🐛 (touch): Touch stuck at initialization

[YannLocatelli]

Running spike lk_sensors_touch from

• mmyster/feature/lk core touch sensor #947

show 2 bugs:

1. If sensor is NOT touched at initialization, sensor stay at "Touch" value until it's really touched.
2. If sensor is touched at initialization, sensor might simply ceases to work (sometimes, not always)

Notes.

• Even with a very low sensibility, bug 1 remains.
• Actually It happens about 1 second to 2 seconds after initialization
• Reset the sensor described in datasheet (using MTPM pin) does not work

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Related issues/PR

• mmyster/feature/lk core touch sensor #947
• TouchSensorKit - Make Touch Sensor works #825

[YannLocatelli]

Other bugs of the day:

• "Touched" stuck without being touched for a limited duration sometimes
  • → Might come from to too high sensibility.
• Best value for calibration found to be lowest sensibility
  • → 2 QDAC used for left and right sensors were inversed. Fixed in d5032d5.
    Moreover, calibration process is set at start of spike, and might consider the bug of sensor stuck to "Touched" at init (see 🐛 (touch): Touch stuck at initialization #1112).

[YannLocatelli]

Update.

1. Reset MTCH101 by using MTPM pin as mentioned in datasheet does not work. Worse, it stuck the touch value to 1.
2. Once touched, the pin dedicated to sensitivity MTSA is always at the highest (~3.1V) even set to low by MCU via QDAC. High value on pin MTSA means low sensitivity.
3. Before touched, the pin dedicated to sensitivity MTSA oscillate between 0.0V and 3.1V in any case (see video).

Screen.Recording.2023-02-22.at.4.54.26.PM.mov

[YannLocatelli]

Caution - Behavior might be different on different boards.

Note.

• Channel 5 - Output QDAC
• Channel 6 - Input MTSA (Touch)
• Channel 7 - Output MTO (Touch)

Screen.Recording.2023-02-23.at.5.53.34.PM_720p.mov

Screen.Recording.2023-02-23.at.6.07.04.PM_720p.mov