Pen for use with a touch screen
A pen for interacting with a touch screen of a computing device includes an alternating current coupling circuit and a sense-regulation circuit. The alternating current coupling circuit receives a sense signal from the touch screen. The alternating current coupling circuit transmits a transmit signal to the touch screen. The sense-regulation circuit receives the sense signal from the alternating current coupling circuit. The sense-regulation circuit receives a representation of transmit data. The sense-regulation circuit generates a comparison signal based on the sense signal and the representation of the transmit data. The sense-regulation circuit converts the representation of the transmit data into the transmit signal.
1. A pen for interacting with a touch screen, the pen comprises:
an alternating current (AC) coupling circuit comprising:
a first AC coupling circuit operable to receive a sense signal from the touch screen, wherein the first AC coupling circuit is physically located at a first location of the pen; and
a second AC coupling circuit operable to transmit a transmit signal to the touch screen, wherein the second AC coupling circuit is physically located at a second location of the pen, wherein the touch screen is capable of discerning between the first and second locations, and wherein the touch screen is capable of interpreting the transmit signal as an input to the touch screen; and
a sense-regulation circuit operable to:
receive the sense signal from the AC coupling circuit;
receive a representation of transmit data; and
convert the representation of the transmit data into the transmit signal.
2. The pen of claim 1 further comprises:
a processing circuit operable to:
receive data; and
generate the representation of the transmit data based on the data.
3. The pen of claim 2 further comprises:
a data source circuit that comprises:
a sensing element operable to:
sense a condition of the pen; and
generate a condition signal based on the sensing the condition; and
a data sense circuit operable to generate the data based on the condition signal and a reference signal.
4. The pen of claim 3 , wherein the condition comprises one or more of:
a pressure;
a tilt;
a color selection;
a mode selection;
another operational condition of the pen; and
an environmental condition.
5. The pen of claim 3 , wherein the data sense circuit comprises:
an operational amplifier operable to:
receive the condition signal on a first input;
receive the reference signal on a second input; and
generate the data based on the condition signal and the reference signal;
a regulation circuit operable to generate a regulation signal based on the data; and
a dependent supply source operable to generate an adjustment signal such that voltages on the first and second inputs remain substantially equal.
6. The pen of claim 2 , wherein the processing circuit comprises:
a processing module operable to generate digital outbound data based on the data; and
a digital to analog converter operable to generate the representation of the transmit data based on the digital outbound data.
7. The pen of claim 1 , wherein the sense-regulation circuit comprises:
an operational amplifier having:
a negative input coupled to receive the sense signal;
a positive input coupled to receive the representation of the transmit data; and
an output coupled to provide a comparison signal based on the sense signal and the representation of the transmit data;
a regulation circuit operably coupled to generate a regulation signal based on the comparison signal; and
a dependent supply source operably coupled to provide an adjustment signal to a node coupling the negative input of the operational amplifier to the AC coupling circuit, wherein the dependent supply source generates the adjustment signal based on the regulation signal.
8. The pen of claim 1 , wherein the AC coupling circuit comprises:
a conductive pen tip; and
a conductive pen shell and cone.