ADS1110: arm-linux读取数据，dta位存在台阶形毛刺（无法上拉）的情况

  我在arm-linux下使用libi2c和gpio模拟i2c，尝试读取ADS111x的数据，但是存在台阶形状毛刺，具体如下图所示。使用的设备为Licheepi Nano，所用的芯片为F1C100S。

可以看到，输入位1.5v时，D14因该为1，但是次数没有被上拉，形成了一台台阶状的毛刺；同时低八位也存在两个台阶毛刺。但是Config位却能够被正确读取。代码如下：

#define NUMS 10
char readbuf[NUMS];

int main(int argc, char** argv)
{
    int file = open("/dev/i2c-0", O_RDWR);

    // addr = 1001 xxx
    int addr = 0b1001000;

    if (file < 0)
    {
        printf("openfile error!\n");
        exit(1);
    }

    if (ioctl(file, I2C_SLAVE, addr) < 0)
    {
        printf("ioctl error!\n");
        exit(1);
    }

    // Debug Gain 1
    readbuf[0] = 0x0C;

    if (write(file, readbuf, 1) != 1)
    {
        printf("write error!\n");
        exit(1);
    }

    if (read(file, readbuf, 3) != 3)
    {
        printf("read error!\n");
        exit(1);
    }

    printf("%x %x %x\n", readbuf[0] & 0xff, readbuf[1] & 0xff, readbuf[2] & 0xff);

    close(file);

    exit(EXIT_SUCCESS);
}

同时，我使用GPIO模拟I2C，仍然存在上述问题，波形如下图所示：

代码如下，gpio.h：

struct gpiod_chip* gpiochip0;
struct gpiod_line* line_SCL;
struct gpiod_line* line_SDA;

int PE11Num = (4 * 32) + 11;
int PE12Num = (4 * 32) + 12;

bool i2cInit()
{
    gpiochip0 = gpiod_chip_open("/dev/gpiochip0");
    line_SCL = gpiod_chip_get_line(gpiochip0, PE11Num);
    line_SDA = gpiod_chip_get_line(gpiochip0, PE12Num);

    int reqSCL = gpiod_line_request_output(line_SCL, "SCL", 1);
    int reqSDA = gpiod_line_request_output(line_SDA, "SDA", 1);

    return !(reqSCL | reqSDA);
}

bool i2cSDAConf(bool toOutput)
{
    int reqSDA;

    gpiod_line_release(line_SDA);

    if (toOutput)
    {
        int reqSDA = gpiod_line_request_output(line_SDA, "SDA", 1);
    }
    else
    {
        int reqSDA = gpiod_line_request_input(line_SDA, "SDA");
    }

    return !reqSDA;
}

void i2cSDALevel(bool toHigh)
{
    gpiod_line_set_value(line_SDA, toHigh);
}

void i2cSCLLevel(bool toHigh)
{
    gpiod_line_set_value(line_SCL, toHigh);
}

void i2cDelay()
{
    for (int i = 0; i < 1000; ++i) { /* do nothing */ }
}

void i2cStart()
{
    i2cSDALevel(1);
    i2cSCLLevel(1);
    i2cDelay();
    i2cSDALevel(0);
    i2cDelay();
    i2cSCLLevel(0);
    i2cDelay();
}

void i2cEnd()
{
    i2cSDALevel(0);
    i2cDelay();
    i2cSCLLevel(1);
    i2cDelay();
    i2cSDALevel(1);
}

void i2cACK()
{
    // make sure the SDA is output before send
    i2cSDAConf(1);

    i2cSDALevel(0);
    i2cDelay();
    i2cSCLLevel(1);
    i2cDelay();
    i2cSCLLevel(0);
    i2cDelay();
}

void i2cNACK()
{
    // make sure the SDA is output before send
    i2cSDAConf(1);

    i2cSDALevel(1);
    i2cDelay();
    i2cSCLLevel(1);
    i2cDelay();
    i2cSCLLevel(0);
    i2cDelay();
}

bool i2cSDARelease()
{
    // i2cSDALevel(0);
    return i2cSDAConf(0);
}

bool i2cWaitAck()
{
    return !i2cGetSDA();
}

void i2cSend(u8 data)
{
    // make sure the SDA is output before send
    i2cSDAConf(1);

    for (int i = 0; i < 8; ++i)
    {
        if (data & 0x80)
            i2cSDALevel(1);
        else
            i2cSDALevel(0);
        
        i2cDelay();
        i2cSCLLevel(1);
        i2cDelay();

        i2cSCLLevel(0);
        i2cDelay();

        data <<= 1;
    }

    // 释放SDA
    i2cSDARelease();
}

bool i2cGetSDA()
{
    i2cSCLLevel(1);
    i2cDelay();

    bool level = gpiod_line_get_value(line_SDA);

    i2cSCLLevel(0);
    i2cDelay();

    return level;
}

u8 i2cReceive()
{
    i2cSDARelease();

    u8 data;

    for (int i = 0; i < 8; ++i)
    {
        data <<= 1;
        data |= i2cGetSDA();
    }
    
    return data;
}

u8 i2cReceiveDebug(u32* biasDebug)
{
    i2cSDARelease();

    u8 data;

    for (int i = 0; i < 8; ++i)
    {
        data <<= 1;
        data |= i2cGetSDA();
        *biasDebug <<= 2;

        // 查看pull寄存器状态
        static int dev_fd;
        unsigned char *map_base;
        dev_fd = open("/dev/mem", O_RDWR);
        map_base = (unsigned char *)mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, dev_fd, GPIO_PAGE_OFFSET);
        *biasDebug |= (*(volatile u32*)(map_base + GPIO_BASE_OFFSET + rPE_PULL0)) >> 24 & 0b11;
        munmap(map_base, MAP_SIZE);
    }
    
    return data;
}

void i2cRelease()
{
    gpiod_chip_close(gpiochip0);
}

void i2cClear()
{
    i2cSDARelease();
    for (int i = 0; i < 32; ++i)
    {
        i2cSCLLevel(0);
        i2cSCLLevel(1);
    }
}

main

void ADS1110_ReadData()
{
    if(!i2cInit())
    {
        printf("I2C init error\n");
        i2cRelease();
        exit(1);
    }

    i2cClear();

    i2cSDAConf(1);

    i2cStart();
    
    u8 addr = 0b10010001;

    i2cSend(addr);

    if (!i2cWaitAck())
    {
        printf("none ACK received\n");
        printf("%d\n", gpiod_line_direction(line_SDA));
        i2cRelease();
        exit(1);
    }

    u8 data[3];

    data[0] = i2cReceive();
    i2cACK();
    data[0] = i2cReceive();
    i2cACK();
    data[0] = i2cReceive();
    i2cNACK();

    i2cEnd();

    i2cClear();

    i2cRelease();

    printf("%x %x %x\n", data[0] & 0xFF, data[1] & 0xFF, data[2] & 0xFF);
}

同样的，使用ADS1115进行测试，也存在如上问题。