Reading information from your AMS smart meter #01: Connecting a HAN-to-USB device to your Raspberry Pi

About a year ago, we got one of those new AMS smart meters from Aidon (the Aidon 6525), with an integrated HAN (Home Area Network) port. This port enables me to read power usage stats from the power meter, with a high sample rate so I get close to real time stats. Previously I had to report the energy consumption usage every month, but now it is reported automagically almost in real time (we’re talking every few seconds). This is something I want to explore, to see what I can do with it. Until now I haven’t done anything to try to read values and create my own dashboard at home, but this is about to change.

So what is the HAN port? The HAN port is a simple M-BUS interface, and all Norwegian smart meters must have one HAN port in the physical shape of an RJ45 contact, where only pin 1 and 2 are used for the M-BUS protocol, the other 6 pins are unused. There are several different options for adapters to connect to the AMS smart meter.

Just before the summer vacation, I ordered the HAN port to be opened from my power supplier, and I also ordered a cheap USB-to-MBUS slave module from AliExpress:

While we were away on vacation the module arrived, so it’s time to get this project started. I’ll use a Raspberry Pi Model B 3+ (I’ll simply call it RPi from now on) as the «brain», and connect the module to the RPi. The progress will be slow, as I do not have too much spare time for this, but I want to see this finished as quickly as possible

The first thing to do is to do a fresh install of Raspbian on the RPi. As of this writing, the latest Raspbian version is Raspbian Buster (Raspbian 10). I expect that you know how to install Raspian and boot up the RPi, so I won’t cover this. If you are fresh to Raspberry Pis, you can findt the official documentation here: https://www.raspberrypi.org/documentation/

After installing Raspbian and booting up, remember to secure the installation according to best practices. You can find some good help here: https://raspberrytips.com/security-tips-raspberry-pi/.

So now you have booted your RPi, and it is reasonably secure. Before you try to connect the USB-to-MBUS adapter, let’s see what USB devices are already attached. Run the lsusb command:

$ lsusb
Bus 001 Device 004: ID 152d:0578 JMicron Technology Corp. / JMicron USA Technology Corp. JMS567 SATA 6Gb/s bridge
Bus 001 Device 005: ID 0424:7800 Standard Microsystems Corp.
Bus 001 Device 003: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub
Bus 001 Device 002: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

The first device is my mSata to USB bridge, as I am running my RPi from a mSata disk instead of a SD card. The rest of the devices are the standard RPi devices that are present on all RPis

Let’s attach the USB to MBUS adapter, and see if the RPi will recognise the adapter. Run the lsusb command again after attaching the adapter:

$ lsusb
Bus 001 Device 004: ID 152d:0578 JMicron Technology Corp. / JMicron USA Technology Corp. JMS567 SATA 6Gb/s bridge
Bus 001 Device 006: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port
Bus 001 Device 005: ID 0424:7800 Standard Microsystems Corp.
Bus 001 Device 003: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub
Bus 001 Device 002: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Hey presto! A new USB device has appeared on the list! The USB to MBUS adapter is detected as a «PL2303 Serial Port», which only means that the adapter contains a PL2303 chip to «translate» signals from serial to USB, so the RPi is detecting this as a PL2303. It can’t see what is «behind» the PL2303 interface. This is common for all devices that use a PL2303 chip, so nothing strange.

So how can I communicate with the USB-to-MBUS adapter? It must have some kind of device file that can be used. We can use the command dmesg to find this information:

$ dmesg
[45236.494952] usb 1-1.1.3: new full-speed USB device number 6 using dwc_otg
[45236.627927] usb 1-1.1.3: New USB device found, idVendor=067b, idProduct=2303, bcdDevice= 3.00
[45236.627935] usb 1-1.1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[45236.627939] usb 1-1.1.3: Product: USB-Serial Controller
[45236.627943] usb 1-1.1.3: Manufacturer: Prolific Technology Inc.
[45236.679684] usbcore: registered new interface driver usbserial_generic
[45236.680958] usbserial: USB Serial support registered for generic
[45236.684271] usbcore: registered new interface driver pl2303
[45236.684447] usbserial: USB Serial support registered for pl2303
[45236.684639] pl2303 1-1.1.3:1.0: pl2303 converter detected
[45236.688644] usb 1-1.1.3: pl2303 converter now attached to ttyUSB0

From the dmesg output, we can see that the adapter was detected, and was attached to ttyUSB0. This means that the device can be reached as /dev/ttyUSB0. We need this when we get a little further down the track.

For now, we have a fresh Raspbian install, and a connected USB-to-MBUS adapter. That is it for this post – in the next posts I will connect the adapter to the AMS power meter and see if we can receive anything.

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