📄 f00x_adc0_externalinput.c
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//-----------------------------------------------------------------------------
// F00x_ADC0_ExternalInput.c
//-----------------------------------------------------------------------------
// Copyright 2006 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 an external 22.1184 MHz crystal 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 AIN0. 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
// C8051F005-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 | |
// o| | |
// o| --------
// o|
// o|
// 1 o|
// |
//----------
//
// How To Test:
//
// 1) Download code to a 'F005 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 AIN0, or a potentiometer voltage divider as shown above.
// 5) HyperTerminal will print the voltage measured by the device if
// everything is working properly
//
// Target: C8051F005
// Tool chain: Keil C51 7.50 / Keil EVAL C51
// Command Line: None
//
//
// Release 1.0
// -Initial Revision (PD)
// -27-Jul-06
//
//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------
#include <c8051f000.h> // SFR declarations
#include <stdio.h>
//-----------------------------------------------------------------------------
// 16-bit SFR Definitions for 'F00x
//-----------------------------------------------------------------------------
sfr16 DP = 0x82; // data pointer
sfr16 TMR3RL = 0x92; // Timer3 reload value
sfr16 TMR3 = 0x94; // Timer3 counter
sfr16 ADC0 = 0xbe; // ADC0 data
sfr16 ADC0GT = 0xc4; // ADC0 greater than window
sfr16 ADC0LT = 0xc6; // ADC0 less than window
sfr16 RCAP2 = 0xca; // Timer2 capture/reload
sfr16 T2 = 0xcc; // Timer2
sfr16 DAC0 = 0xd2; // DAC0 data
sfr16 DAC1 = 0xd5; // DAC1 data
//-----------------------------------------------------------------------------
// Global Constants
//-----------------------------------------------------------------------------
#define BAUDRATE 115200 // Baud rate of UART in bps
#define SYSCLK 22118400 // External crystal oscillator frequency
#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 UART0_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
UART0_Init (); // Initialize UART1
TIMER3_Init (SYSCLK/SAMPLE_RATE); // Initialize Timer3 to overflow at
// sample rate
ADC0_Init (); // Init ADC
ADCEN = 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
printf("AIN0.1 voltage: %ld mV\n",measurement);
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 an external 22.1184MHz
// crystal.
//
//-----------------------------------------------------------------------------
void OSCILLATOR_Init (void)
{
int i; // Software timer
OSCICN |= 0x80; // Enable the missing clock detector
// Initialize external crystal oscillator to use 22.1184 MHz crystal
OSCXCN = 0x67; // Enable external crystal osc.
for (i =0 ; i < 256; i++); // Wait at least 1 ms
while (!(OSCXCN & 0x80)); // Wait for crystal osc to settle
OSCICN |= 0x08; // Select external clock source
OSCICN &= ~0x04; // Disable the internal osc.
}
//-----------------------------------------------------------------------------
// PORT_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters : None
//
// This function configures the crossbar and GPIO ports.
//
// P0.0 digital push-pull UART TX
// P0.1 digital open-drain UART RX
// AIN0 analog Analog input (no configuration necessary)
//
//-----------------------------------------------------------------------------
void PORT_Init (void)
{
XBR0 = 0x04; // Enable UART0
XBR1 = 0x00;
XBR2 = 0x40; // Enable crossbar and weak pull-ups
PRT0CF |= 0x01; // enable TX0 as a push-pull output
PRT1CF |= 0x40; // enable P1.6 (LED) as push-pull output
}
//-----------------------------------------------------------------------------
// UART0_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters : None
//
// Configure the UART using Timer1, for <baudrate> and 8-N-1.
//
//----------------------------------------------------------------------------
void UART0_Init (void)
{
SCON = 0x50; // SCON: mode 1, 8-bit UART, enable RX
TMOD = 0x20; // TMOD: timer 1, mode 2, 8-bit reload
TH1 = -(SYSCLK/BAUDRATE/16); // set Timer1 reload value for baudrate
TR1 = 1; // start Timer1
CKCON |= 0x10; // Timer1 uses SYSCLK as time base
PCON |= 0x80; // SMOD = 1
TI = 1; // Indicate TX ready
}
//-----------------------------------------------------------------------------
// ADC0_Init
//-----------------------------------------------------------------------------
//
// Configure ADC0 to use Timer3 overflows as conversion source, to
// generate an interrupt on conversion complete, and to use left-justified
// output mode. Enables ADC end of conversion interrupt. Leaves ADC disabled.
//
//----------------------------------------------------------------------------
void ADC0_Init (void)
{
ADC0CN = 0x04; // ADC0 disabled; normal tracking
// mode; ADC0 conversions are initiated
// on overflow of Timer3; ADC0 data is
// right-justified
REF0CN = 0x07; // enable temp sensor, on-chip VREF,
// and VREF output buffer
AMX0SL = 0x00; // Select AIN0 as ADC mux output
ADC0CF = 0x80; // ADC conversion clock = SYSCLK/16
ADC0CF &= ~0x07; // PGA gain = 1
EIE2 |= 0x02; // enable ADC interrupts
}
//-----------------------------------------------------------------------------
// TIMER3_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters :
// 1) int counts - calculated Timer overflow rate
// range is postive range of integer: 0 to 32767
//
// Configure Timer3 to auto-reload at interval specified by <counts> (no
// interrupt generated) using SYSCLK as its time base.
//
//----------------------------------------------------------------------------
void Timer3_Init (int counts)
{
TMR3CN = 0x02; // Stop Timer3; Clear TF3;
// use SYSCLK as timebase
TMR3RL = -counts; // Init reload values
TMR3 = 0xffff; // set to reload immediately
EIE2 &= ~0x01; // disable Timer3 interrupts
TMR3CN |= 0x04; // start Timer3
}
//-----------------------------------------------------------------------------
// Interrupt Service Routines
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
// ADC0_ISR
//-----------------------------------------------------------------------------
//
// Here we take the ADC0 sample, add it to a running total <accumulator>, and
// decrement our local decimation counter <int_dec>. When <int_dec> reaches
// zero, we post the decimated result in the global variable <Result>.
//
//-----------------------------------------------------------------------------
void ADC0_ISR (void) interrupt 15
{
static unsigned int_dec=INT_DEC; // Integrate/decimate counter
// we post a new result when
// int_dec = 0
static long accumulator=0L; // Here's where we integrate the
// ADC samples
ADCINT = 0; // clear ADC conversion complete
// indicator
accumulator += ADC0; // Read ADC value and add to running
// total
int_dec--; // Update decimation counter
if (int_dec == 0) // If zero, then post result
{
int_dec = INT_DEC; // Reset counter
Result = accumulator >> 8;
accumulator = 0L; // Reset accumulator
}
}
//-----------------------------------------------------------------------------
// Support Subroutines
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
// Wait_MS
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters:
// 1) unsigned int ms - number of milliseconds of delay
// range is full range of integer: 0 to 65335
//
// This routine inserts a delay of <ms> milliseconds.
//
//-----------------------------------------------------------------------------
void Wait_MS(unsigned int ms)
{
CKCON &= ~0x20; // use SYSCLK/12 as timebase
RCAP2 = -(SYSCLK/1000/12); // Timer 2 overflows at 1 kHz
T2 = RCAP2;
ET2 = 0; // Disable Timer 2 interrupts
TR2 = 1; // Start Timer 2
while(ms)
{
TF2 = 0; // Clear flag to initialize
while(!TF2); // Wait until timer overflows
ms--; // Decrement ms
}
TR2 = 0; // Stop Timer 2
}
//-----------------------------------------------------------------------------
// End Of File
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