Well, rain has stopped me from working on my camping kitchen project today, so I'll do another DogEars update.
I've chosen my FPGA, I've gone for a Spartan 6 LX9 chip, it seems to be able to fit all the FFT goodness I need with plenty of space left over for any extra magic I need. Big advantages are its a 144 pin TQFP, which if loverly compared to a BGA, so will be simpler to design. Plus its only £15 from Farnell, which isn't too bad for a chip of this calibre.
I've initially decided to use SPI Flash to store the configuration files, but am planning on having it switchable, so the microprocessor can also program the FPGA.
I'm currently working through my main pcb design, I want to basically make it a useful generic pcb, that can be put into a breadboard. I'm trying not to go too mad with it, feature creep is a swine...
So far I'm planning on including:
2 ADCs in and 2 DACs out for the audio conversion, these could be used in the future for any signal conversion, eg sensors etc. I've chosen the Touchstone Semiconductor TS7003 for the ADCs as they are 12bit, 300KSPS and only cost £1.46 each. For the DACs, I went a Wolfson WM8759 Stereo Headphone Amplifier, these are 24bit, 192KSPS and only cost £1.07 each. The Wolfson takes a variety of digital audio signals, for example I2S or AES. The FPGA will have to have this interface coded into it.
Blutooth Interface, which will basically be a header and components for one of the cheap blutooth boards from eBay.
Ultrasound Transmitter interface
A Microprocessor with SD card interface because it may be useful ,plus I'd like to play around with updating the alll the firmware from SD card at some point. This is something I keep meaning to play around with as it will be really useful for other applications.
IO Ports, these will be breadboard pin compatible, I will try to externalise as many pins as possible, you can never have too much IO!
A Highspeed connector for daughterboards. I was getting excited about including things like ethernet, usb, maybe some sort of LCD interface, but this makes the project way more complex than it needs to be, so I decided to put a highspeed connector on the PCB, to allow me to design the other toys on daughteboards at a later date, subject to whatever requirements I need. This is the beauty with having access to such cheap boards from places like Seeed or OshPark, a few years ago these designs would have been too expensive for me to have had made.
In other news, I've stepped into the scary world of GitHub, I'm planning on totally opening up the project, and making schematics, code and gerbers accessible. Check it out, the link is underneath my pictures.
I've also had a quick look at Android programming, with the view to creating an app for this, not sure how complex this will be, its not something I've tried before, but as my brother says, "How hard can it be?".......
If it proves him wrong, I may do a prototype just using python scripting on my phone initially.