f12x_adc0_externalinput.c

C8051F120CPU的AD读写程序

//-----------------------------------------------------------------------------
// F12x_ADC0_ExternalInput.c
//-----------------------------------------------------------------------------
// Copyright 2005 Silicon Laboratories, Inc.
// http://www.silabs.com
//
// Program Description:
//
// This program measures the voltage on an external ADC input and prints the 
// result to a terminal window via the UART.
//
// The system is clocked using the internal 24.5MHz oscillator multiplied
// up to 49MHz by the on-chip PLL.  Results are printed to the UART from a loop
// with the rate set by a delay based on Timer 2.  This loop periodically reads
// the ADC value from a global variable, Result.
//
// The ADC makes repeated measurements at a rate determined by SAMPLE_RATE using
// Timer 3.  The end of each ADC conversion initiates an interrupt which calls an 
// averaging function.  <INT_DEC> samples are averaged then the Result value updated.
//
// For each power of 4 of <INT_DEC>, you gain 1 bit of effective resolution.
// For example, <INT_DEC> = 256 gain you 4 bits of resolution: 4^4 = 256.
// 
// The ADC input multiplexer is set for a single-ended input at AIN0.1.  The input
// amplifier is set for unity gain so a voltage range of 0 to Vref (2.43V) may
// be measured.  Although voltages up to Vdd may be applied without damaging the
// device, only the range 0 to Vref may be measured by the ADC.  
// The input is available at the 8-position board-edge connector, J20, on the 
// C8051FX20-TB.
//
// A 100kohm potentiometer may be connected as a voltage divider between 
// VREF and AGND as shown below:
//
// ---------
//          |        
//       8 o| AGND ----| 
//         o| VREF ----|<-|
//         o| AIN0.1   |  |
//         o|    |        |
//         o|     -------- 
//         o|
//         o|
//       1 o|
//          |
//----------   
//
// How To Test:
//
// 1) Download code to a 'F12x device that is connected to a UART transceiver
// 2) Connect serial cable from the transceiver to a PC
// 3) On the PC, open HyperTerminal (or any other terminal program) and connect
//    to the COM port at <BAUDRATE> and 8-N-1
// 4) Connect a variable voltage source (between 0 and Vref) 
//    to AIN 0.1, or a potentiometer voltage divider as shown above.
// 5) HyperTerminal will print the voltage measured by the device if
//    everything is working properly
//
// FID:            12X000022
// Target:         C8051F12x
// Tool chain:     Keil C51 7.50 / Keil EVAL C51
// Command Line:   None
//
//
// Release 1.0
//    -Initial Revision (clm)
//    -19-May-06
//
//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------

#include <c8051f120.h>                 // SFR declarations
#include <stdio.h>                     

//-----------------------------------------------------------------------------
// 16-bit SFR Definitions for 'F12x
//-----------------------------------------------------------------------------

sfr16 ADC0     = 0xbe;                 // ADC0 data
sfr16 RCAP2    = 0xca;                 // Timer2 capture/reload
sfr16 RCAP3    = 0xca;                 // Timer3 capture/reload
sfr16 TMR2     = 0xcc;                 // Timer2
sfr16 TMR3     = 0xcc;                 // Timer3

//-----------------------------------------------------------------------------
// Global Constants
//-----------------------------------------------------------------------------

#define BAUDRATE     115200            // Baud rate of UART in bps
#define SYSCLK       49000000          // Output of PLL derived from (INTCLK*2)
#define SAMPLE_RATE  50000             // Sample frequency in Hz
#define INT_DEC      256               // Integrate and decimate ratio
#define SAR_CLK      2500000           // Desired SAR clock speed

#define SAMPLE_DELAY 50                // Delay in ms before taking sample

sbit LED = P1^6;                       // LED='1' means ON
sbit SW1 = P3^7;                       // SW1='0' means switch pressed

