Software SPI Library
The mikroC PRO for 8051 provides routines for implementing Software SPI communication. These routines are hardware independent and can be used with any MCU. The Software SPI Library provides easy communication with other devices via SPI: A/D converters, D/A converters, MAX7219, LTC1290, etc.
- SPI to Master mode
- Clock value = 20 kHz.
- Clock idle state low.
- Data sampled at the middle of interval.
- Data transmitted at low to high edge.
Note: The Software SPI library implements time-based activities, so interrupts need to be disabled when using it.
External dependencies of Software SPI Library
The following variables must be defined in all projects using Software SPI Library: | Description : | Example : |
---|---|---|
extern sfr sbit bdata SoftSpi_SDI; |
Data In line. | sbit SoftSpi_SDI at P1_6_bit; |
extern sfr sbit bdata SoftSpi_SDO; |
Data Out line. | sbit SoftSpi_SDO at P1_5_bit; |
extern sfr sbit bdata SoftSpi_CLK; |
Clock line. | sbit SoftSpi_CLK at P1_7_bit; |
Library Routines
Soft_SPI_Init
Prototype |
void Soft_SPI_Init(); |
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Returns |
Nothing. |
Description |
Configures and initializes the software SPI module. |
Requires |
Global variables:
|
Example |
// soft_spi pinout definition sbit SoftSpi_SDI at P1_6_bit; sbit SoftSpi_SDO at P1_5_bit; sbit SoftSpi_CLK at P1_7_bit; ... Soft_SPI_Init(); // Init Soft_SPI |
Soft_SPI_Read
Prototype |
unsigned short Soft_SPI_Read(char sdata); |
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Returns |
Byte received via the SPI bus. |
Description |
This routine performs 3 operations simultaneously. It provides clock for the Software SPI bus, reads a byte and sends a byte. Parameters :
|
Requires |
Soft SPI must be initialized before using this function. See Soft_SPI_Init routine. |
Example |
unsigned short data_read; char data_send; ... // Read a byte and assign it to data_read variable // (data_send byte will be sent via SPI during the Read operation) data_read = Soft_SPI_Read(data_send); |
Soft_SPI_Write
Prototype |
void Soft_SPI_Write(char sdata); |
---|---|
Returns |
Nothing. |
Description |
This routine sends one byte via the Software SPI bus. Parameters :
|
Requires |
Soft SPI must be initialized before using this function. See Soft_SPI_Init routine. |
Example |
// Write a byte to the Soft SPI bus Soft_SPI_Write(0xAA); |
Library Example
This code demonstrates using library routines for Soft_SPI communication. Also, this example demonstrates working with Port Expander MCP23S17.
// Port Expander module connections sbit SPExpanderRST at P1_0_bit; sbit SPExpanderCS at P1_1_bit; // End Port Expander module connections // Software SPI connections sbit SoftSpi_CLK at P1_7_bit; sbit SoftSpi_SDI at P1_6_bit; sbit SoftSpi_SDO at P1_5_bit; // End Software SPI connections char (*SPI_Rd_Ptr)(char); // Pointer to SPI_Read function // used by Port Expander Library unsigned char i = 0; void main() { SPI_Rd_Ptr = Soft_SPI_Read; // Link Port Expander Library to Software SPI library Expander_Init(0); // Initialize Port Expander Expander_Set_DirectionPortA(0, 0x00); // Set Expander's PORTA to be output Expander_Set_DirectionPortB(0,0xFF); // Set Expander's PORTB to be input Expander_Set_PullUpsPortB(0,0xFF); // Set pull-ups to all of the Expander's PORTB pins while(1) { // Endless loop Expander_Write_PortA(0, i++); // Write i to expander's PORTA P2 = Expander_Read_PortB(0); // Read expander's PORTB and write it to PORT2 LEDs Delay_ms(100); } }
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