STM32303E-EVAL board example

Firmware

The firmware used with the STM32303E-EVAL is the STM32F303_Ex01_2TKeys_EVAL and it belongs to the STM32F3xx STMTouch library. The results provided in this section are obtained with the configuration values presented in the table below.

Table 3. User configuration settings related to immunity improvements
Parameter	Configuration value
HCLK	48 MHz
TSLPRM_TKEY_DETECT_IN_TH	100
TSLPRM_TKEY_DETECT_OUT_TH	50
TSLPRM_DEBOUNCE_DETECT	2
TSLPRM_TSC_CTPH	1
TSLPRM_TSC_CTPL	1
TSLPRM_TSC_PGPSC	5
TSLPRM_TSC_USE_SS	1
TSLPRM_TSC_SSD	127

Performance

The performances of an STM32303E-EVAL board, with the configuration described above, are the following:

Acquisition performed in 1200 counts
Acquisition duration: 4.7 ms (target < 6.6 ms)

Conducted noise evaluation

The conducted noise evaluation results performed on the STM32303E-EVAL board according to IEC61000-4-6 standard is above 3 V_rms class A,

with the following test conditions:

Frequency range from 150 kHz to 80 MHz
1 % frequency steps
Dwell time 0.5 s

On worst case bandwidth, no false detection or loss is observed up to 4 V_rms, from 200 to 400 kHz with 100 Hz steps.

Conclusion

The touch sensing controller peripheral of the STM32 devices shows a high noise immunity level in compliance with IEC61000-4-6 standard (above 3 V_rms class A). These results can easily be reached by putting in practice the following recommendations:

Implement an active shield electrode and enable the active shield feature in the firmware.
Optimize the detection thresholds.
Use the debounce filter.
Use frequency hopping.
Use application filtering based on ripple, noise measurement and guard-ring or ghost detections.

Revision history

Table 4. Document revision history
Date	Revision	Changes
03-Jul-2013	1	Initial release.
11-Jun-2014	2	Added support for STM32L0 Series. Updated last bullet in Section 4.1. Proposed improvement techniques.
22-Oct-2015	3	Added support for STM32L4 Series.
14-Mar-2018	4	Updated: Figure 2. Injected signal Figure 5. Data processing Added Section1. General information.
18-Jan-2019	5	Updated: Title of the document Table 1. Applicable products
22-Oct-2019	6	Updated: Table 1. Applicable products Section 3 Section 5.1 , Section 5.2 , Section 5.5 and Section 5.6 Section 6 STM32303E-EVAL board example Added: Section 3.1 Sampling capacitor (Cs) voltage level without noise Section 3.2 Sampling capacitor (Cs) voltage level with noise Figure 9. Process flow Section 5.4 to Section 5.13
11-Aug-2021	7	Updated the Applicable products table.
10-Jan-2023	8	Updated the Table 1. Applicable products in the Section Introduction to incorporate the STM32WBA series. Updated the whole document with minor changes.
06-Mar-2024	9	Added STM32U0 series Updated document title
06-Dec-2024	10	Added STM32U3 series