Scrolling text on oscilloscope, built with only one component: the Microchip PIC16F628A. The characters to be displayed are stored in EEPROM (ascii codes from 0x20 to 0x5f so numbers, capital letters and special characters). The first Eeprom location with 0xFF value is considered as end of text. The last Eeprom location (addr 0x7F) contains the scrolling speed in 20mS steps. The configuration word for this application (address 0x2007) is 0x3F34. After programming the micro via the ICSP connector, place a jumper between the pins VDD and VPP (reset input tied to Vdd). The oscilloscope will be set for 2mS/div on X axis and 1V/div on Y axis. One full screen contains 10 characters.

The principle is simple: I just use a 4 (or 5) bit DAC to send a sawtooth waveform (modulated) on the Y axis of an oscilloscope. The X axis is normally driven by the oscilloscope itself and the "character line" is triggered by a single pulse sent before the ramps.

The very first application of this "strange" display was in a commercial product that I did in the past for my company. It was a palm device, going in low power mode. I needed a tool to see what happened in internal registers when in low power mode (at 32KHz clock) and so I used a resistor DAC (very high Ohm values) to create a scrolling text with all the register showed while running. I published this project on my (very) old sites in the past and I know that it has been cited in an University thesis by some jung student. Also it has been cited by HackADay (thanks!) and some other people that made similar devices using this approach.

The circuit is very simple! Just the ic, the battery (obviously) and wires:

You can download the firmware here: http://ficara.altervista.org/wp-content/uploads/2012/11/ef140.zip and read the full article here: http://ficara.altervista.org/?p=1176 . Another example is here: http://ficara.altervista.org/?p=1501. This uses an ATMEL micro and a very simple resistor DAC.

Here is a video on youtube: