Just a relatively short post this time, as I ease myself back into the blogging habit. In case you are interested; since my last post I have been travelling round the South West of the UK with my family, spending time with friends and relations along the way. Very pleasant to have a break, but the lack of internet was a killer - I came home to a mountain of emails and blog posts to read.

Today seems to have been mostly about porting. I've not really developed anything new, but I have learned a lot by moving things around between machines.

Yesterday I was a little disappointed with the un-tuned performance of the FFT code I had found and got running on the Freescale Freedom KL25Z, so I decided to givce it a go on some other platforms. The first step was to move it to my development PC to see how that stacks up.

Progressing with my attempt to record and process ultrasonic sounds, I have spent this evening with a trial version of a fast fourier transform (FFT) on the KL25z ARM board. My hope is that if I can get it running fast enough and well enough, I can offload that part of the work to this "co-processor", leaving the Raspberry Pi to deal with all the rest of the UI, communications, pattern-matching and so on.

Despite a head buzzing with ideas for things to do with the interesting combination of Raspberry Pi and Freescale KL25z, I had no time to play with them this evening. I had a meeting to go to!

I mentioned in my discussion of the Ipswich technology scene that I had discovered a group of people trying to get a local Hackspace off the ground. I joined their facebook group and it reminded me that there was a meeting this evening at local pub and popular techie meeting place The Brewery Tap. The meeting was supposed to start at 8pm and I arrived ten minutes or so early, so I took the opportunity to get myself a pint.

In my continuing quest to get ultrasonic sound information in to a Raspberry Pi so I can do interesting stuff with bat sounds, one of the candidate devices I have identified is the Freescale Freedom KL25z board. Unlike the MCP3002 that I tried to connect to recently, this is not just an analogue to digital converter. It's actually a whole single-board ARM development system, with an ARM Cortex M0+ Core running at 48MHz, 16KB RAM, 128KB FLASH, 2xSPI, 2xI2C, 3xUART, 6xPWM, 6xADC, lots of digital GPIO, 3-axis accelerometer, PWM Controlled RGB LED, and a Capacitive touch sensor. Arguably it's more powerful and flexible than an Arduino, and cheaper too.

The more I think about it, the more fascinating the possibilities of the Raspberry Pi become. It occupies a really interesting spot between traditional embedded controllers like Arduino, pics and the like at one end, and "proper" computers at the other. It has enough GPIO to do some of the things the embedded controllers can do, yet it has the memory, processing power and network connectivity of a (albeit low-end) much larger computer. And all at a price which makes it easy to consider buying more than one and using them each for separate purposes.

"Pirates and SPIs" sounds like a cheesy adventure story, but I'm afraid it's more likely to be a serial than an exciting drama.

A few days ago I had a delivery of some components I had ordered, including a MCP3002 analogue to digital converter. The data sheet for this device claims that it can do 200k samples per second (when powered at 5V) and it has a high-speed SPI interface so it should be fairly strauightforward (probably with the use of some level converters) to wire it straight to the Raspberry Pi SPI pins.

I have had an Arduino board sitting in one of my electronics boxes for months. While chatting with an ex colleague yesterday evening, it occurred to me that I had never actually done anything with it. Although it may seem that Arduino and Raspberry Pi are in some sense competitors, I'm seeing more and more projects which use the best features of both devices to make something "more than the sum of the parts". The Gertboard (which I have also never got around to doing anything with yet) has an on-board AVR microcontroller, as do several others. "Zoe", the retro-cased hydroponic garden controller which I saw at the Norwich group also used a combination of the two devices.

No playing with Raspberry Pi hardware this evening. Instead I went out into the real world and actually talked to people! Of course some of that talking ended up being about Raspberry Pi, Arduino and the like...

I live in Ipswich, the county town of Suffolk, and the reason for all this exercise was the inaugural meeting of Sync Ipswich. In their own words:

SyncIpswich is a community of developers, designers, leaders, entrepreneurs all with a common love of technology and making things happen. We welcome anyone who loves technology, has start-up ideas, wants help, wants to hangout with like-minded & passionate people.

I suppose I should know better than to announce what I plan to do the next day. In yesterday's post I made a lot of progress with the HotPi board and was looking forward to having fun with colour LED control and IR sensing. Unfortunately I made hardly any progress, and ended the evening not really any further ahead than I was.

As far as I can tell, it's not really a problem with the hardware, it's just that the combination of work-in-progress documentation and trying to use the board on a system different from the one used by its creator led to a lot of frustration.