STMPE2403 datasheet(47/63 Pages) STMICROELECTRONICS

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STMPE2403

Keypad controller

47/63

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 during each scanning cycle. While one row is

driven 'LOW', all other rows are in tri-state and pulled up. 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.

12.1

Keypad configurations

The keypad controller supports the following types of keys

–

Up to 8 Input *12 Output Matrix Keys

–

Up to 8 Special Function Keys

–

Up to 4 Dedicated Keys

Figure 9.

Maximum configuration

STMPE2403

Matrix Keypad

(8*12)

Input 0-7

Special Function Keys

8*12 (96) Matrix Keys

8 Special Function Keys

0 Dedicated Keys

STMPE2403 Datasheet(PDF) 47 Page - STMicroelectronics