提供一个ch623刷卡芯片通过gpio模拟spi控制的例程

以下是一个使用树莓派的GPIO模拟SPI控制ch623刷卡芯片的例程：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <wiringPi.h>

#define PIN_CLK  17
#define PIN_MOSI 18
#define PIN_MISO 27
#define PIN_CS   22

void spi_init()
{
    wiringPiSetupGpio();
    pinMode(PIN_CLK, OUTPUT);
    pinMode(PIN_MOSI, OUTPUT);
    pinMode(PIN_MISO, INPUT);
    pinMode(PIN_CS, OUTPUT);
    digitalWrite(PIN_CLK, LOW);
    digitalWrite(PIN_MOSI, LOW);
    digitalWrite(PIN_CS, HIGH);
}

void spi_write_byte(unsigned char data)
{
    int i;
    for (i = 0; i < 8; i++) {
        digitalWrite(PIN_MOSI, (data & 0x80) ? HIGH : LOW);
        digitalWrite(PIN_CLK, HIGH);
        data <<= 1;
        digitalWrite(PIN_CLK, LOW);
    }
}

unsigned char spi_read_byte()
{
    int i;
    unsigned char data = 0;
    for (i = 0; i < 8; i++) {
        digitalWrite(PIN_CLK, HIGH);
        data <<= 1;
        if (digitalRead(PIN_MISO) == HIGH)
            data |= 0x01;
        digitalWrite(PIN_CLK, LOW);
    }
    return data;
}

void ch623_select()
{
    digitalWrite(PIN_CS, LOW);
}

void ch623_deselect()
{
    digitalWrite(PIN_CS, HIGH);
}

void ch623_reset()
{
    ch623_select();
    spi_write_byte(0x00);
    spi_write_byte(0x00);
    ch623_deselect();
    usleep(5000);
}

int main()
{
    spi_init();

    ch623_reset();

    return 0;
}

这个例程初始化了树莓派的GPIO，并且定义了使用的引脚。`spi_write_byte`和`spi_read_byte`函数用于发送和接收SPI数据。`ch623_select`和`ch623_deselect`函数用于选择和取消选择ch623芯片。`ch623_reset`函数用于重置芯片。

在`main`函数中，我们通过调用`spi_init`和`ch623_reset`函数来初始化SPI和重置ch623芯片。