QST108 STMicroelectronics, QST108 Datasheet - Page 19

• Manufacturer Part Number: QST108
• Description: Capacitive Touch Sensor Device 8 Keys With Individual Key State Outputs Or I2c Interface
• Manufacturer: STMicroelectronics

QST108
4.6.2
4.6.3
4.6.4
General-purpose outputs
I
in output push pull mode 0 by default. Their state can be changed using the
SET_GPIO_STATE I
Figure 5.
IRQ pin
The IRQ pin is an open drain output with an internal pull-up. It can be used to inform the
Master device about any change in the key status. The IRQ line is pulled low every time the
state of any of the enabled keys changes. This includes any change in the touch state of the
key, a faulty key or a new calibration of one or more keys. The reported changes may then
be accessed by the Master device by using the GET_KEY_STATE command.
To improve communication response time, this signal suspends Low Power mode until the
Master device has issued a communication with the QST device.
Communication packet
The communication between the Master device and the QST108 (Slave) consists of two
standard I
The first frame is sent by the Master device using the QST108 device address with the write
bit set. The data bytes consist of the command byte which is eventually followed by the
parameters and a checksum byte.
The second one is sent by the Master device using the QST108 device address with the
write bit reset. The QST108 completes the frame with data according to the command
previously sent by the Master device. The device finishes the frame by sending a checksum
byte for communication integrity verification.
If the read frame is omitted, the command may not be taken into account.
To initiate the communicate with the QST108, the Master device must send the
GET_DEVICE_INFO command in order to unlock access to all the other commands.
2
C mode allows to drive up to 5 general-purpose outputs. These output pins are configured
2
C frames.
Optional LED schematic
2
C command.
GPO
n
V
UNREG
R
Device operating modes
C (10 nF)
Ai12570
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