f33x_adc0_externalinput_mux.c

For C8051F330 This code example illustrates using the internal analog multiplexer to measure analog

// Configure the Crossbar and GPIO ports.
//
// P0.0 - analog (VREF)
// P0.1 - analog input (ADC0)
// P0.2 - analog input (ADC0)
// P0.3 - analog input (ADC0)
// P0.4 - UART TX (push-pull)
// P0.5 - UART RX
// P0.6 - analog input (ADC0)
// P0.7 - analog input (ADC0)
//
//-----------------------------------------------------------------------------
void Port_Init (void)
{
   P0SKIP = 0xCF;                      // Skip all analog pins

   XBR0 = 0x01;                        // UART0 TX and RX pins enabled
   XBR1 = 0x40;                        // Enable crossbar and weak pull-ups

   P0MDOUT |= 0x10;                    // Enable TX0 as a push-pull output

   P0MDIN &= ~0xCF;                    // Set desired pins as analog inputs
}

//-----------------------------------------------------------------------------
// Timer2_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// Configure Timer2 to 16-bit auto-reload and generate an interrupt at 10 us
// intervals.  Timer2 overflows automatically triggers ADC0 conversion.
//
//-----------------------------------------------------------------------------
void Timer2_Init (void)
{
   TMR2CN = 0x00;                      // Stop Timer2; Clear TF2;
                                       // use SYSCLK as timebase, 16-bit
                                       // auto-reload
   CKCON |= 0x10;                      // Select SYSCLK for timer 2 source
   TMR2RL = 65535 - (SYSCLK / 10000);  // Init reload value for 10 us
   TMR2 = 0xffff;                      // Set to reload immediately
   ET2 = 1;                            // Enable Timer2 interrupts
   TR2 = 1;                            // Start Timer2
}

//-----------------------------------------------------------------------------
// ADC0_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// Configures ADC0 to make single-ended analog measurements on Port 0 according
// to the values of <ANALOG_INPUTS> and <PIN_TABLE>.
//
//-----------------------------------------------------------------------------
void ADC0_Init (void)
{
   ADC0CN = 0x02;                      // ADC0 disabled, normal tracking,
                                       // conversion triggered on TMR2 overflow

   REF0CN = 0x03;                      // Enable internal VREF

   AMX0P = PIN_TABLE[0];               // ADC0 initial positive input = P0.1
   AMX0N = 0x11;                       // ADC0 negative input = GND
                                       // i.e., single ended mode

   ADC0CF = ((SYSCLK/3000000)-1)<<3;   // Set SAR clock to 3MHz

   ADC0CF |= 0x00;                     // Right-justify results

   EIE1 |= 0x08;                       // Enable ADC0 EOC interrupt

   AD0EN = 1;                          // Enable ADC0
}

//-----------------------------------------------------------------------------
// UART0_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// Configure the UART0 using Timer1, for <BAUDRATE> and 8-N-1.
//
//-----------------------------------------------------------------------------
void UART0_Init (void)
{
   SCON0 = 0x10;                       // SCON0: 8-bit variable bit rate
                                       //        level of STOP bit is ignored
                                       //        RX enabled
                                       //        ninth bits are zeros
                                       //        clear RI0 and TI0 bits
   if (SYSCLK/BAUDRATE/2/256 < 1) {
      TH1 = -(SYSCLK/BAUDRATE/2);
      CKCON |=  0x08;                  // T1M = 1; SCA1:0 = xx
   } else if (SYSCLK/BAUDRATE/2/256 < 4) {
      TH1 = -(SYSCLK/BAUDRATE/2/4);
      CKCON &= ~0x0B;                  // T1M = 0; SCA1:0 = 01
      CKCON |=  0x01;
   } else if (SYSCLK/BAUDRATE/2/256 < 12) {
      TH1 = -(SYSCLK/BAUDRATE/2/12);
      CKCON &= ~0x0B;                  // T1M = 0; SCA1:0 = 00
   } else if (SYSCLK/BAUDRATE/2/256 < 48) {
      TH1 = -(SYSCLK/BAUDRATE/2/48);
      CKCON &= ~0x0B;                  // T1M = 0; SCA1:0 = 10
      CKCON |=  0x02;
   } else {
      while (1);                       // Error.  Unsupported baud rate
   }

