/* Agilent Spectrum Analyzer Computer Control Demo */
/* Steve Ellingson, 06 Jun 2002 */

/* This software demonstrates how to interface to an Agilent E4407B spectrum analyzer */
/* via RS-232 using C.  Specifically, LabWindows/CVI is used, but only for convenience */
/* in formatting and plotting captured data.  Suggested reference is "ESA Series */
/* Spectrum Analyzers Programmer's Guide" -- but I strongly recommend ignoring the */
/* VISA API strategy used in their examples and using just straight SCPI commands as */
/* I have done here. */

/* To run this demo, first set the analyzer's serial port to run at 115200 (fastest) */
/* and jumper the "AMPTD REF OUT" jack to the "INPUT" jack (this provides a 50 MHz */
/* reference signal at -20 dBm, which gives us something to look at).  When this */
/* program is run, it does the following: */
/* 1. Analyzer is reset to a known condition (factory presets) */
/* 2. 50 MHz reference signal is turned on */
/* 3. Frequency range is set to 10-90 MHz */
/* 4. A single frequency sweep is triggered and captured */
/* 5. The captured trace data is converted to a double-precision array and plotted */
/* 6. Program idles until "QUIT" button is clicked */

/* NOTE: Allow a few seconds for the trace to be plotted after starting the program */


/*--- Header files -----------------------------------------------------*/ 

#include <ansi_c.h>
#include <rs232.h>
#include <formatio.h> /* to allow use of NI's nifty "Scan()" function */ 

/*--- Macro Defines ----------------------------------------------------*/ 

#define TRUE 1
#define FALSE 0

/*--- Globals --------------------------------------------------------*/

/*--- LabWindows/CVI-specific GUI stuff --------------------------------*/

#include "sa_demo.h" /* contains only macro defines for GUI */
#define NO_WAIT		      0
#define NULL_PLOT_HANDLE -1
static int hpMain; 			/* handle to panel "MAIN" */ 

/*======================================================================*/
/*=== main() ===========================================================*/
/*======================================================================*/

void main(void) {

  /*--- LabWindows/CVI-specific GUI stuff -------------------------------*/

  int iControlID;
  int hHandle;
  int bQuit = FALSE;
  
  /*--- Setting up the LabWindows/CVI GUI ---------------------------------*/

  hpMain = LoadPanel (0, "sa_demo.uir", MAIN);
  DisplayPanel (hpMain);
  
  /*--- SA control section ------------------------------------------------*/
  
  {
  char acTxBuffer[256];
  int iStrLen;
  int bDone;
#define BYTES_PER_SWEEP 1611  
  char acSweep[BYTES_PER_SWEEP];
#define POINTS_PER_SWEEP 401
  double x[POINTS_PER_SWEEP];
  double y[POINTS_PER_SWEEP];
  int i;
  
  /* Open COM1 to spectrum analyzer.  */
  /* Assumes spectrum analyzer baud rate set to 115200 bps. Note port config is 8N1 */
  OpenComConfig (1, "COM1", 115200, 0, 8, 1, BYTES_PER_SWEEP+1, 512);
  
  /* Reset spectrum analyzer to factory preset */
  iStrLen = sprintf(acTxBuffer,"%s\n","*RST");
  ComWrt (1, acTxBuffer, iStrLen);
  
  /* Turn on -20 dBm @ 50 MHz cal source; must be jumpered to input on front panel */
  iStrLen = sprintf(acTxBuffer,"%s\n","CAL:SOUR:STAT ON");
  ComWrt (1, acTxBuffer, iStrLen);  
  
  /* Set sweep start frequency */
  iStrLen = sprintf(acTxBuffer,"%s\n","SENS:FREQ:STAR 10 MHZ");
  ComWrt (1, acTxBuffer, iStrLen);		
  
