MSP430 variant 3-wire SPI bus implementation (for DS1302 clock chip)

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MSP430 variant 3-wire SPI bus implementation (for DS1302 clock chip) [Copy link]

As the title says, this is the so-called abnormal version of the 3-wire SPI bus on the Internet: one clock line, one enable line, and one bidirectional IO line.

　　One module, two files:

//spi3.c #include "typedef.h" #include "spi3.h" /******************************************************************** Name: init_spi3 Description: SPI3 initialization function Parameter: (None) Return: (None) Explanation: ***********************************************************************/ void init_spi3(void) { SPI3_DIR |= SPI3_SCLK; SPI3_OUT |= SPI3_SCLK; } /****************************************************************************** * Function: Write a byte to the 3-wire SPI bus, with the low bit first * Parameter: dat - the data byte to be written * Return: * Explanation: **************************************************************************/ void spi3_send_byte(unsigned char dat) { unsigned char cx=8; SPI3_DIR |= SPI3_IO; while(cx--){ if(dat&0x01) SPI3_IO_1; else SPI3_IO_0; SPI3_SCLK_0; SPI3_SCLK_1; dat >>= 1; } } /************************************************************************** * Function: Read a byte from the 3-wire SPI bus * Parameter: * Return: * Description: *****************************************************************************/ unsigned char spi3_recv_byte(void) { unsigned char cx=8; unsigned char dat=0; SPI3_DIR &= ~SPI3_IO; while(cx--){ dat>>=1; if(SPI3_IN & SPI3_IO) dat |= 0x80; else dat &= ~0x80; SPI3_SCLK_0; SPI3_SCLK_1; } return dat; }

//spi3.h
#ifndef __SPI3_H__
#define __SPI3_H__

// Considering that the clock may be controlled externally,
//So I put the definition here
#define SPI3_IN P4IN
#define SPI3_OUT P4OUT
#define SPI3_DIR P4DIR

#define SPI3_IO BIT1
#define SPI3_IO_0 SPI3_OUT &= ~SPI3_IO
#define SPI3_IO_1 SPI3_OUT |= SPI3_IO

#define SPI3_SCLK BIT2
#define SPI3_SCLK_0 SPI3_OUT &= ~SPI3_SCLK
#define SPI3_SCLK_1 SPI3_OUT |= SPI3_SCLK

void init_spi3(void);
void spi3_send_byte(unsigned char dat);
unsigned char spi3_recv_byte(void);
#endif//!__SPI3_H__

typedef.h contains the header file of msp430, as well as some basic and commonly used type definitions. You can define them yourself.