SYS/BIOS and SCI interrupt for TMS320F28335.

In fact, you can add a wrapper for your HWI. and then initilize this function pointer before BIOS start.

Ok, I'm making progress but the engineer in me wants the implementation to work a particular way.  I want to set the arg parameter in the Hwi_Params struct equal to the pointer value of the class instance that is handling the SCI like this (it's just a code snippet, not the full thing)

class SCI_A : public SCI
{
protected:
    Void hw_init(Uint32 SysClk);
    Void start_tx_pump(Void);
    bool isr_init(void);
public:
    SCI_A(Uint32 SysClk, Uint32 baud, Uint16 data_bits, Parity parity, Stop_Bits stop_bits, Mode mode);
    ~SCI_A();
}

bool SCI_A::isr_init(Void)
{
    // The SCITXINTA is interrupt INT9.2 This maps to interrupt ID 97
    // The SCIRXINTA is interrupt INT9.1 This maps to interrupt ID 96
    bool result = true;
    Hwi_Params hwiParams;
    Error_Block eb;
    Error_init(&eb);
    Hwi_Params_init(&hwiParams);
    hwiParams.arg = (xdc_UArg) self;
    hwi0 = Hwi_create(97, SCITXAFunc, &hwiParams, &eb);
    if (hwi0 == NULL) {
        System_abort("Hwi create failed");
        result = false;
    }
    return (result);
};

With this implementation I can cast the parameter passed to the ISR as an instance of the SCI_A class and use this pointer to get the data out of the SCI FIFO.  This would be part of a larger framework where applications would have an instance of the SCI and not have to worry about the low level details of the ISRs, configuration, or FIFO. 

My problem is that the xdc_UArg parameter is only 16 bits wide but the memory map for the TMS32f28335 can be upto 22 bits wide and I have no guarantee that the linker will put the isr and the object within 64k of each other.  What I need to do is pass a 32 bit value to the ISR to guarantee  the cast will work correctly.   I'm trying to avoid using a global SCI_A pointer that gets used by the ISR, but to me it looks like I will not have a choice.

Any advice would be greatly appreciated.

Hi Andrew,

UArg can hold a pointer.

From the following website: http://rtsc.eclipse.org/cdoc-tip/xdc/package.html#xdoc-sect-3

UArg

this unsigned integer type is large enough to hold a Fxn, Ptr, or Int.

Todd

Hi Todd,

Thanks for the reply but the problem is that it is an unsigned integer type.

From the TMS320C28x Optimizing C/C++ Compiler v6.1 Section 6.4 Data Types (Pg 87)

Type                      Size              Representation                Minimum         Maximum

unsigned int          16 bits           Binary                              0                      65535

This indicates that the UArg type ( which is a unsigned int) can only hold a pointer to a function that resides in the lower 16 bits of the address space. What happens if my interrupt function is a far pointer away from the heap instance of a dynamically created c++ object?

But UArg is not an "Int". It can hold either an "Int" or a pointer. I run the following code on a C28_float device

System_printf("sizeof(UArg)   = %d\n", (Int)sizeof(UArg));
System_printf("sizeof(Int)    = %d\n", (Int)sizeof(Int));
System_printf("sizeof(Void *) = %d\n", (Int)sizeof(Void *));

And the output was as follows:

sizeof(UArg)   = 2
sizeof(Int)    = 1
sizeof(Void *) = 2

Todd

Thanks Todd,

This is great news.  I got tripped up by the documentation.  Where is UArg defined?