Robotics Modem


Measuring central heating return temperature with ESPHome, Home Assistant, and a Inkbird IBS-TH1

I'm currently renting and the boiler in my flat is old and lacking smarts. Last year I had a Drayton Wiser Thermostat installed which I'd highly recommend to people doing smart home stuff. The native app is tolerable, but it's takes minimum effort to get it working with Home Assistant, a popular home automation platform. Home Assistant allows me to do things like automatically set away mode when the house is empty, and also gather some metrics like when the boiler is actually on ( Or at least, the thermostat is calling for heat ), and if someone has fiddled with the thermostat...

One of the Wisers strengths is an intelligent, PID controller like operation that switches the heating on and off fairly frequently to prevent overshoot, and it does a good job at keeping the temperature relatively stable. But I'm curious how the seemingly short cycles affect the temperature of the water in the system, so I'd like to collect some more metrics on the return temperature and eventually the flow and hot water pipes if it works out.


Inkbird IBS-TH1 Sensor




M5Stack Atom Lite + esphomeflasher = "Error: Reading chip details failed: Timed out waiting for packet header"

I recently purchased a M5Stack Atom Lite ESP32 module to use with ESPHome. It wouldn't flash with the browser, so I downloaded the binary and attempted to upload it with esphomeflasher, but it failed with the error "Error: Reading chip details failed: Timed out waiting for packet header" on every attempt.

Fortunatly I found a work-around.


Mikrotik RouterOS - "received unsupported protocol 0x2145"

I've recently been playing with L2TP tunnels between Cisco and Mikrotik gear in an LAC/LNS type configuration. The L2TP tunnel was coming up but any traffic across the tunnel would fail. Enabling l2tp logging on the Mikrotik router revealed the error "received unsupported protocol 0x2145"

Google didn't give any direct solutions but did give a few clues suggesting it might be related to "Protocol Field Compression" (PFC),  and reading RFC 1661 yielded a bit more information on how it should work.

Fortunately I was able to find a fix.
A Mikrotik bug? Never!