   TL1 = TH1;                          // Init Timer1
   TMOD &= ~0xF0;                      // TMOD: timer 1 in 8-bit autoreload
   TMOD |=  0x20;
   TR1 = 1;                            // START Timer1
   TI0 = 1;                            // Indicate TX0 ready
}

//-----------------------------------------------------------------------------
// Interrupt Service Routines
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// Timer2_ISR
//-----------------------------------------------------------------------------
//
// This routine changes to the next Analog MUX input whenever Timer2 overflows
// for the next ADC sample.  This allows the ADC to begin setting on the new
// input while converting the old input.
//
//-----------------------------------------------------------------------------
void Timer2_ISR (void) interrupt 5
{
   TF2H = 0;                           // Clear Timer2 interrupt flag

   // Set up the AMUX for the next ADC input
   // ADC0 positive input = P0.<PIN_TABLE[AMUX_INPUT+1]>
   // ADC0 negative input = GND
   // i.e., single ended mode
   if (AMUX_INPUT == (ANALOG_INPUTS - 1))
   {
      AMX0P = PIN_TABLE[0];
   }
   else
   {
      AMX0P = PIN_TABLE[AMUX_INPUT+1];
   }
}

//-----------------------------------------------------------------------------
// ADC0_ISR
//-----------------------------------------------------------------------------
//
// This ISR averages <INT_DEC> samples for each analog MUX input then prints
// the results to the terminal.  The ISR is called after each ADC conversion,
// which is triggered by Timer2.
//
//-----------------------------------------------------------------------------
void ADC0_ISR (void) interrupt 10
{
   static unsigned int_dec = INT_DEC;  // Integrate/decimate counter
                                       // A new result is posted when
                                       // int_dec is 0

   // Integrate accumulator for the ADC samples from input pins
   static long accumulator[ANALOG_INPUTS] = 0x00000000;

   unsigned char i;                    // Loop counter


   AD0INT = 0;                         // Clear ADC conversion complete
                                       // overflow


   accumulator[AMUX_INPUT] += ADC0;    // Read the ADC value and add it to the
                                       // running total

   // Reset sample counter <int_dec> and <AMUX_INPUT> if the final input was
   // just read
   if(AMUX_INPUT == (ANALOG_INPUTS - 1))
   {
      int_dec--;                       // Update decimation counter
                                       // when the last of the analog inputs
                                       // is sampled

      if (int_dec == 0)                // If zero, then post the averaged
      {                                // results
         int_dec = INT_DEC;            // Reset counter

         // Copy each averaged ADC0 value into the RESULT array
         for(i = 0; i < ANALOG_INPUTS; i++)
         {
            // Copy averaged values into RESULT
            RESULT[i] = accumulator[i] / int_dec;

            // Reset accumulators
            accumulator[i] = 0x00000000;
         }
      }

      AMUX_INPUT = 0;                  // Reset input index back to P0.1
   }
   // Otherwise, increment the AMUX channel counter
   else
   {
      AMUX_INPUT++;                    // Step to the next analog mux input
   }
}

//-----------------------------------------------------------------------------
// Support Subroutines
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// Timer0_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   :
//   1) int ms - number of milliseconds to wait
//                        range is positive range of an int: 0 to 32767
//
// This function configures the Timer0 as a 16-bit timer, interrupt enabled.
// Using the internal osc. at 24.5MHz with a prescaler of 1:8 and reloading the
// T0 registers with TIMER0_RELOAD_HIGH/LOW, it will wait for <ms>
// milliseconds.
// Note: The Timer0 uses a 1:12 prescaler
//-----------------------------------------------------------------------------
void Timer0_wait(int ms)
{
   TH0 = TIMER0_RELOAD_HIGH;           // Init Timer0 High register
   TL0 = TIMER0_RELOAD_LOW ;           // Init Timer0 Low register
   TMOD |= 0x01;                       // Timer0 in 16-bit mode
   CKCON &= 0xFC;                      // Timer0 uses a 1:12 prescaler
   TR0  = 1;                           // Timer0 ON

   while(ms)
   {
      TF0 = 0;                         // Clear flag to initialize
      while(!TF0);                     // Wait until timer overflows
      ms--;                            // Decrement ms
   }

   TR0 = 0;                            // Timer0 OFF
}

//-----------------------------------------------------------------------------
// End Of File
//-----------------------------------------------------------------------------