📄 f35x_adc0_externalinput.c
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//-----------------------------------------------------------------------------
// F35x_ADC0_ExternalInput.c
//-----------------------------------------------------------------------------
// Copyright 2006 Silicon Laboratories, Inc.
// http://www.silabs.com
//
// Program Description:
// --------------------
//
// This example code for the C8051F350 takes measurements from input A1N0.2
// using ADC0 then prints the results to a terminal window via the UART.
//
// The system is clocked by the internal 24.5MHz oscillator. The completion of
// this conversion in turn triggers an interrupt service routine (ISR). The ISR
// calculates the ADC0 result into the equivalent mV and then prints the value
// to the terminal via printf before starting another conversion.
//
// The analog multiplexer selects A1N2 as the positive ADC0 input. This
// port is configured as an analog input in the port initialization routine.
// The negative ADC0 input is connected via mux to ground, which provides
// for a single-ended ADC input.
//
// A 100kohm potentiometer may be connected as a voltage divider between
// VREF and AGND on the terminal strip as shown below:
//
// ---------
// |
// o| VREF ----|
// o| GND ---|<-|
// o| AIN2 | |
// o| | |
// o| --------
// o|
// |
//----------
// C8051F350-TB
//
// Terminal output is done via printf, which directs the characters to
// UART0.
//
// F350 Delta-Sigma ADC
// --------------------
// Please see Silicon Labs Applicaton Note AN217 for more information
// on the C8051F35x Delta-Sigma ADC. AN217 can be found on the Applications
// webpage by going to the Silicon Labs Microcontrollers homepage
// (www.silabs.com -> select Microcontrollers under "Products at the top) and
// clicking the gray link on the left.
//
// Direct link:
// http://www.silabs.com/products/microcontroller/applications.asp
//
// F350 Resources:
// ---------------
// Timer1: clocks UART
//
// How To Test:
// ------------
// 1) Download code to a 'F350 device on a C8051F350-TB development board
// 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, or a potentiometer voltage divider as shown above.
// 5) HyperTerminal will print the voltage measured by the device.
//
// FID: 35X000029
// Target: C8051F350
// Tool chain: Keil C51 7.50 / Keil EVAL C51
// Command Line: None
//
// Release 1.0
// -Initial Revision (SM / TP)
// - 8 NOV 2006
//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------
#include <C8051F350.h> // SFR declarations
#include <stdio.h>
//-----------------------------------------------------------------------------
// 16-bit SFR Definitions for 'F35x
//-----------------------------------------------------------------------------
sfr16 TMR2RL = 0xCA; // Timer2 reload value
sfr16 TMR2 = 0xCC; // Timer2 counter
sfr16 ADC0DEC = 0x9A; // ADC0 Decimation Ratio Register
//-----------------------------------------------------------------------------
// Global CONSTANTS
//-----------------------------------------------------------------------------
#define SYSCLK 24500000 // SYSCLK frequency in Hz
#define MDCLK 2457600 // Modulator clock in Hz (ideal is
// (2.4576 MHz)
#define OWR 20 // Desired Output Word Rate in Hz
#define BAUDRATE 115200 // Baud rate of UART in bps
sbit LED = P0^7; // LED='1' means ON
sbit SW2 = P1^0; // SW2='0' means switch pressed
typedef union LONGDATA{ // Access LONGDATA as an
unsigned long result; // unsigned long variable or
unsigned char Byte[4]; // 4 unsigned byte variables
}LONGDATA;
// With the Keil compiler and union byte addressing:
// [0] = bits 31-24, [1] = bits 23-16, [2] = bits 15-8, [3] = bits 7-0
#define Byte3 0
#define Byte2 1
#define Byte1 2
#define Byte0 3
//-----------------------------------------------------------------------------
// Function PROTOTYPES
//-----------------------------------------------------------------------------
void Oscillator_Init (void);
void Port_Init (void);
void UART0_Init (void);
void ADC0_Init(void);
//-----------------------------------------------------------------------------
// MAIN Routine
//-----------------------------------------------------------------------------
void main (void)
{
PCA0MD &= ~0x40; // WDTE = 0 (clear watchdog timer
// enable)
Oscillator_Init(); // Initialize system clock
Port_Init(); // Initialize Crossbar and GPIO
UART0_Init(); // Initialize UART0 for printf's
ADC0_Init(); // Initialize ADC0
AD0INT = 0;
ADC0MD = 0x83; // Start continuous conversions
EA = 1; // Enable global interrupts
while (1) { // Spin forever
}
}
//-----------------------------------------------------------------------------
// Initialization Subroutines
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
// Oscillator_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters : None
//
// This routine initializes the system clock to use the internal 24.5MHz
// oscillator as its clock source. Also enables missing clock detector reset.
