Mikroelektronika MIKROE-742 데이터 시트

The code demonstrates how to use SPI library functions for communication between
SPI module of the MCU and Microchip's MCP4921 12-bit D/A converter

program SPI;

// DAC module connections
var Chip_Select : sbit at PORTB.B0;

Chip_Select_Direction : 

sbit at DDRB.B0;

// End DAC module connections

var value : word;

procedure InitMain();

DDA0_bit := 0;                 

// Set PA0 pin as input

DDA1_bit := 0;               

// Set PA1 pin as input

Chip_Select := 1;    

// Deselect DAC

Chip_Select_Direction := 1; 

// Set CS# pin as Output

SPI1_Init();                   

// Initialize SPI1 module

// DAC increments (0..4095) --> output voltage (0..Vref)
procedure DAC_Output( valueDAC : word);
var temp : byte;

Chip_Select := 0;                        // Select DAC chip

// Send High Byte

temp := word(valueDAC 

shr 8) and 0x0F;  // Store valueDAC[11..8]

to temp[3..0]

temp := temp 

or 0x30;             // Define DAC setting, see

MCP4921 datasheet

SPI1_Write(temp);                  // Send high byte via SPI

// Send Low Byte

temp := valueDAC;             // Store valueDAC[7..0] to temp[7..0]

SPI1_Write(temp);         // Send low byte via SPI

Chip_Select := 1;                       // Deselect DAC chip

InitMain();                     // Perform main initialization

value := 2048;                 // When program starts, DAC gives

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