  /* Set sweep stop frequency */
  iStrLen = sprintf(acTxBuffer,"%s\n","SENS:FREQ:STOP 90 MHZ");
  ComWrt (1, acTxBuffer, iStrLen);
  
  /* Set to single sweep mode (vs. default, which is continuous sweep) */
  iStrLen = sprintf(acTxBuffer,"%s\n","INIT:CONT 0");
  ComWrt (1, acTxBuffer, iStrLen);  

  /* Set data format to 32-bit real */
  iStrLen = sprintf(acTxBuffer,"%s\n","FORM:DATA REAL,32");
  ComWrt (1, acTxBuffer, iStrLen);    
  
  /* Set data format binary byte order to SWAP */
  iStrLen = sprintf(acTxBuffer,"%s\n","FORM:BORD SWAP");
  ComWrt (1, acTxBuffer, iStrLen);    
    
  /* Flush input queue */
  FlushInQ (1);  
    
  /* Trigger a sweep */
  iStrLen = sprintf(acTxBuffer,"%s\n","INIT:IMM");
  ComWrt (1, acTxBuffer, iStrLen);
  
  /* Wait for completion */
  /* "*OPC?" prevents new commands from being accepted and */
  /* returns 1 when measurement is complete                */
  iStrLen = sprintf(acTxBuffer,"%s\n","*OPC?"); 
  ComWrt(1,acTxBuffer,iStrLen);  
  
  /* Read one byte at a time, looking for "1" indicating measurement complete */
  bDone = FALSE;
  while (!bDone) {
    if(GetInQLen(1)>0) {
      if (ComRdByte(1)==49) { /* "1" is ASCII 49 */
        bDone=TRUE; 
        ComRdByte(1); /* get the LF character, so it doesn't arrive after we flush the buffer later */
        }
      } /* if(GetInQLen(1)>0) */
    } /* while(!bDone) */ 
  
  /* Flush input queue in preparation for receiving trace data */
  FlushInQ (1);   
  
  /* Request trace data */
  iStrLen = sprintf(acTxBuffer,"%s\n","TRAC:DATA? TRACE1"); 
  ComWrt(1,acTxBuffer,iStrLen);    
  
  /* Wait for BYTES_PER_SWEEP bytes to show up in RX queue */
  while (GetInQLen(1)<BYTES_PER_SWEEP);
  
  /* Transfer sweep data from RX queue to character array */
  ComRd (1, acSweep, BYTES_PER_SWEEP);

  /* Transfer from character array to double-precision array */
  Scan(acSweep,"%401f[b4zi6]>%401f",y);
    /* "b4" tells Scan() to assume 4-byte (as opposed to default 8-byte) reals */
    /* "z" means ignore fact that source array is type char, and typecast as necessary */
    /*  i6 means skip first 6 bytes of capture, which in this case is header information */
 
  /* wait for output queue to empty */
  while (GetOutQLen(1)>0) {}
  
  /* close COM1 */
  CloseCom (1);
  
  /* Show Captured Data */ 
  for (i=0;i<POINTS_PER_SWEEP;i++) x[i] = 10.0 + i*(90.0-10.0)/(POINTS_PER_SWEEP-1); 
  PlotXY (hpMain, MAIN_PSD, x, y, POINTS_PER_SWEEP, VAL_DOUBLE,
		  VAL_DOUBLE, VAL_THIN_LINE, VAL_EMPTY_SQUARE, VAL_SOLID, 1,
		  VAL_YELLOW);
  
  }
  
  /*--- Begin Main Event Loop ------------------------------------------------*/

  while (GetUserEvent(NO_WAIT, &hHandle, &iControlID) || !bQuit) {
  
    if (hHandle==MAIN) {
    
      switch (iControlID) {
	
        case MAIN_QUIT: 
	  	  bQuit = TRUE; 
		  break;
		  
        } /* switch */
      } /* if (hHandle */ 

    } /* while (GetUserEvent */  
    
} /* main() */