Method of transmitting transmission data from sensor controller to pen, and pen
A reception circuit of a pen is provided. The reception circuit includes a differential circuit that detects edges of a signal received by the pen. The reception circuit includes a ΔΣ modulation unit that uses at least two reference potentials corresponding to positive and negative values, to compare an output signal of the differential circuit and the two reference potentials and that executes feedback processing of comparison results. 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. The reception circuit includes a digital circuit that performs a correlation operation of an output signal of the ΔΣ modulation unit and known patterns to detect transmission data based on the signal.
1 . A reception circuit of a pen, the reception circuit comprising:
a differential circuit that detects edges of a signal received by the pen;
a ΔΣ modulation unit that uses at least two reference potentials corresponding to positive and negative values, to compare an output signal of the differential circuit and the two reference potentials and that executes feedback processing of comparison results, 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; and
a digital circuit that performs a correlation operation of an output signal of the ΔΣ modulation unit and known patterns to detect transmission data based on the signal.
2 . The reception circuit according to claim 1 , wherein the known patterns are chip sequences of three values.
3 . The reception circuit according to claim 1 , wherein
the 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.
4 . The reception circuit according to claim 1 , wherein
the 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.
5 . The reception circuit according to claim 1 , wherein
the differential circuit includes a variable gain amplification circuit, and
the reception circuit includes a control circuit that controls gain of the amplification circuit based on pulse density of the output signal of the ΔΣ modulation unit, by:
lowering the gain when the output signal of the ΔΣ modulation unit is fixed to +1 or −1, and
raising the gain when the output signal of the ΔΣ modulation unit is fixed to 0.