Logging/Graphing a Resol Controller via VBus

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Hardware

Note: VBus is not the same as RS485!!! Even if many people say it is, it's not. BUT in many cases, including mine, an RS485 adapter can be used for read-only operation. But thats only a coincidence, if it works, you're lucky, if it doesnt, tough.

I used an old RS232-RS485 adapter I had lying around. When using it with a HugePine USB-RS232-Adapter I had the problem at first that each packet only contained 4-5 bytes and then the transmission terminated and started again with 0xAA. I found that I needed to connect a 9V battery to the +9V input on the RS485 converter to make it work correctly. When I later changed to a Prolific USB-RS232-Converter (from Digitus, 9 EUR on Ebay) I didnt need any external supply anymore.

Software

At first I used the freely available Resol Service Center Software (downloaded from resol.de) but was quickly disappointed by the limited logging/display features and the total lack of graphing availablity. So I wanted to setup a) a device which logs the data 24/7 and b) a way of displaying that data graphically. The only reasonably way of acheiving a) is to use a device which is constantly running anyway. I have a Buffalo WRT-HP-54G WLAN accesspoint/router running DD-WRT and a Buffalo Linkstation Quad, both running Linux, so I decided to use one of those. The Linkstation has more resources and could store data directly to the net drive, so I chose that.

I had already "opened" SSH access with the help of the Buffalo NAS hacking site http://buffalo.nas-central.org/wiki/Open_Stock_Firmware so all I needed was to get a serial interface working on it. Again here 2 possibilities: a) wire up one of the hardware RS232 interfaces which are not connected to any outside connectors (yet), or b) use my USB converter and simply plug it into the NAS. After searching for quite a while, I found matching drivers for the USB serial adapter here: http://ftp.osuosl.org/pub/nslu2/feeds/optware/tsx19/cross/unstable (needed the usbserial and pl2303 modules)

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