Method and system for touch sensor interface fault detection
View Patent ↗A touch sensor interface includes one or more touch detection electrodes whose capacitance increases when touched. A processor converts the increase in capacitance into a change in a counter value. A detector compares the change in the counter value with one or more count thresholds to detect faults in the touch sensor interface.
1. A system for detecting one or more faults in a touch sensor interface, the touch sensor interface comprising one or more touch detection electrodes for sensing a touch event, the system comprising:
a first oscillator, connected to at least one of the touch detection electrodes, for generating a first periodic signal based on the capacitance of the at least one touch detection electrode;
a prescaler, connected to the first oscillator, for reducing the frequency of the first periodic signal by a predetermined value to generate a second periodic signal;
a counter, connected to the prescaler, for receiving the second periodic signal and a third periodic signal, wherein the frequency of the third periodic signal is greater than the frequency of the second periodic signal, wherein the counter is updated for a count time window equal to the time period of the second periodic signal, and wherein the counter is updated for a plurality of counts based on the frequency of the third periodic signal; and
a fault and touch detector, connected to the counter, for detecting the one or more faults by calculating a difference between the plurality of counts corresponding to the count time window and a previous plurality of counts corresponding to a previous count time window and comparing the calculated difference with one or more count thresholds.
2. The fault detection system of claim 1 , further comprising at least one shared input/output (I/O) pad, connected to the at least one touch detection electrode, for receiving an input signal provided to the touch sensor interface and for transmitting an output signal to the touch sensor interface.
3. The fault detection system of claim 2 , wherein the at least one shared I/O pad receives and transmits one or more touch sensing signals from the at least one touch detection electrode to the first oscillator.
4. The fault detection system of claim 3 , further comprising at least one communication channel, connected to the at least one shared I/O pad and the first oscillator, for transmitting the one or more touch sensing signals between the at least one shared I/O pad and the first oscillator.
5. The fault detection system of claim 1 , further comprising a second oscillator, connected to the counter, for generating the third periodic signal.
6. The fault detection system of claim 5 , further comprising a programmable current source, connected to the first and second oscillators, for providing a first current to the first oscillator and a second current to the second oscillator.
7. The fault detection system of claim 1 , wherein the one or more faults comprise at least one of a PCB trace open fault, a PCB trace short fault, a touch detection electrode leakage fault, a software configuration fault, and a communication channel short fault.
8. The fault detection system of claim 7 , wherein the one or more count thresholds correspond to at least one of the PCB trace open fault, the PCB trace short fault, the touch detection electrode leakage fault, and the software configuration fault.
9. A touch sensor interface, comprising:
at least one touch detection electrode for sensing a touch event;
at least one shared input/output (I/O) pad, connected to the at least one touch detection electrode, for receiving and transmitting one or more touch sensing signals from the at least one touch detection electrode, wherein the at least one shared I/O pad receives an input signal provided to the touch sensor interface and transmits an output signal to the touch sensor interface;
at least one communication channel, connected to the at least one shared I/O pad, for receiving the one or more touch sensing signals from the at least one shared I/O pad;
a first oscillator, connected to the at least one communication channel, for generating a first periodic signal based on the capacitance of the at least one touch detection electrode;
a prescaler, connected to the first oscillator, for reducing the frequency of the first periodic signal by a predetermined value to generate a second periodic signal;
a counter, connected to the prescaler, for receiving the second periodic signal and a third periodic signal, wherein the third periodic signal is generated by a second oscillator, wherein the frequency of the third periodic signal is greater than the frequency of the second periodic signal, wherein the counter is updated for a count time window equal to the time period of the second periodic signal, and wherein the counter is updated for a plurality of counts based on the frequency of the third periodic signal;
a programmable current source, connected to the first and second oscillators, for providing a first current to the first oscillator and a second current to the second oscillator; and
a fault and touch detector, connected to the counter, for detecting the one or more faults by calculating a difference between the plurality of counts corresponding to the count time window and a previous plurality of counts corresponding to a previous count time window and comparing the calculated difference with one or more count thresholds.
10. The touch sensor interface of claim 9 , wherein each touch detection electrode comprises one or more printed circuit board (PCB) traces.
11. The touch sensor interface of claim 9 , wherein the one or more faults comprise at least one of a PCB trace open fault, a PCB trace short fault, a touch detection electrode leakage fault, a software configuration fault, and a communication channel short fault.
12. The touch sensor interface of claim 11 , wherein the one or more count thresholds correspond to at least one of the PCB trace open fault, the PCB trace short fault, the touch detection electrode leakage fault, and the software configuration fault.
13. A method for detecting one or more faults in a touch sensor interface, the touch sensor interface comprising at least one touch detection electrode for sensing a touch event, the method comprising:
generating a first periodic signal based on the capacitance of the at least one touch detection electrode;
reducing the frequency of the first periodic signal by a predetermined value to generate a second periodic signal;
updating a counter based on the second periodic signal and a third periodic signal, wherein the frequency of the third periodic signal is greater than the frequency of the second periodic signal, wherein the counter is updated for a count time window equal to the time period of the second periodic signal, wherein the counter is updated for a plurality of counts based on the frequency of the third periodic signal;
calculating a difference between the plurality of counts corresponding to the count time window and a previous plurality of counts corresponding to a previous count time window; and
comparing the calculated difference with one or more count thresholds to detect the one or more faults in the touch sensor interface.
14. The method for detecting one or more faults of claim 13 , wherein the one or more faults comprise at least one of a PCB trace open fault, a PCB trace short fault, a touch detection electrode leakage fault, a software configuration fault, and a communication channel short fault.
15. The method for detecting one or more faults of claim 14 , wherein the one or more count thresholds correspond to at least one of the PCB trace open fault, the PCB trace short fault, the touch detection electrode leakage fault, and the software configuration fault.