Patent ID: 8577316

Claim:
A mechanically tuned radio, comprising: a mechanically adjusted circuit being controlled by a manual adjustment mechanism, the mechanically adjusted circuit comprising: a variable resistor having first and second terminals and a variable tap node, the variable tap node being controlled by the mechanical adjustment mechanism; and a capacitor coupled to the variable resistor; audio output circuitry; power supply circuitry; an antenna, and a receiver integrated circuit coupled to receive a voltage supply from the power supply circuitry, coupled to receive a signal from the antenna, coupled to the mechanically adjusted circuit, and coupled to provide audio signals to the audio output circuitry; wherein the receiver integrated circuit is configured to determine a setting for the mechanical adjustment mechanism through time measurements of the mechanically adjusted circuit, and is further configured to use the setting to select a tuning frequency for the mechanically tuned radio; wherein a first terminal of the variable resistor is coupled to a first pin for the receiver integrated circuit and second terminal of the variable resistor is coupled to a second pin for the receiver integrated circuit; wherein the time measurements comprise a first time measurement associated with a first portion of the variable resistor between the first terminal and the variable tap node and a second time measurement associated with a second portion of the variable resistor between the second terminal and the variable tap node; wherein for the first time measurement, the receiver integrated circuit is further configured to use the first pin to apply a voltage to the first portion of the variable resistor and to use the second pin to detect a voltage change on the variable tap node; wherein for the second time measurement, the receiver integrated circuit is further configured to use the second pin to apply a voltage to the second portion of the variable resistor and to use the first pin to detect a voltage change on the variable tap node; and wherein a ratio associated with the first and second time measurements is used to determine the setting.