[参考译文] ADS7142：手动模式双通道读取返回0x00 -需要有关正确配置和示例代码的帮助

https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/1407396/ads7142-manual-mode-dual-channel-read-returns-0x00---need-help-with-correct-configuration-and-sample-code

工具与软件：

我使用的是 ADS7142 ADC、并尝试在手动模式、双通道单端配置中从两个通道读取数据。 与芯片的通信正常、而且我能够写入和读取寄存器。 但是、我尝试读取 ADC 转换数据时、该数据始终0x00针对两个通道返回。

我认为错误是由于对寄存器配置和寄存器值的解释误解造成的。

这是我使用的寄存器

#define OPMODE_SEL_REG 0x1C
#define AUTO_SEQ_CHEN_REG 0x20
#define START_SEQUENCE_REG 0x1E
#define SEQUENCE_STATUS_REG 0x04
#define ABORT_SEQUENCE_REG 0x1F
#define DOUT_FORMAT_CFG_REG 0x28
#define CHANNEL_INPUT_CFG_REG 0x24
#define CONVERSION_RESULT_REG 0x00  

这是我用于读取和写入寄存器的函数

// Function to write to a register
int write_register(int file, int reg, int value) {
    char data[3] = {0x08, reg, value};  // Opcode 0x08 for single register write
    if (write(file, data, 3) != 3) {
        perror("Failed to write to the i2c bus");
        return -1;
    }
    usleep(100000);  // Wait 100ms after write operation
    return 0;
}

// Function to read data from a register
int read_register(int file, int reg, int read_len) {
    char cmd[2] = {0x10, reg}; // Opcode 0x10 for single register read
    if (write(file, cmd, 2) != 2) {
        perror("Failed to write to the i2c bus for read");
        return -1;
    }
    usleep(100000);  // Wait 100ms after setting register

    char data[read_len];
    if (read(file, data, read_len) != read_len) {  // Read specified bytes
        perror("Failed to read from the i2c bus");
        return -1;
    }

    int result = 0;
    for (int i = 0; i < read_len; i++) {
        result = (result << 8) | data[i];  // Combine MSB and LSB
    }
    return result;
}

以下是我尝试读取两个通道值的序列：

int main() {
    int file;
    char filename[20];

    snprintf(filename, 19, I2C_DEVICE);

    // Open the I2C device
    if ((file = open(filename, O_RDWR)) < 0) {
        perror("Failed to open the i2c bus");
        exit(1);
    }

    // Specify the address of the I2C device
    if (ioctl(file, I2C_SLAVE, ADS7142_ADDRESS) < 0) {
        perror("Failed to acquire bus access and/or talk to slave");
        close(file);
        exit(1);
    }

    // Step 1: Verify auto-sequence enabled by reading AUTO_SEQ_CHEN register (Addr: 0x20)
    int auto_seq = read_register(file, AUTO_SEQ_CHEN_REG, 1);
    if (auto_seq != 0x03) {  // Both CH0 and CH1 should be enabled
        printf("Auto-sequence not enabled properly: 0x%02x\n", auto_seq);
        close(file);
        exit(1);
    }

    // Step 2: Configure Two-Channel Single-Ended Input (Addr: 0x24)
    write_register(file, CHANNEL_INPUT_CFG_REG, 0x00);  // Set for 2-channel, single-ended

    // Step 3: Set OPMODE_SEL to Manual Mode with Auto Sequence enabled (Addr: 0x1C)
    write_register(file, OPMODE_SEL_REG, 0x04);  // Manual mode with auto sequence

    // Step 4: Confirm OPMODE_SEL is set correctly by reading (Addr: 0x1C)
    int opmode_status = read_register(file, OPMODE_SEL_REG, 1);
    printf("OPMODE_SEL Register: 0x%02x\n", opmode_status);

    if (opmode_status != 0x04) {
        printf("Failed to set manual mode with auto sequence. Current mode: 0x%02x\n", opmode_status);
        close(file);
        exit(1);
    }

    // Step 5: Read SEQUENCE_STATUS Register (Addr: 0x04) to verify Auto Seq enabled
    int seq_status = read_register(file, SEQUENCE_STATUS_REG, 1);
    printf("SEQUENCE_STATUS Register: 0x%02x\n", seq_status);

    if (seq_status != 0x02) {
        printf("Auto sequence is not enabled. Current status: 0x%02x\n", seq_status);
        close(file);
        exit(1);
    }

    // Step 6: Set DOUT_FORMAT_CFG to provide at least CHID (Addr: 0x28)
    write_register(file, DOUT_FORMAT_CFG_REG, 0x01);  // Configure data output format

    // Step 7: Start the conversion sequence (Addr: 0x1E)
    write_register(file, START_SEQUENCE_REG, 0x01);

    // Step 8: Read conversion results continuously
    int read_count = 0;
    while (read_count < 20) {  // Read continuously for 20 iterations (adjust as needed)
        usleep(200000);  // Wait 200ms before reading to allow conversion to complete
        int result = read_register(file, CONVERSION_RESULT_REG, 4);  // Read 4 bytes
        printf("ADC Result: 0x%08x\n", result);
        read_count++;
    }

    // Step 9: Stop the conversion sequence (Addr: 0x1F)
    write_register(file, ABORT_SEQUENCE_REG, 0x01);

    // Close the I2C device
    close(file);

    return 0;
}

输出只是0、不知道原因是什么：

OPMODE_SEL 寄存器：0x04
SEQUENCE_STATUS 寄存器：0x02
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000
ADC 结果：0x00000000