Features

mTouch Framework Implementation Features

We focused on creating a system that exhibits high signal sensitivity and noise immunity. To achieve these goals, we implemented the following features:

• Basic mTouch Sensor Configuration is fast and simple
• Built-in support for:
  • Proximity Sensors provide a higher level of signal-to-noise ratio by implementing an additional median filter
  • Sliders and Wheels decoding based on the relationship between sensor shift percentages
  • Matrix Designs support to help guarantee the reliability of 'node' press decisions
  • Most-Pressed Algorithm to limit the number of simultaneous 'pressed' sensors in high-crosstalk systems
  • Scanning Modes to support applications with multiple states and a desire to scan different sensors in each state
  • Guard Ring / Shield traces to actively reduce parasitic capacitance and increase sensitivity
  • Mutual Coupling Drives to scan for changes in the relative permitivity, or coupling, near the sensor
• Detailed warning and error messages guide the user in case of an incorrect configuration value

- Acquisition Module

• Differential CVD scanning method drastically attenuates low frequency noise (Including 50/60Hz, up to low KHz)
• Sample rate jittering algorithm eliminates issues with resonant noise frequencies
• Generated assembly implementation maximizes noise immunity and minimizes execution time
• Ability to force the scan sequence to use the DAC as the reference voltage to the ADC's hold capacitor.

- Filtering Module

• Decimate-filtered result register seeding an accumulator array provides impulse noise rejection and an increase in signal through oversampling
• Baseline average tracks environmental changes to maximize response time
• Enhanced filtering options allow for customizable filter behavior and update speed based on the application's requirements
• Median filter implemented for proximity sensors to further increase the SNR

- Decoding Module

• Individual thresholds provide the ability to adjust for different sensor sizes and types
• Threshold hysteresis reduces sensor flickering in noisy conditions as well as increasing the reliability of sensor state transitions
• Configurable press timer to implement a maximum press duration for the application
• Debounce counters provided to further increase reliability, if desired.
• Most Pressed Algorithm is implemented automatically for matrix applications on the rows and columns, separately.
• Toggle mode provided to quickly and efficiently implement a change-on-press-only button output behavior.

- Communication

• Preconfigured software or hardware UART implementation to report ASCII data one-way to a COM port
• UART, I2C, and SPI two-way communication protocol to read/write configuration and RAM values at run-time
• Store configuration values in EEPROM for run-time editing capability