Hootoo + OpenWrt + Velleman K8055N

One of the things that I had kicking around at home was a Velleman K8055N (actually mine was the pre-made version, the the VM110N) - but I think they are essentialy the same thing. I decided that it would be really cool to try it out on OpenWrt ... so that eventually I could try interfacing a tiny embedded Linux machine with the outside world.

Some quick googling led me to this driver which I tried on a Debian Virtual Machine first, and then decided to run it on my Hootoo HT-TM02. I used a docker container to build the kernel module according to the instructions, and then copied it over onto the device for installation.

The first attempt at installing the module gave the following error:

Collected errors:
 * satisfy_dependencies_for: Cannot satisfy the following dependencies for
 kmod-k8055d:
 * 	kernel (= 3.18.23-1-e2416fa0abee73ea34d947db4520f4e9) *

Which I assumed was just OpenWrt being a bit over cautious, because I was actually running kernel v3.18.23. So I took the risk and overrode the error, with this command:

opkg install /tmp/kmod-k8055d_0.2.1_3.18.23-ramips-1_ramips_24kec.ipk --nodeps

Perfect, it worked! So the K8055N is now accessible in the file system under /proc. To celebrate, I hooked up the digital-to-analoge converter to an old voltmeter, so I could watch the needle bounce around in response to what I'm typing on the command line:

I think that's pretty awesome, although I don't know what I'll use it for. Perhaps I'll build some kind of Web API and allow inputs and outputs to be controlled from a browser. Or ... come to think of it, I could build a really cool CPU meter with the output showing via the needle of the voltmeter.

Hacking your Hootoo

For my wedding anniversary this year, my wife bought me a Hootoo HT-TM02 (amongst other things). How nerdy is that? But it's a nice little machine which can have the default firmware replaced with OpenWrt. For about USD $16.00 it's a very cheap way to have an embedded Linux machine. Personally, I didn't even try the standard firmware and put OpenWrt on straight away. It was pretty easy, but you need a USB stick to give the device some extra storage during the initial upgrade process. The instructions are here and the process was very smooth.

As soon as I had the initial OpenWrt installation, I decided to switch to trunk OpenWrt, so I used the sysupgrade command to install the 15.05 trunk image from here. So this left me with a device running trunk OpenWrt. I then held the reset button in (whilst the device was powered on) for 30 seconds to make sure that the configs were all at default settings.

Next, I decided to install relayd to bridge the LAN (ethernet) port with my existing Wi-Fi network. I followed the instructions here and that seemed to work fine. I felt that I had followed those instructions exactly; but the OpenWrt firewall was still getting in the way. So I just went ahead and disabled the firewall by using:

/etc/init.d/firewall disable

After doing that, I can switch off the Wi-Fi on my laptop, connect a network cable between the Hootoo and the laptop and I'm on my network. The Hootoo is acting as a bridge between my own Wi-Fi and its own ethernet socket, very nice!

The next thing I need to do is cross-compile some code and get it running on the Hootoo.

An update to my 'rCPU' remote monitoring webserver

I thought that it was about time I had a fiddle with the tool I made to remotely monitor CPU use. I have mainly been using it on my Raspberry Pi 2. I switched the javascript library from Smoothie Charts to Flot, in the hope of getting better browser support. But I was able to take advantage of some features of flot at the same time. So this is how it looks now:

That clip was recorded by remotely monitoring my Raspberry Pi 2 from my MacBook. Hopefully it's a worthwhile improvement. The code is all on GitHub: davidsblog/rCPU.