BU21170MUV Datasheet, PDF (21/33 Pages) Rohm – Capacitive Switch Controller IC

BU21170MUV
Calibration
Self-calibration
Self-calibration is performed by this IC automatically. It is performed in the following cases.
1. Detect drift condition :
When the IC detects the drift condition, the IC acts self-calibration. When calibration is complete, the interrupt
factor register CAL is set to ‘1’ and I/O port INT is set to ‘H’. When there is the sensor with the sensor value more
than the threshold for ‘Off to On’, IC does not detect drift condition. The interrupt factor register CAL is maskable
by the mask interrupt register CAL. The interrupt factor register CAL is cleared by writing ‘1’ to the interrupt clear
register CAL.
2. Detect noise :
When the IC detects the noise, the IC changes the scan rate to not synchronize with the noise, and the IC acts
self-calibration. When calibration is complete, the Interrupt factor register CAL is set to ‘1’ and I/O port INT is set
to ‘H’. The interrupt factor register CAL is maskable by the mask interrupt register CAL. The interrupt factor
register CAL is cleared by writing ‘1’ to the interrupt clear register CAL.
3. Detect incorrect operation :
When the finger is on the sensor at the calibration, the sensor base state is with the finger. Without the finger,
the sensor value is under the base state value. This abnormal condition is defined to incorrect operation.
Detected incorrect operation, the IC acts self-calibration. The interrupt factor register CAL is maskable by the
mask interrupt register CAL. The interrupt factor register CAL is cleared by writing ‘1’ to the interrupt clear register
CAL.
Software-calibration
Software-calibration is performed by the command from the host.
1. Write ‘1’ to the Act Software-calibration bit.
2. Finishing the calibration, the Software-calibration finish bit (CAL on Address0x10) is set to ‘1’ and I/O port INT
is set to ‘H’. For next calibration, clear the interrupt.
When the sensor setting value is changed, it is necessary to execute a soft calibration. It is necessary for
changing the value of the sensor setting that the scan is disabled.
In the act of calibration, sensor values are not changed. So the switching operations are invalid.
If the software-calibration is released at sensing sensors, IC acts calibration at next sensing sensors.
LED calibration
When the register for LED/PWM drivers operation (address area from 0xF9 to 0xFC) is written, this IC is selectable
whether to perform self-calibration. Selecting whether to perform the LED calibration is defined by the configuration
for calibration register (LEDCAL on Address 0xEF).
If there is the writing to the register for LED/PWM drivers operation (address area from 0xF9 to 0xFC), when the
finger on the sensors. Incorrect operation will be detected at the finger leaving, and so IC will act self-calibration.
Periodical calibration
The periodical calibration is to perform self-calibration periodically. This IC is selectable whether to perform
periodical calibration. Selecting whether to perform the periodical calibration is defined by the configuration for
calibration register (PERCAL on Address0xEF).
The sensor with the finger is not calibrated by the periodical calibration.
Whenever periodical calibration is complete, the interrupt factor register PERCAL is set to ‘1’ and I/O port INT is set
to ‘H’. The interrupt factor register PERCAL is maskable by the mask interrupt register PERCAL. The interrupt factor
register CAL is cleared by writing ‘1’ to the interrupt clear register PERCAL.
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TSZ22111・15・001
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TSZ02201-0L5L0F300830-1-2
14.Jul.2016 Rev.002