STEVAL-ICB002V1 STMicroelectronics, STEVAL-ICB002V1 Datasheet - Page 9

• Manufacturer Part Number: STEVAL-ICB002V1
• Description: BOARD EVAL TOUCH STM32/STMPE821
• Manufacturer: STMicroelectronics

Specifications of STEVAL-ICB002V1

• Sensor Type: Touch, Capacitive
• Sensing Range: 3 Button/Key
• Interface: USB
• Voltage - Supply: 3.3V
• Embedded: Yes, MCU, 32-Bit
• Utilized Ic / Part: STMPE821
• Silicon Manufacturer: STMicroelectronics
• Kit Contents: Board
• Features: PWM/GPIO Output, Multiple Touch Detection, Demonstrates Up To 3 Capacitive Touch Keys
• Svhc: No SVHC (15-Dec-2010)
• For Use With: 497-10173 - BOARD EVAL S-TOUCH STM32
• Lead Free Status / RoHS Status: Lead free by exemption / RoHS compliant by exemption
• Sensitivity: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 497-10167

STMPE821
1.4.1
1.4.2
Noise filtering
When the STMPE821 is operating in the vicinity of highly emissive circuits (DC-DC
converter, PWM controller/drive etc), the sensor inputs will be affected by high-frequency
noise. In this situation, the time-integrating function could be used to distinguish between
real touch, or emission-related false touch.
The INTEGRATION TIME and STRENGTH THRES registers are used to configure the time-
integrating function of STMPE821.
Data filtering
The output from the calibration unit is an instantaneous "TOUCH" or "NO TOUCH" status.
This output is directed to the filtering stage where the TOUCH is integrated across a
programmable period of time. The output of the integration stage would be a "STRENGTH"
(in STRENGTH register) that indicates the number of times a "TOUCH" is seen, across the
integration period.
The "STRENGTH" is then compared with the value in "STRENGTH THRESHOLD" register.
If STRENGTH exceeds the STRENGTH THRESHOLD, this is considered a final, filtered
TOUCH status.
In data filtering stage, 3 modes of operation is supported:
Mode 1: Only the “touch” channel with highest STRENGTH is taken
Mode 2: All the “touch” channels with STRENGTH > STRENGTH THRESHOLD is taken
Mode 3: The 2 “touch” channel with the highest STRENGTH is taken. These modes are
selected using the FEATURE SELECTOR register.
The final, filtered data is accessible through the Touch Byte register.
Doc ID 14478 Rev 5
STMPE821 functional overview
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