I have a problem getting a UART0 receive interrupt to function using Eclipse. I cannot get the ISR for UART0 to respond to an interrupt request. It appears the request is enabled and acknowledged, but not processed. I suspect the problem is with the crt0.s assembler startup code. Unfortunately, I don't really know a lot about what needs to be there in terms of interrupt handlers. I've attached a copy of the crt0.s file, along with a snippet showing the interrupt initialization routine and the UART0 ISR (barebones - just sends back a "u" to indicate the routine has been serviced and clears the interrupt). Here are the values of the status registers before I hit a key to send a character to UART0: VICIRQStatus = 0x0 VICFIQStatus = 0x0 VICIntSelect = 0x0 VICIntEnable = 0x40 VICSoftInt = 0x0 VICDefVectAddr = 0x494 VICVectAddr0 = 0x3A0 VICVectCntl0 = 0x26 VICVectAddr1 = 0x374 VICVectCntl1 = 0x27 U0IER = 0x1 U1IER = 0x0 And here are the status registers after I hit the key to send a character to UART0 VICIRQStatus = 0x40 VICFIQStatus = 0x0 VICIntSelect = 0x0 VICIntEnable = 0x40 VICSoftInt = 0x0 VICDefVectAddr = 0x494 VICVectAddr0 = 0x3A0 VICVectCntl0 = 0x26 VICVectAddr1 = 0x374 VICVectCntl1 = 0x27 U0IER = 0x1 U1IER = 0x0 As you can see, the VICIRQStatus changed, but the interrupt never vectored to the service routine. Does there need to be a low-level assembler handler in the crt0.s code, or am I doing something wrong in the high-level code? Thanks for any help in this matter!
Update: I was able to branch to the interrupt service routine by changing the following code in crt0.s: msr CPSR_c,#MODE_SYS|I_BIT|F_BIT // System Mode changed to: msr CPSR_c,#MODE_USR // User Mode Now it branches to the service routine and hangs up, so I suspect I am now in the infinite loop handler, and need to figure out how to write an interrupt handler in assembler...
Update:
Okay, I think I've figured out the problem:
I changed the interrupt declaration from:
void UART0_irq (void)
to:
void _attribute_ ((interrupt("IRQ"))) UART0_irq(void)
All appears to be working now.
I would still appreciate any comments to educate me further on this
matter.
Thanks!
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