AD7768-1 no-OS Driver

See drivers/adc/ad7768-1 (doxygen) for the Doxygen documentation.

Supported Devices

AD7768-1

Overview

The AD7768-1 is a precision 24-bit analog-to-digital converter (ADC) optimized for high-performance applications in dynamic signal analysis. It offers flexible operational modes, including continuous, one-shot, single, periodic, and standby, making it adaptable to various scenarios. The converter supports SPI and pin control modes, providing functions like digital filtering, power mode adjustments, and GPIO configurations. The AD7768-1 optimizes data transfer with features such as continuous read enable, programmable finite impulse response (FIR) filters, and support for high-speed data acquisition.

Applications

Platform ADC to serve a superset of measurements and sensor types
- Sound and vibration, acoustic, and material science research and development
- Control and hardware in loop verification
- Condition monitoring for predictive maintenance
- Electrical test and measurement
- Audio testing and current and voltage measurement
- Clinical electroencephalogram (EEG), electromyogram (EMG), and electrocardiogram (ECG) vital signs monitoring
- USB-, PXI-, and Ethernet-based modular data acquisition (DAQ)
- Channel to channel isolated modular DAQ designs

Operational Modes

Driver Configuration

Initialization

To initialize the AD7768-1 device, ensure SPI communication connections and adequate power supply. Begin software setup by defining the ad77681_init_param structure for initialization parameters. This includes configuring the SPI using spi_eng_dev_init, setting power mode to AD77681_FAST, selecting master clock division as AD77681_MCLK_DIV_8, and choosing the conversion mode as AD77681_CONV_CONTINUOUS. Execute the ad77681_setup function to allocate memory for the device structures and configure the ADC operational parameters.

Power Configurations

Control the ADC power mode using ad77681_set_power_mode, selecting from AD77681_ECO, AD77681_MEDIAN, or AD77681_FAST modes. Adjust the master clock with ad77681_set_mclk_div using dividers such as AD77681_MCLK_DIV_16, AD77681_MCLK_DIV_8, AD77681_MCLK_DIV_4, and AD77681_MCLK_DIV_2.

Conversion Modes

Mode Selection for the AD7768-1 ADC involves using the ad77681_set_conv_mode function to configure the conversion mode and related settings. The available conversion modes are continuous (AD77681_CONV_CONTINUOUS), one-shot (AD77681_CONV_ONE_SHOT), single (AD77681_CONV_SINGLE), periodic (AD77681_CONV_PERIODIC), and standby. The conversion length can be defined with ad77681_set_convlen, selecting between 24-bit (AD77681_CONV_24BIT) and 16-bit (AD77681_CONV_16BIT). These configurations are written to the device’s registers via SPI.

Buffer and Reference Settings

To configure the AD7768-1 ADC input and reference buffers, use ad77681_set_AINn_buffer and ad77681_set_AINp_buffer for the negative and positive analog input precharge buffers, respectively. For managing the negative and positive reference voltages, utilize ad77681_set_REFn_buffer and ad77681_set_REFp_buffer.

Filter Configurations

The filter type for SINC filters can be set using the ad77681_set_filter_type function, while power line rejection can be enabled using the ad77681_set_50HZ_rejection function for the AD7768-1 ADC device.

Gain and Offset Adjustments

The functions ad77681_apply_gain and ad77681_apply_offset are used to calibrate the AD7768-1 ADC by writing specific 24-bit values to its gain and offset registers.

ad77681_apply_gain accepts a 24-bit gain value, splits it into three 8-bit segments (high, middle, and low), and writes each to the GAIN_HI, GAIN_MID, and GAIN_LO registers using SPI communication. Similarly, ad77681_apply_offset configures the offset setting by dividing a 24-bit offset value into high, middle, and low bytes, then writing them to the OFFSET_HI, OFFSET_MID, and OFFSET_LO registers via SPI. Both functions return 0 on successful execution or a negative error code if any SPI write operations fail.

Note: When configuring the AD7768-1 device, verify that all configuration values are consistent with the specific platform or hardware in use, especially regarding clock speeds, power modes, and SPI settings. Accurate device-specific configurations are crucial to avoid performance or compatibility issues.

Driver Initialization Example

#include "ad77681.h"
#include "no_os_spi.h"

// Driver Initialization Code for AD7768-1 ADC

struct ad77681_init_param ADC_default_init_param = {
    /* SPI Configuration */
    .spi_eng_dev_init = {
        .chip_select = AD77681_SPI_CS,       // Chip select configuration
        .max_speed_hz = 1000000,            // Max speed of SPI in Hz
        .mode = NO_OS_SPI_MODE_3,           // SPI mode 3
        .platform_ops = &spi_eng_platform_ops,
        .extra = (void*)&spi_eng_init_param // Additional configuration parameters
    },
    /* ADC Configuration */
    .power_mode = AD77681_FAST,              // High-speed power mode
    .mclk_div = AD77681_MCLK_DIV_8,          // Master clock division
    .conv_mode = AD77681_CONV_CONTINUOUS,    // Continuous conversion mode
    .diag_mux_sel = AD77681_POSITIVE_FS,     // Diagnostic mux selection
    .conv_diag_sel = false,                  // Conversion diagnostics disabled
    .conv_len = AD77681_CONV_16BIT,          // Conversion bit length
    .crc_sel = AD77681_CRC,                  // CRC data integrity check enabled
    .status_bit = 0,                         // Default status
    .vcmo = AD77681_VCM_HALF_VCC,            // VCM configuration
    .ainn_buf = AD77681_AINn_ENABLED,        // Negative input precharge buffer enabled
    .ainp_buf = AD77681_AINp_ENABLED,        // Positive input precharge buffer enabled
    .refn_buf = AD77681_BUFn_ENABLED,        // REF- buffer enabled
    .refp_buf = AD77681_BUFp_ENABLED,        // REF+ buffer enabled
    .fir_filter = AD77681_FIR,               // FIR filter configuration
    .dec_rate = AD77681_SINC5_FIR_DECx32,    // Decimation rate
    .sinc3_osr = 0,                         // Oversampling rate of SINC3
    .ref_voltage = 4096,                     // Reference voltage in mV
    .mclk_freq = 16384                       // MCLK frequency in kHz

};

// Function to initialize the AD7768-1 device
int main()
{
    struct ad77681_dev *adc_dev;
    struct ad77681_status_registers *adc_status;
    uint8_t adc_data[5];
    int32_t ret;

    // Perform setup using the predefined initialization parameters
    ret = ad77681_setup(&adc_dev, &ADC_default_init_param, &adc_status);
    if (ret != 0) {
        printf("AD7768-1 ADC device setup failed\n");
        return -1;
    }

    // Enter continuous data reading loop
    while (1) {
        ad77681_spi_read_adc_data(adc_dev, adc_data, AD77681_CONTINUOUS_DATA_READ);
        printf("[ADC DATA]: 0x");
        for (int i = 0; i < sizeof(adc_data); i++) {
            printf("%02x", adc_data[i]);
        }
        printf("\n");
        no_os_mdelay(1000);  // Delay for 1 second
    }

    return 0;
}