STMPE2401 datasheet(41/55 Pages) STMICROELECTRONICS

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STMPE2401

Keypad controller

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The keypad column inputs enabled by the KPC_col register are normally ‘HIGH’, with the

corresponding input pins pulled up by resistors internally. After reset, all the keypad row

outputs enabled by the KPC_row register are driven ‘LOW’. If a key is pressed, its

corresponding column input will become ‘LOW’ after making contact with the ‘LOW’ voltage

on its corresponding row output.

Once the key scan controller senses a ‘LOW’ input on any of the column inputs, the

scanning cycles will then start to determine the exact key that has been pressed. The twelve

row outputs will be driven ‘LOW’ one by one (if the row output is enabled) during each

scanning cycle. While one row is driven ‘LOW’, the other rows are driven ‘HIGH’. (The pull-

ups and pull-downs of row outputs are always disabled). If there is any column input sensed

as ‘LOW’ when a row is driven ‘LOW’, the key scan controller will then decode the key

coordinates (its corresponding row number and column number), save the key data into a

de-bounce buffer if available, confirm if it is a valid key press after de-bouncing, and update

the key data into output data FIFO if valid.

13.1

Registers in keypad controller

Table 37. Register in keypad controller

Address

Description

Auto-Increment

(during sequential

R/W)

0x60

KPC_col

Keypad column scanning register

Yes

0x61

KPC_row_msb

Keypad row scanning register

Yes

0x62

KPC_row_lsb

Yes

0x63

KPC_ctrl_msb

Keypad control register

Yes

0x64

KPC_ctrl_lsb

Yes

0x68

KPC_data_byte0

Keypad data register

0x69

KPC_data_byte1

0x6A

KPC_data_byte2

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