Method of transmitting transmission data from sensor controller to pen, and pen
[Object] To allow a pen to properly receive an uplink signal even if there is dullness in a waveform of the uplink signal. [Solution] Provided is an invention of a method of transmitting transmission data from a sensor controller 31 that detects a pen 2 to a pen through a sensor electrode group 30 . The pen 2 includes a pen tip electrode arranged near a pen tip, an analog circuit that detects edges of a signal led to the pen tip electrode, and a digital circuit that performs a correlation operation of an output signal of the analog circuit and known patterns to detect transmission data. The sensor controller 31 generates a pulse signal representing the transmission data and transmits the pulse signal, by using a main signal and a sub signal of the pulse signal so as to enhance the edges, thereby transmitting the transmission data through the sensor electrode group.
1. A pen that receives transmission data transmitted through a sensor electrode group by a sensor controller that detects the pen, the pen comprising:
a pen tip electrode arranged near a pen tip;
a differential circuit that detects edges of a signal led to the pen tip electrode;
a ΔΣ modulation unit that uses two reference potentials corresponding to at least positive and negative values, respectively, to compare an output signal of the differential circuit and the two reference potentials and that executes feedback processing of comparison results; and
a digital circuit that performs a correlation operation of an output signal of the ΔΣ modulation unit and known patterns to detect the transmission data.
2. The pen according to claim 1 , wherein the known patterns are chip sequences of three values.
3. The pen according to claim 2 , wherein the ΔΣ modulation unit uses two or more first comparators corresponding to positive values and two or more second comparators corresponding to negative values to execute folding modulation.
4. The pen according to claim 3 , wherein
an output signal of the ΔΣ modulation unit is a pulse signal of three values, and
the digital circuit performs a correlation operation of the pulse signal of three values and the chip sequences of three values to detect the transmission data.
5. The pen according to claim 3 , wherein
an output signal of the ΔΣ modulation unit is a pulse signal of five values, and
the digital circuit performs a correlation operation of the pulse signal of five values and the chip sequences of three values to detect the transmission data.
6. The pen according to claim 1 , wherein
the differential circuit includes a variable gain amplification circuit, and
the pen further includes a control circuit that controls gain of the amplification circuit based on pulse density of the output signal of the ΔΣ modulation unit.