Objective:
In this tutorial we will discuss how to configure and use the LPC1768 external interrupts(EINT0-EINT3).
At the end of tutorial we will see how to use the exploreembedded external interrupt library.
EINTx Pins
LPC1768 has four external interrupts EINT0-EINT3.
As LPC1768 pins are multi functional, these four interrupts are available on multiple pins.
Below table shows mapping of EINTx pins.
| Port Pin | PINSEL_FUNC_0 | PINSEL_FUNC_1 | PINSEL_FUNC_2 | PINSEL_FUNC_3 |
|---|---|---|---|---|
| P2.10 | GPIO | EINT0 | NMI | |
| P2.11 | GPIO | EINT1 | I2STX_CLK | |
| P2_12 | GPIO | EINT2 | I2STX_WS | |
| P2.13 | GPIO | EINT3 | I2STX_SDA |
EINT Registers
Below table shows the registers associated with LPC1768 external interrupts. LPC1768 interrupts can be configured as edge/level triggered.
| Register | Description |
|---|---|
| PINSELx | To configure the pins as External Interrupts |
| EXTINT | External Interrupt Flag Register contains interrupt flags for EINT0,EINT1, EINT2 & EINT3. |
| EXTMODE | External Interrupt Mode register(Level/Edge Triggered) |
| EXTPOLAR | External Interrupt Polarity(Falling/Rising Edge, Active Low/High) |
| EXTINT | ||||
| 31:4 | 3 | 2 | 1 | 0 |
| RESERVED | EINT3 | EINT2 | EINT1 | EINT0 |
EINTx: Bits will be set whenver the interrupts is detected on the particular interrupts pin.
Writing one to specific bit will clear the interrupt.