//
//-----------------------------------------------------------------------------
void Oscillator_Init (void)
{
OSCICN = 0x83; // Configure internal oscillator for
// its lowest frequency
RSTSRC = 0x04; // Enable missing clock detector
}
//-----------------------------------------------------------------------------
// Port_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters : None
//
// This function initializes the GPIO and the Crossbar
//
// Pinout:
//
// P0.4 - UART TX (digital, push-pull)
// P0.5 - UART RX (digital, open-drain)
//
// AIN0.2 - ADC0 input
//
//-----------------------------------------------------------------------------
void Port_Init (void)
{
XBR0 = 0x01; // UART0 Selected
XBR1 = 0x40; // Enable crossbar and weak pull-ups
P0MDOUT |= 0xD0; // TX, LEDs = Push-pull
}
//-----------------------------------------------------------------------------
// 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
}
//-----------------------------------------------------------------------------
// ADC0_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters : None
//
// Initialize the ADC to use the temperature sensor. (non-differential)
//
//-----------------------------------------------------------------------------
void ADC0_Init (void)
{
REF0CN |= 0x03; // Enable internal Vref
ADC0CN = 0x00; // Gain = 1, Unipolar mode
ADC0CF = 0x00; // Interrupts upon SINC3 filter output
// and uses internal VREF
ADC0CLK = (SYSCLK/MDCLK)-1; // Generate MDCLK for modulator.
// Ideally MDCLK = 2.4576MHz
// Program decimation rate for desired OWR
ADC0DEC = ((unsigned long) MDCLK / (unsigned long) OWR /
(unsigned long) 128) - 1;
ADC0BUF = 0x00; // Turn off Input Buffers
ADC0MUX = 0x28; // Select AIN0.2
ADC0MD = 0x81; // Start internal calibration
while(AD0CALC != 1); // Wait until calibration is complete
EIE1 |= 0x08; // Enable ADC0 Interrupts
ADC0MD = 0x80; // Enable the ADC0 (IDLE Mode)
}
//-----------------------------------------------------------------------------
// Interrupt Service Routines
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
// ADC0_ISR
//-----------------------------------------------------------------------------
//
// This ISR prints the result to the UART. The ISR is called after each ADC
// conversion.
//
//-----------------------------------------------------------------------------
void ADC0_ISR (void) interrupt 10
{
static LONGDATA rawValue;
unsigned long mV;
while(!AD0INT); // Wait till conversion complete
AD0INT = 0; // Clear ADC0 conversion complete flag
// Copy the output value of the ADC
rawValue.Byte[Byte3] = 0x00;
rawValue.Byte[Byte2] = (unsigned char)ADC0H;
rawValue.Byte[Byte1] = (unsigned char)ADC0M;
rawValue.Byte[Byte0] = (unsigned char)ADC0L;
// Vref (mV)
// measurement (mV) = --------------- * result (bits)
// (2^24)-1 (bits)
//
// measurement (mV) = result (bits) / ((2^24)-1 (bits) / Vref (mV))
//
//
// With a Vref (mV) of 2500:
//
// measurement (mV) = result (bits) / ((2^24)-1 / 2500)
//
// measurement (mV) = result (bits) / ((2^24)-1 / 2500)
//
// measurement (mV) = result (bits) / (16777215 / 2500)
//
// measurement (mV) = result (bits) / (6710)
mV = rawValue.result / 6710; // Because of bounds issues, this
// calculation has been manipulated as
// shown above
// (i.e. 2500 (VREF) * 2^24 (ADC result)
// is greater than 2^32)
printf("AIN0.2 voltage: %4ld mV\n",mV);
}
//-----------------------------------------------------------------------------
// End Of File
//-----------------------------------------------------------------------------
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