Once again I'm inspired to go and build a circuit by yet another great tutorial from w2aew.

This circuit generates a stairstep waveform by an ingenious combination of 3 circuit elements:

• a "high" (265Hz) frequency pulse (555 timer) provides the charge to step-up the output
• the step pulse feeds an OpAmp pulse integrator/accumulator
• a low frequency pulse generator (OpAmp oscillator) provides the reset pulse that clears the accumulator and resets the 555

As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub.