Data sensing circuit with parallel digital filter processing
An analog to digital conversion circuit of a touch screen computing device includes a plurality of analog to digital converter circuits operable to convert a plurality of analog signals into a plurality of digital signals at an oversampling rate, a digital decimation filtering module operable to convert the plurality of digital signals into a plurality of digital filtered signals at a first output rate, a coefficient processor operable to generate real component coefficients and imaginary component coefficients of a filtering function at a plurality of frequencies, a first bandpass filter circuit operable to produce first affect values at known frequencies of the plurality of frequencies, and a second bandpass filter circuit operable to produce second affect values at selected frequencies of the plurality of frequencies.
1 . An analog to digital conversion circuit of a touch screen computing device, wherein the analog to digital conversion circuit comprises:
a plurality of analog to digital converter circuits operable to convert a plurality of analog signals into a plurality of digital signals at an oversampling rate;
a digital decimation filtering module operable to convert the plurality of digital signals into a plurality of digital filtered signals at a first output rate;
a coefficient processor operable to generate real component coefficients and imaginary component coefficients of a filtering function at a plurality of frequencies;
a first bandpass filter circuit operable to produce first affect values at known frequencies of the plurality of frequencies based on first real component coefficients and first imaginary components of the real component coefficients and imaginary component coefficients and the plurality of digital filtered signals; and
a second bandpass filter circuit operable to produce second affect values at selected frequencies of the plurality of frequencies based on second real component coefficients and second imaginary components of the real component coefficients and imaginary component coefficients and the plurality of digital filtered signals.
2 . The analog to digital conversion circuit of claim 1 , wherein the first bandpass filter circuit further comprises:
a real component circuit including:
a first multiplier operable to multiply the first real component coefficients with a digital filtered signal of the plurality of digital filtered signals to produce a first plurality of multiplication results;
a first accumulator operable to accumulate the first plurality of multiplication results until a first real component value of a first affect value of the first affect values at a known frequency of the known frequencies is produced; and
a first output buffer operable to output the first real component value; and
an imaginary component circuit including:
a second multiplier operable to multiply the first imaginary component coefficients with the digital filtered signal to produce a second plurality of multiplication results;
a second accumulator operable to accumulate the second plurality of multiplication results until an imaginary component value of the first affect value at the known frequency is produced; and
a second output buffer operable to output the first imaginary component value.
3 . The analog to digital conversion circuit of claim 1 , wherein the second bandpass filter circuit further comprises:
a real component circuit including:
a first multiplier operable to multiply the second real component coefficients with a digital filtered signal of the plurality of digital filtered signals to produce a first plurality of multiplication results;
a first accumulator operable to accumulate the first plurality of multiplication results until a first real component value of a second affect value of the second affect values at a selected frequency of the selected frequencies is produced; and
a first output buffer operable to output the second real component value; and
an imaginary component circuit including:
a second multiplier operable to multiply the second imaginary component coefficients with the digital filtered signal to produce a second plurality of multiplication results;
a second accumulator operable to accumulate the second plurality of multiplication results until a second imaginary component value of the second affect value at the selected frequency is produced; and
a second output buffer operable to output the second imaginary component value.
4 . The analog to digital conversion circuit of claim 1 , wherein the known frequencies include one or more of a self frequency and a pen frequency.
5 . The analog to digital conversion circuit of claim 1 , wherein the selected frequencies include mutual frequencies associated with regions of interest.
6 . The analog to digital conversion circuit of claim 1 further comprises:
a processing module operable to:
interpret one or more of the first affect values and the second affect values as touch data; and
output the touch data at an output rate.
7 . The analog to digital conversion circuit of claim 6 , wherein the processing module is further operable to:
select the selected frequencies.