This is a DiscontinuedProject. Currently, no effort is made for further work here. I have bought another digital scope (an HP 54502A), which has some storage capabilities. Because of this, the need for a storage adapter for the analog scope is no longer that urgent. If one day I find the storage of the 54502A too small, I might pick this project up again.
I own an old analog Tektronix 465 oscilloscope. With analog scopes, it is hard to do single-shot measurements like, for example, non-repetitive signals. As I am currently doing digital electronic designs for the PinBall project, I often encounter the need for doing exactly such measurements when debugging signals on the control buses there.
As commercial digital storage oscilloscopes (DSOs) are still quite expensive (even the older ones starting at 500 Euro on online auctions), the plan is to build an adapter for the analoge scope I own, able to capture a signal, digitize it, store it in some kind of memory, and replay it to an analog output that will then be fed into the scope for viewing.
This thing will most probably be based on some microcontroller on which I have not yet decided.
Specifications
- Is able to measure an RS-232 line at 19200 bit/second with a resolution of 10 measurements per bit
- This means we need 192'000 samples per second.
- With a vertical resolution of 255 (that is, the signal levels of -15 to +15 V are represented by numbers from 0 to 255 through the A/D converter), this means 188 kByte per second of measurement and storage.
- Furthermore, this means that the microcontroller must be able to do measurements this fast, and store them to memory. It has 5 microseconds per measurement.
- Supports triggering of some kind for its own start of measurement
- Easiest way would be "input signal deviates more an x V from where it was when some button was pressed"
- Supports time axis resolution changes and scroll forwards and backwards through the collected data
- This means, user can set a window of defined length in time and move this through the whole capture, e.g. viewing 0.1 second out of a capture of 0.5 seconds
- Supports at least RS-232 and TTL voltage level inputs
- Delivers a fixed output voltage level (for example, 0 to 5 V, or -5 to +5 V)
- Generates a trigger signal to be used by the analog scope
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