DSO Block Digram

Here's a little block digram I did up to help me work out the best way to connect the ADC(s), RAM and CPU. If anyone out there has any suggestions please leave a comment.

DSO Revelations

So today while doing the thoroughly mentally stimulating task of watering trees at work all day I had an epiphany. I am building a Digital Storage Oscilloscope ie. I can have 2 programs that run and have them mutually exclusive. A capture program that reads the state of the ADC(s) and pushes them to a more stable memory location(seperate section of RAM, Main HDD[my be a section of flash memory on board] or Dedicated section of Flash memory). The pseudo-code for this would be along the lines of:
Reset counter
While Stop = False do

Move state_of_ADC to register0 Move register0 to Permanent_Location[counter] counter = counter +1

EndWhile

This would give a sampling rate that can be calculated fairly easily. The instructions are fairly basic so they should each only take 1 cycle to execute. Therefore 5 cycles are required to monitor the state. Therefore we just divide the clockspeed of the CPU by 5 to give us the sampling frequency(assuming CPU at 1GHz):

1GHz/5=200MHz

That's a 200MHz sampling rate. The only problem with this method is that the only real way to change the sample rate is to change the CPU's clock speed... But if I'm going to build a radio from scratch then I dare say I'll get used to adjusting frequencies with a voltage...

The other program would be a GUI that allows the "settings" to be adjusted and a graph to be displayed. The "settings" would only effect the display. Unless I decide to implement software controllable attenuation or something useful like that. The attenuation would be done before the ADC and would be instructed to attenuate through the communication bus from the ADC which is activated for reverse transmission by sending a pin to say -5V which shouldn't happen in any other situation.

Anyway is anyone finds this helpful/instructive/wrong don't hesitate to leave a comment, more comments inspires me to write more :)

p.s. If anyone sees the HTML tags wrong or wants me to go through the tags I used here let me know any I'll put something up.

Laptop Oscilloscope original state

Here are the photos as promised yesterday. I apologise for the quality but my iPod 4G was pretty much the only camera that functions reasonably well and reliably.

 The basic overview. The tag in the back right corner is a repair tag from when grandpa got it fixed at some stage.

 A view of the screen, keyboard and mousepad. the screen and keyboard should be re-usable but I'll need to find a new mousepad and buttons.

Some views of the bottom. At bottom with all of the removable sections partly removed. Clockwise from top right there is the CDROM drive, HDD bay, Floppy/Zip drive bay.

Here all of the removable modules are removed. Bottom left we can see the modem module with broken ribbon cable from a previous teardown I did.

 Here is the backplate with (L to R) VGA out, RS-232, 2xUSB, proprietry breakout plug, RCA video out, S-Video out, Printer port.

 2.5" HDD bay.

 CDROM sitting on top of HDD bay to get some angle on the front.

 Zip and Floppy drives side by side on top of HDD on top of CDROM, once again for some angle.

 A close up of the connector. Should be pretty easy for me to put in my own connectors.

 The where the battery was. It's a pretty big hole and a raspberry pi would probably fit in this space alone. Maybe some other pluggable module... Perhaps a replaceable CPU/RAM module or something.

The battery in all it's brick-like glory. It doesn't work as a battery anymore but if I did want to I could probably re-pack the original cells... Perhaps even increasing the capacity. :)

If you want any more detailed pictures or info post a comment and I'll get some for you.

Finally... New project :)

Finally I've decided what to make my next new project. A DSO... This oscilloscope will be housed in the case of an old laptop that was given to me a while ago by my grandfather after they got a much better one. From memory it's current specs are in the vicinity of: 400-500 MHz processor(Pentium?), 64MB RAM, 4GB 2.5" IDE HDD, broken mousepad, decent screen (will run up to 1024x786?), came with win98, struggles to run cron, X11 and a window manager(twm?) on top of a CLI Ubuntu install.

All this will be replaced allowing me to start from scratch... I will probably keep the keyboard and screen, even if I have to set up an AtTiny or similar to get the interfaces in a format I want. At this stage looking at using an ARM processor or SoC. The CDROM bay will be replaced with pluggable modules with a digital interface to the main board allowing me to change and upgrade input channels or make a computer controlled function generator/DSO that can be controlled from any computer (Running Linux of course :) ). At this stage to allow remote control ethernet/WIFI is planned with an interface probably built from Qt. As well as being remote controllable the oscilloscope will be locally controllable, with the bootloading being handled by coreboot with a linux kernel payload.

I want to be able to use this to help me debug amateur radio rigs up to the 40m band to start with. The pluggable ADC modules allow me to improve if I need better frequency/accuracy. Basic features will include:
-Local control to allow full functionality as a normal DSO.
-Updatable firmware so new features can be implemented.
-Miniumum 50MHz bandwidth for initial product(excluding prototypes).
-Network connectivity to allow remote monitoring.
-Possibly battery, to allow monitoring in locations with limited power outlets
-Using only free and open source tools to design and sharing the designs as open source(github?)

Hopefully soon I'll get a picture of the laptop in it's current condition so you can get an idea of how much space internally I have to work with :)