adc_186.c

使用picc开发的使用spi总线控制AD和DA芯片的源程序

//   ANALOGUE TO DIGITAL CONVERTER HARDWARE INTERFACE PROGRAM
//   COPYRIGHT PROPERTY OF ALPHADATA DESIGNS LIMITED (c) 1999
//   WRITTEN FOR THE MAX186 12 BIT 8-CHANNEL MICRO-WIRE A TO D

//   published by permission of Alphadata designs on
//   Hi-Tech C website, http://www.workingtex.com/htpic.  Thanks!

//------------------------------------------------------
// Version History
//------------------------------------------------------
// Issue 1.0 : 21/12/1999 : First Officially Released
//------------------------------------------------------

#include "ioh8314.h"
#include "h8genlib.h"
#include "spi.h"

extern byte p4dr;

/* call this to set up the hardware ports */

void adc_initialise(void)
{
}

/* this table makes up the muddled way the device is addressed */
/* see the data sheet for the MAX186 to see why !              */
const byte command_table[]={	0b10001111,
				0b11001111,
				0b10011111,
				0b11011111,

				0b10101111,
				0b11101111,
				0b10111111,
				0b11111111};

/* call this to read one channel of data from the a to d */

word adc_read_channel(byte channel_number)
{
	byte	bits;
	byte	command;
	int	data;

	spi_adc_select();

  	/* Start by sending command byte */
  	command = command_table[channel_number];

  	for (bits=0;bits<8;bits++) {

	  	if ((command & 0x80) == 0) spi_lodata(); else spi_hidata();
		command = command << 1;

		spi_hiclock();
		spi_loclock();

  	}

  	spi_lodata();
  	spi_hiclock();
  	spi_loclock();

  	data = 0;
  	for (bits=0;bits<12;bits++) {

		data = (data << 1);
		if (P4DR & 0b10000000) data = data | 0x0001;

		spi_hiclock();
		spi_loclock();

  	}

  	spi_adc_deselect();

  	return (data);

}

// does an average reading

word adc_filtered_read(byte channel,int readings)
{
	long	av;
	word	lp;

	av = 0;

	for (lp=0;lp<readings;lp++) {

		av = av + adc_read_channel(channel);

	}

	return (word)(av / readings);
}

// end