Software SPI Library

The mikroPascal PRO for ARM 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.

Library configuration:

SPI to Master mode
Clock value = 20 kHz.
Data sampled at the middle of interval.
Clock idle state low.
Data sampled at the middle of interval.
Data transmitted at low to high edge.

The library configures SPI to the master mode, clock = 20kHz, data sampled at the middle of interval, clock idle state low and data transmitted at low to high edge.

Important : The Software SPI library implements time-based activities, so interrupts need to be disabled when using it.

External dependencies of Software SPI Library

Stellaris

The following variables must be defined in all projects using Software SPI Library:	Description :	Example :
`var SoftSpi_SDI : sbit; sfr; external;`	Data In line.	`var SoftSpi_SDI : sbit at GPIO_PORTJ_DATA4_bit;`
`var SoftSpi_SDO : sbit; sfr; external;`	Data Out line.	`var SoftSpi_SDO : sbit at GPIO_PORTJ_DATA5_bit;`
`var SoftSpi_CLK : sbit; sfr; external;`	Clock line.	`var SoftSpi_CLK : sbit at GPIO_PORTJ_DATA3_bit;`
`var SoftSpi_SDI_Direction : sbit; sfr; external;`	Direction of the Data In pin.	`var SoftSpi_SDI_Direction : sbit at GPIO_PORTJ_DIR4_bit;`
`var SoftSpi_SDO_Direction : sbit; sfr; external;`	Direction of the Data Out pin	`var SoftSpi_SDO_Direction : sbit at GPIO_PORTJ_DIR5_bit;`
`var SoftSpi_CLK_Direction : sbit; sfr; external;`	Direction of the Clock pin.	`var SoftSpi_CLK_Direction : sbit at GPIO_PORTJ_DATA3_bit;`

STM32

The following variables must be defined in all projects using Software SPI Library:	Description :	Example :
`var SoftSpi_SDI : sbit; sfr; external;`	Data In line.	`var SoftSpi_SDI : sbit at GPIOD_ODR.B3;`
`var SoftSpi_SDO : sbit; sfr; external;`	Data Out line.	`var SoftSpi_SDO : sbit at GPIOD_ODR.B4;`
`var SoftSpi_CLK : sbit; sfr; external;`	Clock line.	`var SoftSpi_CLK : sbit at GPIOD_ODR.B5;`

Soft_SPI_Init

Prototype	procedure Soft_SPI_Init();
Description	Routine initializes the software SPI module.
Parameters	None.
Returns	Nothing.
Requires	External dependencies of the library from the top of the page must be defined before using this function.
Example	Stellaris // DAC module connections var SoftSpi_CLK : sbit at GPIO_PORTJ_DATA3_bit; SoftSpi_SDI : sbit at GPIO_PORTJ_DATA4_bit; SoftSpi_SDO : sbit at GPIO_PORTJ_DATA5_bit; var SoftSpi_CLK_Direction : sbit at GPIO_PORTJ_DIR3_bit; SoftSpi_SDI_Direction : sbit at GPIO_PORTJ_DIR4_bit; SoftSpi_SDO_Direction : sbit at GPIO_PORTJ_DIR5_bit; // End DAC module connections ... Soft_SPI_Init(); // Init Soft_SPI STM32 // DAC module connections var Chip_Select : sbit at GPIOD_ODR.B1; SoftSpi_CLK : sbit at GPIOD_ODR.B3; SoftSpi_SDI : sbit at GPIOD_ODR.B4; SoftSpi_SDO : sbit at GPIOD_ODR.B5; // End DAC module connections ... Soft_SPI_Init(); // Init Soft_SPI
Notes	None.

Soft_SPI_Read

Prototype	function Soft_SPI_Read(data_ : byte) : byte;
Description	This routine performs 3 operations simultaneously. It provides clock for the Software SPI bus, reads a byte and sends a byte.
Parameters	`sdata:` data to be sent.
Returns	Byte received via the SPI bus.
Requires	Soft SPI must be initialized before using this function. See Soft_SPI_Init routine.
Example	var data_read, data_send : byte; ... // 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);
Notes	None.

Soft_SPI_Write

Prototype	procedure Soft_SPI_Write(sdata : byte);
Description	This routine sends one byte via the Software SPI bus.
Parameters	`sdata:` data to be sent.
Returns	Nothing.
Requires	Soft SPI must be initialized before using this function. See Soft_SPI_Init.
Example	// Write a byte to the Soft SPI bus Soft_SPI_Write(0xAA);
Notes	None.

Library Example

This code demonstrates using library routines for Soft_SPI communication.

