這里介紹一個簡單的PIC單片機SPI測試小程序，希望大家能夠喜歡。
- // DAC module connections
- sbit Chip_Select at RC0_bit;
- sbit Chip_Select_Direction at TRISC0_bit;
- // End DAC module connections
- unsigned int value;
- void InitMain() {
- TRISA0_bit = 1; // Set RA0 pin as input
- TRISA1_bit = 1; // Set RA1 pin as input
- Chip_Select = 1; // Deselect DAC
- Chip_Select_Direction = 0; // Set CS# pin as Output
- SPI1_Init(); // Initialize SPI module
- }
- // DAC increments (0..4095) --> output voltage (0..Vref)
- void DAC_Output(unsigned int valueDAC) {
- char temp;
-
- Chip_Select = 0; // Select DAC chip
-
- // Send High Byte
- temp = (valueDAC >> 8) & 0x0F; // Store valueDAC[11..8] to temp[3..0]
- temp |= 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
- }
- void main() {
- ANSEL = 0;
- ANSELH = 0;
- InitMain(); // Perform main initialization
- value = 2048; // When program starts, DAC gives
- // the output in the mid-range
-
- while (1) { // Endless loop
- if ((RA0_bit) && (value < 4095)) { // If RA0 button is pressed
- value++; // increment value
- }
- else {
- if ((RA1_bit) && (value > 0)) { // If RA1 button is pressed
- value--; // decrement value
- }
- }
- DAC_Output(value); // Send value to DAC chip
- Delay_ms(1); // Slow down key repeat pace
- }
- }
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