STMPE2401 datasheet(46/55 Pages) STMICROELECTRONICS

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Keypad controller

STMPE2401

46/55

13.7.1

Resistance

Maximum resistance between keypad output and keypad input, inclusive of switch

resistance, protection circuit resistance and connection, must be less than 3.2 K

Ω

13.7.2

Using the keypad controller

Before enabling the keypad controller operation, proper setup should be done by configuring

the input and output ports involved. This is achieved by programming the corresponding

GPIO control registers that determine the port direction and the necessary internal pull-up

or pull-down. For the GPIO ports that are used as keypad inputs, internal pull-up should be

enabled. For those that are used as keypad outputs, no internal pull-up or pull-down should

be enabled.

The scanning of column inputs should then be enabled for those GPIO ports that are

configured as keypad inputs by writing ‘1’s to the corresponding bits in the KPC_col register.

If any of the first three column inputs is to be used as dedicated key input, the corresponding

bits in the KPC_ctrl_msb register should be set to ‘1’. The bits in the KPC_row_msb and

KPC_row_lsb registers should also be set correctly to enable the row output scanning for

the corresponding GPIO ports programmed as keypad outputs.

The scan count and de-bounce count should also be programmed into the keypad control

registers before enabling the keypad controller operation. To enable the keypad controller

operation, the Enable_KPC bit in the system control register must be set to ‘1’ to provide the

required clock signals. The keypad controller will then start its operation by setting the

SCAN bit in the KPC_ctrl_lsb register to ‘1’.

The keypad controller operation can be disabled by setting the SCAN bit back to ‘0’. To

further reduce the power consumption, the clock signals can be cut off from the keypad

controller by setting the Enable_KPC bit to ‘0’.

ScanCount value is programmable to any value between 1-15 by writing into the scancount

N times, collecting up to 2 matrix key and 4 dedicated keys, loads the keys into 1 set of

keypad data buffer and interrupts the host system.

STMPE2401 Arkusz danych(PDF) 46 Page - STMicroelectronics