Stellaris

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program Soft_SPI;

// DAC module connections
var Chip_Select : sbit at GPIO_PORTJ_DATA1_bit;
    SoftSpi_CLK : sbit at GPIO_PORTJ_DATA3_bit;
    SoftSpi_SDI : sbit at GPIO_PORTJ_DATA4_bit;
    SoftSpi_SDO : sbit at GPIO_PORTJ_DATA5_bit;

var Chip_Select_Direction : sbit at GPIO_PORTJ_DIR1_bit;
    SoftSpi_CLK_Direction : sbit at GPIO_PORTJ_DIR3_bit;
    SoftSpi_SDI_Direction : sbit at GPIO_PORTJ_DIR4_bit;
    SoftSpi_SDO_Direction : sbit at GPIO_PORTJ_DIR5_bit;
// End DAC module connections

var value : word;

procedure InitMain();
  begin
    GPIO_Digital_Input(@GPIO_PORTJ_DATA_BITS, _GPIO_PINMASK_6 or _GPIO_PINMASK_7); // Set PJ6 and PJ7 as digital input
    GPIO_Digital_Output(@GPIO_PORTJ_DATA_BITS, _GPIO_PINMASK_1);                   // Set PJ1 as digital output

    Chip_Select := 1;                       // Deselect DAC
    Soft_Spi_Init();                        // Initialize Soft_SPI
  end;

// DAC increments (0..4095) --> output voltage (0..Vref)
procedure DAC_Output( valueDAC : word);
var temp : byte; volatile;
  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
    Soft_SPI_Write(temp);                    // Send high byte via Soft SPI

    // Send Low Byte
    temp := valueDAC;                        // Store valueDAC[7..0] to temp[7..0]
    Soft_SPI_Write(temp);                    // Send low byte via Soft SPI

    Chip_Select := 1;                        // Deselect DAC chip
  end;

  begin


    InitMain();                              // Perform main initialization

    value := 2048;                           // When program starts, DAC gives
                                             //   the output in the mid-range

    while (TRUE) do                          // Endless loop
      begin

        if ((GPIO_PORTJ_DATA7_bit) and (value < 4095)) then   // If PJ7 button is pressed
          Inc(value)                             //   increment value
        else
          begin
            if ((GPIO_PORTJ_DATA6_bit) and (value > 0)) then  // If PJ6 button is pressed
              Dec(value);                        //   decrement value
          end;

        DAC_Output(value);                       // Send value to DAC chip
        Delay_ms(1);                             // Slow down key repeat pace
      end;
  end.

STM32

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program Soft_SPI;

// DAC module connections
var Chip_Select : sbit at GPIOD_ODR.B1;
    SoftSpi_CLK : sbit at GPIOD_ODR.B3;
    SoftSpi_SDI : sbit at GPIOD_ODR.B4;
    SoftSpi_SDO : sbit at GPIOD_ODR.B5;
// End DAC module connections

var value : word;

procedure InitMain();
  begin
    GPIO_Digital_Input(@GPIOC_BASE,  _GPIO_PINMASK_6 or _GPIO_PINMASK_7); // Set PC6 and PC7 as digital input
    GPIO_Digital_Output(@GPIOD_BASE, _GPIO_PINMASK_1);                    // Set PD1 as digital output

    Chip_Select := 1;                       // Deselect DAC
    Soft_Spi_Init();                        // Initialize Soft_SPI
  end;

// DAC increments (0..4095) --> output voltage (0..Vref)
procedure DAC_Output( valueDAC : word);
var temp : byte; volatile;
  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
    Soft_SPI_Write(temp);                    // Send high byte via Soft SPI

    // Send Low Byte
    temp := valueDAC;                        // Store valueDAC[7..0] to temp[7..0]
    Soft_SPI_Write(temp);                    // Send low byte via Soft SPI

    Chip_Select := 1;                        // Deselect DAC chip
  end;

begin

    InitMain();                              // Perform main initialization

    value := 2048;                           // When program starts, DAC gives
                                             //   the output in the mid-range

    while (TRUE) do                          // Endless loop
      begin

        if ((GPIOC_IDR.B7) and (value < 4095)) then   // If PC7 button is pressed
          Inc(value)                                  //   increment value
        else
          begin
            if ((GPIOC_IDR.B6) and (value > 0)) then  // If PC6 button is pressed
              Dec(value);                             //   decrement value
          end;

        DAC_Output(value);                       // Send value to DAC chip
        Delay_ms(1);                             // Slow down key repeat pace
      end;
end.

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