//-----------------------------------------------------------------------------
// Function Prototypes
//-----------------------------------------------------------------------------

void OSCILLATOR_Init (void);           
void PORT_Init (void);
void UART1_Init (void);
void ADC0_Init (void);
void TIMER3_Init (int counts);
void ADC0_ISR (void);
void Wait_MS (unsigned int ms);

//-----------------------------------------------------------------------------
// Global Variables
//-----------------------------------------------------------------------------

long Result;                           // ADC0 decimated value

//-----------------------------------------------------------------------------
// main() Routine
//-----------------------------------------------------------------------------

void main (void)
{
   long measurement;                   // Measured voltage in mV

   WDTCN = 0xde;                       // Disable watchdog timer
   WDTCN = 0xad;

   OSCILLATOR_Init ();                 // Initialize oscillator
   PORT_Init ();                       // Initialize crossbar and GPIO
   UART1_Init ();                      // Initialize UART1
   TIMER3_Init (SYSCLK/SAMPLE_RATE);   // Initialize Timer3 to overflow at
                                       // sample rate

   ADC0_Init ();                       // Init ADC

   SFRPAGE = ADC0_PAGE;
   AD0EN = 1;                          // Enable ADC

   EA = 1;                             // Enable global interrupts

   while (1)
   {
      EA = 0;                          // Disable interrupts

      // The 12-bit ADC value is averaged across INT_DEC measurements.  The result is 
      // then stored in Result, and is right-justified 
      // The measured voltage applied to AIN 0.1 is then:
      //
      //                           Vref (mV)
      //   measurement (mV) =   --------------- * Result (bits) 
      //                       (2^12)-1 (bits)

      measurement =  Result * 2430 / 4095;

      EA = 1;                          // Re-enable interrupts

      SFRPAGE = UART1_PAGE;

      printf("AIN0.1 voltage: %ld mV\n",measurement);

      SFRPAGE = CONFIG_PAGE;
      LED = ~SW1;                      // LED reflects state of switch

      Wait_MS(SAMPLE_DELAY);           // Wait 50 milliseconds before taking
                                       // another sample
   }
}

//-----------------------------------------------------------------------------
// Initialization Subroutines
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// OSCILLATOR_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// This function initializes the system clock to use the internal oscillator
// at 24.5 MHz multiplied by two using the PLL.
//
//-----------------------------------------------------------------------------
void OSCILLATOR_Init (void)
{
   int loop;                           // Software timer

   char SFRPAGE_SAVE = SFRPAGE;        // Save Current SFR page

   SFRPAGE = CONFIG_PAGE;              // Set SFR page

   OSCICN = 0x83;                      // Set internal oscillator to run
                                       // at its maximum frequency

   CLKSEL = 0x00;                      // Select the internal osc. as
                                       // the SYSCLK source

   //Turn on the PLL and increase the system clock by a factor of M/N = 2
   SFRPAGE = CONFIG_PAGE;

   PLL0CN  = 0x00;                     // Set internal osc. as PLL source
   SFRPAGE = LEGACY_PAGE;
   FLSCL   = 0x10;                     // Set FLASH read time for 50MHz clk
                                       // or less
   SFRPAGE = CONFIG_PAGE;
   PLL0CN |= 0x01;                     // Enable Power to PLL
   PLL0DIV = 0x01;                     // Set Pre-divide value to N (N = 1)
   PLL0FLT = 0x01;                     // Set the PLL filter register for
                                       // a reference clock from 19 - 30 MHz
                                       // and an output clock from 45 - 80 MHz
   PLL0MUL = 0x02;                     // Multiply SYSCLK by M (M = 2)

   for (loop=0; loop < 256; loop++);   // Wait at least 5us
   PLL0CN  |= 0x02;                    // Enable the PLL
   while(!(PLL0CN & 0x10));            // Wait until PLL frequency is locked
   CLKSEL  = 0x02;                     // Select PLL as SYSCLK source

   SFRPAGE = SFRPAGE_SAVE;             // Restore SFR page
}

//-----------------------------------------------------------------------------
// PORT_Init
//-----------------------------------------------------------------------------
//
// Return Value : None