Firstly, I go to the XMOS website and get the UART code and play around with it to create the UART code I want (RX only at the moment), compile it and give it a run.

But it’s never that simple! All I get are null characters. Odd I think – so I recheck the wiring, recheck the code. All seems to be ok.

So I strip down the code to a really simple function- one that just receives a character and prints it out (see the Super Simple UART receive function source file)

I still get null characters – maybe I got the wrong pins? Check again… nope, seems fine. So I decide its time to void the warranty (follow these CC128 teardown instructions at your own risk!).

Turns out there is a bit of solder between a via into the ground plane and the UART TX pin on the RJ45 connector (pin 8). After removing this I connected the XC-3 back up to the device and wah lah- it gives me the first character (a ‘<’) of the XML data string.

Now to get the whole string out – so off I go to re-implement the more complex UART code.

After some battling I got it running!

The output looks like the following is in line with the CC128 XML documentation.

Next time… parse the XML and output to somewhere a little more useful!

But that’s boring – time to start hacking!

So, first thing I need is the interface cable. The back of the unit has a handy RJ45 connector that has serial in it (see my initial energy monitoring post). This needs connecting to my XC-3 kit so that I can begin to get the data out of it. So time to get the soldering iron out!

So, initially all I need are two wires from the RJ45 network cable (standard network wiring configuration)-

• Brown = the UART transmit (from the energy monitor)
• Blue = ground

I soldered the rest of them onto the strip board in case I wish to use them later and it keeps things neat and tidy.

For the moment I am using the the GPIO port on the XC-3, using pin 1 for a 1 bit port (XCore UART RX) and pin 16 is ground. This should give a good base from which to work. Eventually I would like to put it on the LED connectors to keep the GPIO free. The other bonus of using the LED connector is that the output side is buffered up to 5V which is what the UART on the energy monitor needs – though I think I will have a check of the Microchip PIC they use inside and see if it will take 3.3V logic levels.

Next time… getting data into the XC-3

More information and pictures after the break…

The basic premise of the system is that data comes in and then goes out the other side (to general traffic the device looks like a wire) and information about that traffic collected on its way through (so at the moment it just looks at packet byte length). The data is then aggregated appropriately with the throughput being averaged over a second (sample at an interval of 100mS).

The information as well as being displayed on screen (via a simple I2C bus) is stored to an SPI flash once every 10s. This is so that if power is lost then the logged data is not.

Current Feature Summary:

• Dual MII ethernet interface
• I2C VFD for showing the resulting information
• Saving of data to on-board SPI flash memory

Future features:

• Internal switch for custom applications (so you can access the device over IP)
• A web interface to allow a user to reset stored data and maybe produce a SVG graph?
• Change display for lower cost, lower power OLED? (Farnell order code: 1498842)

And some pictures:

XC-3 Network Monitor and Display

Network Monitor Display showing a graph and data rates