AN4312 · Application noteHow to design surface sensors for touch sensing applications on STM32 MCUs
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Conclusion

Conclusion

The layout and design of capacitive sensing boards usually present conflicts between all signals present on the application. This document presents general guideline for resolving all issues. When the recommendations cannot be followed, tests must be performed to validate the implementation and verify the sensitivity and robustness of the impacted channel.

To summarize, the layout of a touch sensing application must reduce the ground coupling to a minimum and use short clean wires as far as possible from other potential interference sources.

Revision history

Table 4. Document revision history
DateVersionChanges
30-Sept-20131Initial release.
02-Nov-20162Updated:
  • Table 1: Applicable products
  • Figure 8: Examples of cases where a LED bypass capacitor is required
  • Figure 9: TC I/O
  • Figure 10: FT I/O
  • Figure 11: Typical power supply schematic

Added Section 2.4: TC versus FT I/O.

28-Jun-20173Updated Section 2.4: TC versus FT I/O.
30-Aug-20184Specific note added in Section 3.3: Linear sensor and Section 3.4: Rotary sensor.
23-Jan-20195Updated:
  • Title of the document
  • Table 1. Applicable products
7-May-20216Added:
  • STM32L4+ and STM32L5 Series in Table 1
  • Figure 9. Avoid to swap resistor and LED
Updated:
  • Figure 8. Examples of cases where a LED bypass capacitor is required
  • Section 2.4 TC versus FT and TT I/Os
10-Aug-20217Updated the Applicable products table.
10-Jan-20238Updated the Table 1. Applicable products in the Introduction to incorporate the STM32WBA series.

Updated the document with minor changes.

06-Mar-20249Added STM32U0 series

Updated document title

18-Dec-202410Updated document scope to include STM32U3 series.