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STR71x GPIO SCANNING A 4x4 MATRIX KEYPAD

2 STR710 CONFIGURATION

This part is dedicated to show the STR710 Microcontroller configuration. The STR710 is used

since it offers the possibility to use external interrupts.

2.1 GPIO PORT CONFIGURATION

Rows are connected to P2.8-11 pins configured as Input Pull Up /Pull Down Weak Push-Pull

mode. For the columns, the sink transistors base pins are connected to P1.8-11 pins config-

ured as Output Push-Pull. External interrupts are triggered by a high level applied to a pin of

P2.8-11 (caused by a pressed key), they generate an interrupt on the external interrupt (XTI)

channel and can wakeup the system from STOP mode.

P1.0-7 configured as Output Push-Pull to send the value of the pressed key to the desired 7

segment display.

2.2 XTI CONFIGURATION

The External Interrupts Unit (XTI) manages 14 external interrupt lines.

In this aplication the XTI is configured to generate interrupts when a rising edge is detected on

line 2-5; any transition from low to high level on the P2.8-11 pins will trigger an external inter-

rupt.