C program

Here is the first program we are going to use. We load the code into SDK and compile and link it and then convert the load module to a memory image that we can use in our simulation.

#include "xparameters.h"

#define poke(addr,val)     (*(unsigned char*) (addr) = (val))
#define pokew(addr,val)    (*(unsigned*) (addr) = (val))
#define peek(addr)         (*(unsigned char*) (addr))
#define peekw(addr)        (*(unsigned*) (addr))

int main(void) {  

   unsigned char byte_of_data;
   unsigned      word_of_data;
   int           i,j;
 
   // Define GPIO bus as outputs only
   pokew(XPAR_LCD_16X2_BASEADDR+4,0x00);
  
   // Write data to LCD
   pokew(XPAR_LCD_16X2_BASEADDR,0x7f);
   pokew(XPAR_LCD_16X2_BASEADDR,0x00);
   pokew(XPAR_LCD_16X2_BASEADDR,0x2a);
  
   // Stay in this loop
   while(1);
  
   return 0;
  
  }

Program execution

Here is the result.




Looks perfectly fine to me. So far so good. Let's do the same thing using the Xilinx's software drivers. Like this:

//$$INCLUDE
/*************************************************************************/
/*                                                                       */
/*                I N C L U D E   H E A D E R   F I L E S                */
/*                                                                       */
/*************************************************************************/

#include "xparameters.h"
#include "xgpio.h"

//$$DEFINE
/*************************************************************************/
/*                                                                       */
/*                  D E F I N E   C O N S T A N T S                      */
/*                                                                       */
/*************************************************************************/

// The following constant maps to the name of the hardware instances that
// were created in the EDK XPS system.
 
#define GPIO_LCD_DEVICE_ID    XPAR_LCD_16X2_DEVICE_ID

// The following constant is used to determine which channel of the GPIO is
// used for the LCD if there are 2 channels supported.

#define LCD_CHANNEL 1

// The following are declared globally so they are zeroed and so they are
// easily accessible from a debugger

XGpio GpioLCD;     /* The Instance of the GPIO Driver */

//$$MAIN
/*************************************************************************/
/*                                                                       */
/*                        M A I N   P R O G R A M                        */
/*                                                                       */
/*************************************************************************/

int main(void) {  

    XStatus Status;
   
    // Initialize the GPIO component
    Status = XGpio_Initialize(&GpioLCD, GPIO_LCD_DEVICE_ID);
    if (Status != XST_SUCCESS) return XST_FAILURE;
 
    // Set the direction for all bits to be outputs
    XGpio_SetDataDirection(&GpioLCD,    LCD_CHANNEL, 0x00000000);  
 
    // Write data
    XGpio_DiscreteWrite(&GpioLCD,    LCD_CHANNEL, 0x7f);
    XGpio_DiscreteWrite(&GpioLCD,    LCD_CHANNEL, 0x00);
    XGpio_DiscreteWrite(&GpioLCD,    LCD_CHANNEL, 0x2a);
    while(1);
    return XST_SUCCESS;

  }

Before we continue to compile and build a complete application program let's take a look at Xilinx software platform.

Generating the software libraries and BSPs

For more information about Libgen, refer to the "Library Generator (Libgen)" chapter in the Embedded System Tools Reference Manual. For more information on libraries and device drivers, see the OS and Libraries Document Collection.

The software library for the project is created in the project area:  .../microblaze_0/lib/libxil.a
The address map of the system is created in the header file:  .../microblaze_0/include/xparameters.h

A status message appears in the Console window at the bottom of the SDK main window.

• C Compiler (cc1) – The compiler is responsible for most of the optimizations done on the input C code and generating assembly code.
• C++ Compiler (cc1plus) – The compiler is responsible for most of the optimizations done on the input C++ code and generates assembly code.
  

• C source files
• C++ source files
• Assembly files
• Object files
• Linker scripts

• An ELF file; the default output file name is a.out
• Assembly file, if -save-temps or -S option is used
• Object file, if -save-temps or -c option is used
• Preprocessor output, .i or .ii file, if -save-temps option is used