3.4 Easy Tune
The Easy Tune option saves development time and board space by setting the button sensitivity automatically. During the run-time, the sensitivity is further adjusted based on the observed noise level, ensuring operations under changing noise environments. The Easy Tune feature is an alternative to classic sensitivity tuning (as provided via CFG2) and is intended for use on regular buttons for a predefined sensor size and overlay thickness. Refer to Section 3.4.1 - CFG2 Configuration with Easy Tune Enabled for further details.
| Input on Easy Tune Pin | Feature |
|---|---|
| 0V | Easy Tune feature is enabled |
| VDD | Easy Tune feature is disabled |
The Easy Tune feature controls the sensitivity and oversampling settings. Easy Tune applies the settings required to satisfy the basic touch tuning recommendation as provided in the Guide to Tuning Touch Sensors. With increased sensitivity, increasing the oversampling is recommended to maintain noise robustness. If the user doesn’t change the oversampling accordingly, Easy Tune automatically adjusts to the recommended settings for robust operation. Either the minimum amount of recommended oversampling is applied or, if higher, select the user setting according to CFG2.
Consequently, the number of components is reduced by connecting CFG1 to 0V if enabling Easy Tune. Refer to Section 3.4.2 - CFG1 Configuration with Easy Tune Enabled for further details.
CFG2 Configuration with Easy Tune Enabled
When Easy Tune is enabled, the CFG2 and CFG1 configurations are re-mapped to avoid the necessity for resistor dividers (reducing BOM and required board space). Table 3-8 provides the recommended configuration for sensor size and overlay thicknesses.
| Button Size | Overlay Thickness | CFG2 | CFG1 |
|---|---|---|---|
| 10~12 mm diameter | 1~2 mm | 0 | 0 |
| 10~12 mm diameter | 2~4 mm | VDD | 0 |
The Easy Tune feature can be adjusted, if needed (e.g., for usage outside the standard button sizes or other overlay thicknesses). The user may change the CFG2 and CFG1 configuration to adjust the sensitivity and oversampling.
| CFG2 Configuration* | Sensitivity |
|---|---|
| 0 | As per recommended sensor configuration |
| 0-191 | Linear Increase in sensitivity |
| 192-250 | Invalid Range |
| 251~255 | As per recommended sensor configuration |
| *Sensitivity value varies linearly from 0 to 255 based on the voltage applied on the CFG2 pin - 0 corresponds to GND and 255 corresponds to VDD. | |
When the Easy Tune feature is enabled, the thresholds are adjusted automatically based on the noise level on the touch sensors. Easy Tune comes with two standard settings (accessible by connecting CFG2 to either GND or VDD) which enable the out-of-the-box Easy Tune usage for buttons of regular size and overlay thickness (see Table 3-8).
If needed, the range of variation on Easy Tune can be controlled using the CFG2 option. The variation in threshold is adjusted based on noise ranging ±50% of the threshold configured using the CFG2 option.
For instance, if the CFG2 option sets the threshold to 50, the touch delta on the given sensor will be nearly 100 counts. For this configuration, the Easy Tune feature can vary the threshold run-time between 25 and 75. Under no noise, the threshold value is set to 25. As noise levels increase, the Easy Tune feature increases the threshold in steps of ten counts for a maximum value of 75. As noise levels recede, the threshold values are reduced in five count steps.
Use the CFG2 setting to scale touch delta, if needed. The Easy Tune maximum and minimum threshold levels must be around 75% and 25% levels of observed touch delta.
CFG1 Configuration with Easy Tune Enabled
Table 3-10 shows the minimum recommended oversampling value when the Easy Tune option is enabled.
| CFG2 Configuration * | Description | Minimum Recommended Oversampling |
|---|---|---|
| 0 | Standard Button Type A | 16 |
| 64-127 | Adjusted Easy Tune | 32 |
| 128-191 | Adjusted Easy Tune | 64 |
| 192-250 | Invalid | Invalid |
| 255 | Standard Button Type B | 32 |
| *Sensitivity value varies linearly from 0 to 255 based on the voltage applied on the CFG2 pin – 0 corresponds to GND and 255 corresponds to VDD. | ||
With Easy Tune enabled:
- If the user-configured CFG1 value is greater than or equal to the minimum recommended value, then the user configured value will be used.
- If the user configured CFG1 value is less than the minimum recommended value oversampling, then the user configuration will be overwritten and the recommended minimum oversampling is used.
As the recommended minimum oversampling is applied automatically, Easy Tune removes the need to select oversampling. Connecting CFG1 to GND is sufficient to ensure operation, removing the need for a resistor ladder and reducing BOM and board space. Connecting CFG1 to a pin other than GND enables the user to enforce an oversampling higher than recommended (see Table 3-11).
| CFG1 Configuration | Minimum Recommended Oversampling |
|---|---|
| A | Minimum recommended oversampling will be automatically applied |
| B | Always x64 oversampling will be applied |
| C | Minimum recommended or x32 oversampling will be applied, whichever is higher |
| D | Minimum recommended or x16 oversampling will be applied, whichever is higher |
For example, if CFG2 is configured to VDD (2–4 mm overlay above a 10–12 mm diameter button), then the recommended oversampling value is 32. A resistor ladder is needed to set x32 oversampling on CFG1. With Easy Tune enabled, the MTCH1030 will follow that guidance automatically so that CFG1 can be connected to GND. The MTCH1030 will use the recommended minimum oversampling of 32.