In my excitement to write about attending my first Raspberry Pi meetup yesterday, I forgot to say anything about what I actually got up to myself. In between chatting and finding out about other projects I did make some progress on mine.

In quiet moments I hacked on the ELIUS code to get the remaining tests working following the move to a unified memory heap, and pushed the final code to the master branch on github. The code now uses a single linked heap for both dictionary definitions and string pool. Moving over the other data areas and values is still to follow, but the code is already simpler, with fewer system variables needed.

I also spoke to several people about my “bat detector” project, and got some really interesting suggestions. Someone pointed out that 192KHz audio input is pretty much a standard for pro audio equipment, and suggested that there might be usable chips or boards already available which I could use to get the high-frequency sounds into digital form for processing. Someone else suggested I look at Software Defined Radio (SDR) – even though radio is typically much higher frequency than I am interested in, apparently a lot of SDR systems heterodyne the RF signal down to a more reasonable 200KHz or so for processing.

Finally, a few notes to myself on things I have learned from attending this meetup.

• Take plenty of cables. Everyone seemed short of cables (USB, network, power…), and I hadn’t even brought an ethernet cable, so I had to connect to my Raspberry Pi using a serial adapter.
• Take a wifi/network hub. Although there was wifi available, one participant wanted to set up a small local network with laptop and pi, but the lack of DHCP made everything much more complicated
• Take a small toolkit. Although I got away with it this time, I felt naked without even a screwdriver or pair of pliers.
• Take more photos. When I got home and went to blog about the event, all I had was one image from instagram.
• Check my kit before I go. I hunted through the stuff I had taken several times before giving up and admitting I had left the Freescale Freedom board at home.
• Fix the pins on the serial cable into a single connector. I loose track of the number of times I have had to look up which wire goes to which pin to talk to the raspberry Pi UART.
• Label those darned SD cards. Even though I wrote about this ages ago I still haven’t done it, so I still get baffled by what’s on each card.