Thanks Mark,
That cleared it up even further...
I realized the problem in the original 16byte structure that I posted...
I assumed that the top of the structure is the MSB... but it's actually the
LSB... but i was filling it in the right way...i was filling in the MSB in
buff[0] and LSB in buff[15]... buff[15] being the highest location in mem,
which is bottom of structure...
all the bytes were ordered correctly... but I think the bits werent becuase i
was recieving bits from serial input...MSB first... but the MSP430 is little
endian... thus LSB is first!!
the final fix was to ... Re-arrange the definitions of the structure.. flip
everything... (the MSB become LSB and so on)... and fill it up with the
right order..and that works! :)
buff[15] = MSB..
.......
buff[0] = LSB
I allways fall for those Endian problems...
thanks for help,
Abe..
On November 20, 2003 11:33 am, Stokes, Mark wrote:
> Actually, it hasn't swapped nibbles, it has swapped bytes. But more
> accurately, you have swapped bytes.
> When you declare:
> nibble.buffb[0]=0x12;
> nibble.buffb[1]=0x34;
> You are declaring them backwards.
> The output is accurate:
> nibble1 2
> nibble2 1
> nibble3 4
> nibble4 3
> Mem location Zero is the first one, and mem location one is the second.
> The output is exactly the same as the second example except w/ the bytes
> reversed. As you have the union laid out, you have nibbles 1 and 2
> corresponding to buffb[1], and 3 and 4 corresponding to buffb[0]. Which is
> correct. In looking at the documentation on struct, it's not totally
> obvious that the elements are actually allocated in reverse order. For
> instance, in your case, the first mem location is nibble4, then nibble3,
> and so on. With this knowledge, it is obvious that the declaration is
> correct. The only way I was able to surmise this was by looking at the
> struct section of my C++ book. It references the function biosequipt( )
> which returns an int that contains a bunch of useful bits. The
> documentation for that function in my Borland Compiler gave this:
> Return Value:
> The return value is interpreted as a collection of bit-sized fields.
>
> +------------------- Number of parallel printers installed:
> | 00 = 0; 01 = 1; 10 = 2; 11 = 3
> | +--------------- Serial printer attached
> |
> | | +------------ Game I/O attached
> | |
> | | | +------ Number of COM ports: 000 = 0, 001 = 1,..., 111 =
> | | | 7
> | | |
> | | | | + Direct memory access (DMA)
> | | | |
> | | | | | 0 = Machine has DMA; 1 = Machine doesn't have
> | | | | | DMA
>
> +-----+--+--+--------+--+-----------------------+
>
> |15|14|13|12|11|10| 9| 8| 7| 6| 5| 4| 3| 2| 1| 0|
>
> +-----------------------+-----+-----+-----+--+--+
> Number of disk drives: ---+ | | | |
> 00 = 0; 01 = 1; 10 = 2; 11 = 3 | | | |
> Initial video mode -------------+ | | |
> 00 = Unused | | |
> 01 = 40x25 BW with color card | | |
> 10 = 80x25 BW with color card | | |
> 11 = 80x25 BW with mono card | | |
> Motherboard RAM size -----------------+ | |
> 00 = 16K; 01 = 32K; 10 = 48K; 11 = 64K | |
> Floating-point coprocessor ----------------+ |
> Boot from disk -------------------------------+
>
> (obviously quite an outdated function)
>
> And the struct that accesses that is declared as:
> struct equipment {
> unsigned hasdiskette : 1;
> unsigned hascoprocessor: 1;
> unsigned planar : 2;
> unsigned videomode : 2;
> unsigned numfloppy : 2;
> unsigned hasdma: 1;
> unsigned numserial : 3;
> unsigned gameadaptor : 1;
> unsigned serialprinter: 1;
> unsigned numprinters : 2;
> };
>
> union twotypes {
> struct equipment eq; /* The bit field structure */
> int k; /* Same bytes as an integer */
> };
>
> Hope this cleares it up.
> -Mark Stokes
>
>
>
> -----Original Message-----
> From: Ibrahim Saidi [mailto:[email protected]]
> Sent: Thursday, November 20, 2003 5:46 AM
> To: [email protected]
> Subject: Re: [Mspgcc-users] [Fwd: Structure help]
>
>
>
> Hi,
> refrence to the problem.....
