Datasheet

Library Example
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();
begin
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
end;
// DAC increments (0..4095) --> output voltage (0..Vref)
procedure DAC_Output( valueDAC : word);
var temp : byte;
begin
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
end;
begin
InitMain(); // Perform main initialization
value := 2048; // When program starts, DAC gives
377
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