max1241.c

AVR单片机的C语言源程序,包括按键扫描EEPROM通讯LCD显示数码管显示等等的源程序DEMO代码

/*************************************************
   Digital voltmeter using an
   Maxim MAX1241 ADC
   connected to an AT90S8515
   using the SPI bus
   The measured voltage is transmitted
   through the STK500 RS232 interface
   Communication parameters: 9600 8N1

   CodeVisionAVR C Compiler
   (C) 2000-2002 HP InfoTech S.R.L.
   www.hpinfotech.ro

   Chip type        : AT90S8515
   Clock frequency  : 3.686400 MHz
   Memory model     : Small
   Internal RAM size: 512
   External RAM size: 0
   Data Stack size  : 128
*************************************************

 	MAX1241 connections to the STK500:
	[MAX1241] [PORTB header]
	1 VDD   - 10 +5V
	2 Vin
	3 /SHDN - 1  PB0
	4 REF   - 10 +5V
	5 GND   - 9  GND
	6 DOUT  - 7  MISO
	7 /CS   - 2  PB1
	8 SCLK  - 8  SCK

   In order to use the RS232 SPARE connector
   on the STK500, the following connections must
   be made:
   [RS232 SPARE header] [PORTD header]
   RXD                - 1 PD0
   TXD                - 2 PD1

   NOTE: AFTER PROGRAMMING THE CHIP, DISCONNECT
   THE 6-WIRE PROGRAMMING CABLE FROM THE SPROG3
   HEADER
*/

#include <90s8515.h>

// Standard Input/Output functions
#include <stdio.h>

// SPI functions
#include <spi.h>

// delays
#include <delay.h>

// MAX1241 Voltage Reference [mV]
#define VREF 5000

// MAX1241 control signals definitions
#define NSHDN PORTB.0
#define NCS PORTB.1
#define DOUT PINB.6

union adcu
          {
          unsigned char byte[2];
          unsigned int word;
          };
          
// Make one AD conversion and return the value
unsigned int max1241_read(void)
{
union adcu adc_data;
// exit MAX1241 from shutdown
NSHDN=1;
// wait 5us for the MAX1241 to wake up
delay_us(5);
// now select the chip to start the conversion
NCS=0;
// wait the conversion to complete
// DOUT will be 0 during conversion
while (DOUT==0);
// DOUT=1 -> conversion completed
// read MSB
adc_data.byte[1]=spi(0);
// read LSB
adc_data.byte[0]=spi(0);
// deselect the chip
NCS=1;
// enter shutdown
NSHDN=0;
// now format the result and return it
return (adc_data.word>>3)&0xfff;
}

void main(void)
{
// store the conversion result here
unsigned n;

// Input/Output Ports initialization
// Port A
DDRA=0x00;
PORTA=0x00;

// Port B
// the /SS pin is set as an output
// with level 1, it's required by
// the SPI to work in master mode
DDRB=0xA3;
PORTB=0x12;

// Port C
DDRC=0x00;
PORTC=0x00;

// Port D
DDRD=0x00;
PORTD=0x00;

// UART initialization
// Communication Parameters: 8 Data, 1 Stop, No Parity
// UART Receiver: Off
// UART Transmitter: On
UCR=0x08;
// UART Baud rate: 9600 @ 3.6864 Mhz
UBRR=23;

// SPI initialization
// SPI Type: Master
// SPI Clock Rate: 921.6 kHz
// SPI Clock Phase: Cycle Half
// SPI Clock Polarity: Low
// SPI Data Order: MSB First
SPCR=0x50;

putsf("MAX1241 Demo using the CodeVisionAVR C Compiler");
putsf("***********************************************\n");

// Make AD conversions and send the results to RS232
while (1)
      {
      n=max1241_read();
      printf("MAX1241-> N=%4u U=%4umV\r\n",n,(unsigned) ((long) n*VREF/4096));
      // 0.3 sec. delay
      delay_ms(300);
      };
}