Mikroelektronika MIKROE-350 Fiche De Données

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
dim Chip_Select as sbit at PORTB.B0

Chip_Select_Direction 

as sbit at DDRB.B0

' End DAC module connections

dim value as word

sub 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)
sub procedure DAC_Output(dim valueDAC as word)
dim temp as byte

Chip_Select = 0                        ' Select DAC chip
' Send High Byte
temp = 

word(valueDAC >> 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

main:

InitMain()         ' Perform main initialization
value = 2048       ' When program starts, DAC gives

'   the output in the mid-range

while TRUE                             ' Endless loop

if  ((PINA0_bit)  and (value < 4095)) then ' If PA0 button is

pressed

Inc(value)                             '   increment value

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