f06x_adc2_externalinput_mux.c

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

//-----------------------------------------------------------------------------
// F06x_ADC2_ExternalInput_Mux.c
//-----------------------------------------------------------------------------
// Copyright 2005 Silicon Laboratories, Inc.
// http://www.silabs.com
//
// This code example illustrates using the internal analog multiplexer to
// measure analog voltages on up to 8 different analog inputs.  Results are
// printed to a PC terminal program via the UART.
//
// The inputs are sequentially scanned, beginning with input 0 (AIN2.0), up
// to input number <ANALOG_INPUTS>-1 (maximum ANALOG_INPUTS = 8, which will
// scan all analog inputs AIN2.0 - AIN2.7).
//
//
// ADC Settling Time Requirements, Sampling Rate:
// ----------------------------------------------
//
// The total sample time per intput is comprised of an input setting time
// (Tsettle), followed by a conversion time (Tconvert):
//
// Tsample  = Tsettle + Tconvert
//
// Settling and conversion times may overlap, as the ADC holds the value once
// conversion begins.  This code example takes advantage of this to increase
// the settling time above the minimum required.  In other words, when
// converting the value from analog input Ain(n), the input mux is switched
// over to the next input Ain(n+1) to begin settling.
//
// |--------Settling Ain(n)--------|=Conversion Ain(n)=|
//                                 |--------Settling Ain(n+1)--------|=Conversion Ain(n+1)=|
//                                                                   |--------Settling Ain(n+2)--------|
// ISR:  Timer 2                   ^                                 ^                                 ^
// ISR:  ADC2                                          ^                                   ^
//
// The ADC input voltage must be allowed adequate time to settle before the
// conversion is made.  This settling depends on the external source
// impedance, internal mux impedance, and internal capacitance.
// Settling time is given by:
//
//                   | 2^n |
//    Tsettle =   ln | --- | * Rtotal * Csample
//                   | SA  |
//
// In this application, assume a 100kohm potentiometer as the voltage divider.
// The expression evaluates to:
//
//                   | 2^12 |
//    Tsettle =   ln | ---- | * 105e3 * 10e-12 = 10.2uS
//                   | 0.25 |
//
// In addition, one must allow at least 1.5uS after changing analog mux
// inputs or PGA settings.  The settling time in this example, then, is
// dictated by the large external source resistance.
//
// The conversion is 16 periods of the SAR clock <SAR_CLK>.  At 2.5 MHz,
// this time is 16 * 400nS = 6.4 uS.
//
//
// Tsample, minimum  = Tsettle + Tconvert
//                   = 10.2uS + 6.4uS
//                   = 16.6 uS
//
// Timer 2 is set to change the mux input and start a conversion every 20uS.
//
// General:
// --------
//
// 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 array, Result.
//
// The ADC makes repeated measurements at 20uS intervals based on Timer 2.
// The end of each ADC conversion initiates an interrupt which calls an
// averaging function.  <INT_DEC> samples are averaged then the Result
// values 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.  The example
// sequentially scans through the inputs, starting at AIN0.0.  <ANALOG_INPUTS>
// inputs are read.  The 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| AIN2.0   |  |
//         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 AIN2.0 - AIN2.7, or a potentiometer voltage divider as shown above.
///   AIN2.0 - AIN2.7 are shared with  the Port1 pins available on J12
// 5) HyperTerminal will print the voltages measured by the device if
//    everything is working properly.  Note that some of the analog inputs are
//    floating and will return nonzero values.
//
// Target:         C8051F06x
// Tool chain:     Keil C51 7.50 / Keil EVAL C51
// Command Line:   None
//
//
// Release 1.0
//    -Initial Revision SM
//    -21-July-06
//


//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------

#include <c8051f060.h>                 // SFR declarations
#include <stdio.h>

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

sfr16 DP       = 0x82;                 // data pointer
sfr16 RCAP2    = 0xCA;                 // Timer2 reload/capture value
sfr16 RCAP3    = 0xCA;                 // Timer3 reload/capture value
sfr16 RCAP4    = 0xCA;                 // Timer4 reload/capture value
sfr16 TMR2     = 0xCC;                 // Timer2 counter/timer
sfr16 TMR3     = 0xCC;                 // Timer3 counter/timer
sfr16 TMR4     = 0xCC;                 // Timer4 counter/timer
sfr16 ADC2     = 0xBE;                 // ADC2 data
sfr16 ADC0GT   = 0xC4;                 // ADC0 greater than window
sfr16 ADC0LT   = 0xC6;                 // ADC0 less than window
sfr16 DAC0     = 0xD2;                 // DAC0 data
sfr16 DAC1     = 0xD2;                 // DAC1 data
sfr16 CAN0DAT  = 0xD8;                 // CAN data window

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

#define BAUDRATE     115200            // Baud rate of UART in bps
#define SYSCLK       24500000          // Output of PLL derived from (INTCLK*2)
#define INT_DEC      256               // Integrate and decimate ratio
#define SAR_CLK      2500000           // Desired SAR clock speed

#define SAMPLE_DELAY 250               // Delay in ms before displaying sample

#define ANALOG_INPUTS 8                // Number of AIN pins to measure
                                       // (min=1, max=8)

sbit  LED = P1^6;                      // LED: '1' = ON; '0' = OFF


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

void OSCILLATOR_Init (void);
void PORT_Init (void);
void UART1_Init (void);
void ADC2_Init (void);
void TIMER2_Init (void);
void ADC2_ISR (void);
void TIMER2_ISR (void);
void Wait_MS (unsigned int ms);

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

long Result[ANALOG_INPUTS];            // ADC2 decimated value, one for each
                                       // analog input
unsigned char amux_input=0;            // index of analog MUX inputs
unsigned char amux_convert=0;


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

void main (void)
{

   unsigned char i;
   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

   TIMER2_Init ();                     // Initialize Timer2 to overflow at 1 mS

   ADC2_Init ();                       // Init ADC

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

   EA = 1;                             // Enable global interrupts

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

      SFRPAGE = UART1_PAGE;
      printf("\f");
      for(i=0; i<ANALOG_INPUTS; i++)
         {
         // The 10-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 2.1 is then:
         //
         //                           Vref (mV)
         //   measurement (mV) =   --------------- * Result (bits)
         //                       (2^10)-1 (bits)

         measurement =  Result[i] * 2430 / 1023;
         printf("AIN0.%bu voltage: %ld\tmV\n",i,measurement);
         }
      EA = 1;                          // Re-enable interrupts
      Wait_MS(SAMPLE_DELAY);           // Wait before displaying new values
   }
}
//-----------------------------------------------------------------------------
// Initialization Subroutines
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// SYSCLK_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// This routine 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 routine configures the crossbar and GPIO ports.
//
//-----------------------------------------------------------------------------
void PORT_Init (void)
{
   char SFRPAGE_SAVE = SFRPAGE;        // Save Current SFR page

   SFRPAGE = CONFIG_PAGE;              // set SFR page

   XBR0     = 0x00;
   XBR1     = 0x00;
   XBR2     = 0x44;                    // Enable crossbar and weak pull-up
                                       // Enable UART1