I have set a pin on a Cortex M3 to act as an rising-edge triggered interrupt and it's not firing for some reason. What it should do is receive a 1Hz pulse, trigger an interrupt and start a 12.8Khz square wave.
__main and EINT3_IRQHandler are defined in startup code created by the program, Keil uVision 5. The GPIO interrupts share the EINT3 interrupt vector with a different external interrupt. I figured it would only be a matter of activating the GPIO and EINT3 interrupts then putting the handler within the EINT3_IRQHandler label.
The GPIO interrupts are described on page 129 of this data sheet.
http://www.nxp.com/documents/user_manual/UM10360.pdf
I also tried to just set it to read the interrupt status by using
check
CMP [status_register], #1 ; Check interrupt status
BEQ wave_gen ; If triggered, start square wave
BNE check ; else keep checking
and use that as a trigger but that didn't work either.
This is my code.
AREA main, CODE, READONLY
EXPORT __main
EXPORT EINT3_IRQHandler
ALIGN
__main
LDR R1,=0x2009c000 ; Pointer to base of port 0
LDR R2,=0x00000001 ; To control pin 0 for square wave
LDR R3,=0x00000001 ; For XOR to invert pin 0
STR R2,[R1,#0x00] ; Set pin 0 to output mode (base+0x00)
STR R2,[R1,#0x14] ; Pin 0 HIGH
LDR R4,=780 ; Set up timer
LDR R5,=0x40028080 ; GPIO Rising Edge Interrupt
LDR R7,=0xE000E100 ; Set EINT3-enable register
LDR R6,=0x00000002 ; For pin 0:1
STR R6,[R5,#10] ; Activate 0:1 as rising edge interrupt
LDR R6,=0x00200000 ; To enable ENINT3
STR R6,[R7] ; Enables EINT3
WFI
wave_gen
SUB R4, #1 ; Decrement timer
CMP R4, #0 ; Compare to 0
BNE wave_gen ; If !0, keep looping
LDR R4,=975 ; Reset timer
EOR R2,R3 ; Invert bits
STR R2,[R1,#0x14] ; Invert pin
MUL R3,R3,R3 ; To waste cycles, ignore (1*1=1)
MUL R3,R3,R3
B wave_gen ; Restart loop
EINT3_IRQHandler
B wave_gen ; Start square wave
ALIGN
