f06x_adc2_externalinput.#2

// This program measures the voltage on an external ADC input and prints the // result to a termin

//-----------------------------------------------------------------------------
// F06x_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.  
// 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 AIN2.1.  
// 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.  
//
// A 100kohm potentiometer may be connected as a voltage divider between 
// VREF and AGND as shown below: (minimum value = 12Kohms as the maximum 
// recommended current through the Vref is of 200uA @2.4V)
//
// ---------
//          |        
//       8 o| AGND ----| 
//         o| VREF ----|<-|
//         o| AIN2.1   |  |
//         o|    |        |
//         o|     -------- 
//         o|
//         o|
//       1 o|
//          |
//----------   
//
// How To Test:
//
// 1) Download code to a 'F06x 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 2.1, or a potentiometer voltage divider as shown above.
// 5) HyperTerminal will print the voltage measured by the device if
//    everything is working properly
//
// FID:            06X000022
// Target:         C8051F06x
// Tool chain:     Keil C51 7.50 / Keil EVAL C51
// Command Line:   None
//
//
// Release 1.0
//    -Initial Revision (CG)
//    -8-June-06
//
//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------

#include <c8051F060.h>                 // SFR declarations
#include <stdio.h>                     

//-----------------------------------------------------------------------------
// 16-bit SFR Definitions for 'F06x
//-----------------------------------------------------------------------------

sfr16 ADC2     = 0xbe;                 // ADC2 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     9600            // Baud rate of UART in bps
#define SYSCLK       24500000          // System Clock
#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 ADC2_Init (void);
void TIMER3_Init (int counts);
void ADC2_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

   ADC2_Init ();                       // Init ADC

   SFRPAGE = ADC2_PAGE;
   AD2EN = 1;                          // Enable ADC

   EA = 1;                             // Enable global interrupts

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

      // The 10-bit ADC2 value is averaged across INT_DEC measurements.  
      // The result is then stored in Result, and is right-justified 
      // The measured voltage applied to AIN 2.1 is then:
      //
      //                           Vref (mV)
      //   measurement (mV) =   --------------- * Result (bits) 
      //                       (2^10)-1 (bits)

      measurement =  Result * 2430 / 1023;

      EA = 1;                          // Re-enable interrupts

      SFRPAGE = UART1_PAGE;

      printf("AIN2.1 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.
//
//-----------------------------------------------------------------------------
void OSCILLATOR_Init (void)
{
   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

   SFRPAGE = SFRPAGE_SAVE;             // Restore SFR page
}

//-----------------------------------------------------------------------------
// PORT_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// This function configures the crossbar and GPIO ports.
//
// P0.4   digital   push-pull     UART TX
// P0.5   digital   open-drain    UART RX
// P1.6   digital   push-pull     LED