I'm using a PGA970 with a ARM Cortex M0 and I'm struggling with the basic function of its SysTick interrupt. My current state is this:
void main(void) { Interrupt_Config(); __set_PRIMASK(0); //Enables Interrupts SYST_Config(0x0000004F,0x00000007); //configures Reload value + enables counting while(1) {} //stay in main and wait for Interrupt }
with this definition:
void Interrupt_Config(void) { /* Clear interrupt pending register */ NVIC_UNPEND0 = 0xFFFFFFFF; /* Set priority of NVIC interrupt */ NVIC_PRI0 = 0x80400000; NVIC_PRI1 = 0xC0C0C0C0; /* * Enable NVIC interrupts * NVIC interrupt for external interrupt 1 i.e. TADC is disabled */ NVIC_ENABLE0 = 0xFFFFFFFD; }
According to Ti priority of SysTick is set to -1 with the highest priority being -3 (used by fault handlers). Custom interrupts start with the priority of 1.
SysTick M0 System Timer SysTick Registers:
These are my SysTick registers. The CSR register is enabled by setting the value of 7. When the Current Value Register hits 0 it gets reset to the Reload Value which is defined in the RVR. When this reload happens the Countflag-Bit in the CSR is set to 1. Everything of this is working as described in my case.
After the Countflag-Bit is set, an interrupt should be triggered executing the Syst_Handler as shown below. Since I'm using it as a basic counter for now I can confirm that it never gets called.
int SYSTcounter=0; interrupt void SYST_Handler(void) { SYSTcounter++; }
Now to the weird part. The NVIC_INT_CTRL register was renamed by Ti and represents the ISCR of ARM. After executing the Code and waiting for the Countflag it has a Value of 0x67108867. The SysTick exception has a value of 15 --> 1111 which can be seen in VECACTIVE in the picture below. BUT the VECPENDING remains empty same for ISRPENDING. ISCR values and explanation of Bits
As far as my understanding goes something most probably some stupid setting I forgot prevents my Systick from being executed although it realises that it should be executed. My interrupts in general are working as an unexpected power loss triggers the FaultHandler on the next startup as desired.
Aditionnaly this is my vector table on which you can see SYST_Handler goes by exception number 15. So far I didn't manage to get any Interrupt going, except for the IntDefaultHandler which states that it gets excecuted whenever the processor recieves an unexpected interrupt. I did that by cutting the power supply off and immediatly reconnecting it. All of them should be enabled and working since interrupts in general should be enabled for IntDefaultHandler to work.
#pragma DATA_SECTION(g_pfnVectors, ".intvecs") void (* const g_pfnVectors[])(void) = { (void (*)(void))((unsigned long)&__STACK_TOP), // The initial stack pointer ResetISR, // The reset handler NmiSR, // The NMI handler FaultISR, // The hard fault handler IntDefaultHandler, // The MPU fault handler IntDefaultHandler, // The bus fault handler IntDefaultHandler, // The usage fault handler 0, // Reserved 0, // Reserved 0, // Reserved 0, // Reserved IntDefaultHandler, // SVCall handler IntDefaultHandler, // Debug monitor handler 0, // Reserved IntDefaultHandler, // The PendSV handler #if (SYST_TESTING == 1) SYST_Handler, // The M0 System timer handler #else IntDefaultHandler, // The M0 System timer handler #endif ADC_Handler, // ADC handler IntDefaultHandler, #if(OWI_TESTING == 1) // OWI_Activation_Handler, // OWI_Activation_Handler, OWI Activation handler #else IntDefaultHandler, #endif #if (COMBUF_TESTING == 1) COMBUF_Handler, // COMBUF RX handler #else IntDefaultHandler, // #endif IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // IntDefaultHandler, // };
Anybody got any Ideas?
> But I cant find any Information on what to write into such registers.
A lot of vendors choose not to document the ARM "Core" functions. Instead they just refer you to the ARM documentation.
See here, and related: https://developer.arm.com/documentation/dui0497/a/cortex-m0-peripherals/system-control-block/system-handler-priority-registers
(and also (pdf warning) https://documentation-service.arm.com/static/5f8ff05ef86e16515cdbf826 )
You're using TI's CCStudio and CCS? I tried making a sample PGA970 program, and I couldn't even find arm_m0.h, nor the NVIC_PRI0 symbol you are using :-(
NVIC_PRI0 symbol you are using :-(
This is when a standard like CMSIS comes in handy; in theory the functions and register names for the ARM core and core peripherals would all be the same, regardless of who put the vendor-dependent stuff in, and regardless of which compiler or IDE you are using. (At least for CMSIS-Core, which defines such things for the ARM core. Parts like CMSIS-Driver that attempt to abstract higher-level peripherals like UARTs and Ethernet are ... more ambiguous in their utility (because of the vast differences in hardware implementations.)) (Although even CMSIS Core doesn't seem to be perfect. The SHPR3 register that I think is relevant (and documented in the Archiecture Refrence Manual) seems to be called SCB->SHP[1] in the core_cm0.h file.)