> I compiled the following code on just a regular GNU gcc compiler... (for my
> pentium machine target, not the msp430)
>
> see the output below:
>
>
> union nibble_t {
>
> struct nibbles {
> unsigned nibble1:4;
> unsigned nibble2:4;
> unsigned nibble3:4;
> unsigned nibble4:4;
> };
> unsigned char buffb[2];
> unsigned buff;
> };
>
> int main(void)
> {
> int i;
> union nibble_t nibble;
>
> nibble.buffb[0]=0x12;
> nibble.buffb[1]=0x34;
> printf("\n2 bytes\n");
> printf("nibble1 %x \n",nibble.nibble1);
> printf("nibble2 %x \n",nibble.nibble2);
> printf("nibble3 %x \n",nibble.nibble3);
> printf("nibble4 %x \n",nibble.nibble4);
>
> printf("\none word\n");
> nibble.buff=0x1234;
> printf("nibble1 %x \n",nibble.nibble1);
> printf("nibble2 %x \n",nibble.nibble2);
> printf("nibble3 %x \n",nibble.nibble3);
> printf("nibble4 %x \n",nibble.nibble4);
>
> return 0;
> }
>
>
> ------------------------------- OUTPUT-----------------------
> 2 bytes
> nibble1 2
> nibble2 1
> nibble3 4
> nibble4 3
>
> one word
> nibble1 4
> nibble2 3
> nibble3 2
> nibble4 1
>
>
>
>
>
> the nibbles are swapped.... depending on access type.... how do we fix
> this... that cuasing me problems in my structure.... write to it using a
> one byte buff[i].. and then i want to access the low-nibble of the 5th
> byte... but it gives me the high-nibble of the 5th byte... becuase of
> swaping... i thought endian problems are only for accessing structures
> larger than bytes.... any one have any ideas how can I get over this
> problem...
>
> thanks...
> Abe
>
> On November 19, 2003 12:27 pm, Garst R. Reese wrote:
> > Sorry, they were in the original fwd.
> > G.
> >
> > Dmitry wrote:
> > > Oops...
> > > where are bitfields?
> > > ~d
> > >
> > > On Wednesday 19 November 2003 18:29, Garst R. Reese wrote:
> > > > Dmitry wrote:
> > > > > hm...
> > > > > any code snippet?
> > > > > ~d
> > > >
> > > > Sure, let me know if you need more.
> > > > Thanks,
> > > > Garst
> > > >
> > > > #ifdef _MMC_TEST
> > > > int main(void)
> > > > {
> > > > unsigned int i;
> > > > union reg16b_t reg16b;
> > > > mcu_init();
> > > > spi_init();
> > > > lcd_init();
> > > > clear_display();
> > > > lcd_set_pos(0,0);
> > > > get_register(MMC_SEND_CSD,®16b);
> > > > print_register(®16b);
> > > > print_response(0xEE);
> > > > print_response(reg16b.csd.READ_BL_LEN);
> > > > SPI_NONE;
> > > > }
> > > > #endif
> > > >
> > > >
> > > > int get_register( unsigned char reg_cmd, union reg16b_t *reg16) {
> > > > unsigned char arguments[4];
> > > > unsigned char temp25;
> > > > int i;
> > > >
> > > > arguments[0]=0x00;
> > > > arguments[1]=0x00;
> > > > arguments[2]=0x00;
> > > > arguments[3]=0x00;
> > > > temp25=mmc_sendcmd(reg_cmd,arguments);
> > > > if(temp25)
> > > > {
> > > > SPI_NONE;
> > > > SPI_LCD_EN;
> > > > lcd_write_string("GETREG");
> > > > print_response(temp25);
> > > > BREAKPNT;
> > > > return FALSE;
> > > > }
> > > > mmc_get_data((unsigned char*) reg16);
> > > > return TRUE;
> > > > }
> > > >
> > > >
> > > > int mmc_get_data(unsigned char* data)
> > > > {
> > > > unsigned char temp25;
> > > > int i ;
> > > >
> > > > while((temp25=mmc_get_response())==0); //if card is busy
> > > > if(temp25!=0xFE)
> > > > {
> > > > BREAKPNT;
> > > > return FALSE;
> > > > }
> > > >
> > > > /*read the data*/
> > > > for(i=0;i<16;i++)
> > > > {
> > > > data[i]=spi_read();
> > > > }
> > > >
> > > > //CRC TOKENs
> > > > spi_read();
> > > > spi_read();
> > > >
> > > > return TRUE;
> > > > }
> > > >
> > > >
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