AD9625 no-OS Driver

Supported Devices

• AD9625

Overview

The AD9625 is a 12-bit monolithic analog-to-digital converter (ADC) optimized for high-speed applications with sampling rates up to 2.6GSPS. It supports wide bandwidth analog signals up to the second Nyquist zone, making it suitable for spectrum analyzers, radar, and electronic countermeasures. The ADC provides differential inputs for analog, clock, and synchronous signals, with JESD204B-based outputs configurable across one to eight lanes. Operating over a temperature range of -40°C to +85°C, it ensures excellent linearity and performance in demanding environments.

Applications

• Spectrum analyzers

• Military communications

• Radar systems

• High performance digital storage oscilloscopes

• Active jamming/anti-jamming

• Electronic surveillance and countermeasures

Operation Modes

Mode Name	Description	Config Bits	Typical Use Case
AD9625_TEST_OFF	No test mode is active	0x000	Normal ADC operation without test patterns
AD9625_TEST_MID_SCALE	Mid-scale input test pattern	0x001	Testing mid-scale linearity
AD9625_TEST_POS_FSCALE	Positive full-scale input test pattern	0x002	Testing positive full-scale response
AD9625_TEST_NEG_FSCALE	Negative full-scale input test pattern	0x003	Testing negative full-scale response
AD9625_TEST_CHECKBOARD	Alternating checkerboard pattern	0x004	Testing data integrity with alternating pattern
AD9625_TEST_PNLONG	Long pattern sequence	0x005	Comprehensive long sequence test for pattern integrity
AD9625_TEST_ONE2ZERO	Alternating 1 to 0 test pattern	0x007	Testing alternating toggle response
AD9625_TEST_PATTERN	Custom test pattern	0x008	Testing user-defined patterns
AD9625_TEST_RAMP	Ramp test pattern	0x00F	Testing linearity across full range

Device Configuration

Device Setup and Configuration

The ad9625_setup function initializes and configures the AD9625, involving memory allocation, SPI initialization, and register configuration. Verification steps check the chip ID and PLL lock status to ensure proper ADC configuration.

Resource Management

The ad9625_remove function deallocates resources associated with the AD9625, removing the SPI descriptor and freeing allocated memory to ensure proper resource release.

SPI Communication

The ad9625_spi_read and ad9625_spi_write functions handle SPI interactions for the AD9625. The read function constructs a command to fetch data from a register, while the write function sends a command to write a byte of data to a register.

Testing and Validation

The ad9625_test function configures the ADC for various operational tests using a ‘test_mode’ parameter, setting the ADC’s test control register accordingly. This allows for performance verification under different conditions, ensuring the ADC operates correctly across various setups.

Driver Initialization Example

#include <stdint.h>
#include "no_os_delay.h"
#include "no_os_spi.h"

// Initialization parameters for the AD9625 device
struct ad9625_init_param {
    struct no_os_spi_init_param spi_init; // SPI configuration
    uint32_t lane_rate_kbps; // Lane rate in kbps
    uint32_t test_samples[4]; // Test samples
};

// Device structure for the AD9625
struct ad9625_dev {
    struct no_os_spi_desc *spi_desc; // SPI descriptor
};

// Set up the AD9625 device
int32_t ad9625_setup(struct ad9625_dev **device, struct ad9625_init_param init_param) {
    struct ad9625_dev *dev;
    int32_t ret;
    uint8_t chip_id;
    uint8_t pll_stat;

    // Memory allocation and SPI initialization
    dev = (struct ad9625_dev *)no_os_malloc(sizeof(*dev));
    ret = no_os_spi_init(&dev->spi_desc, &init_param.spi_init);
    if (ret < 0) {
        no_os_free(dev);
        return ret;
    }

    // Device register configuration
    ad9625_spi_write(dev, AD9625_REG_CHIP_PORT_CONF, 0x00);
    ad9625_spi_write(dev, AD9625_REG_OUTPUT_MODE, 0x01);
    ad9625_spi_write(dev, AD9625_REG_OUTPUT_ADJUST, 0x10);
    ad9625_spi_write(dev, AD9625_REG_JESD204B_LINK_CNTRL_1, 0x14);
    ad9625_spi_write(dev, AD9625_REG_TRANSFER, 0x01);
    no_os_mdelay(10);

    // Check chip ID and PLL status
    ad9625_spi_read(dev, AD9625_REG_CHIP_ID, &chip_id);
    if (chip_id != AD9625_CHIP_ID) {
        printf("%s Error: Invalid CHIP ID (0x%x).\n", __func__, chip_id);
        return -1;
    }
    ad9625_spi_read(dev, AD9625_REG_PLL_STATUS, &pll_stat);
    if ((pll_stat & 0x80) != 0x80) {
        printf("%s Error: AD9625 PLL is NOT locked (0x%x).\n", __func__, chip_id);
        return -1;
    }

    *device = dev;
    return ret;
}

// Main function for AD9625 initialization
int main() {
    struct ad9625_dev *ad9625_device;
    struct ad9625_init_param init_param = {
        .spi_init = {/* SPI initialization parameters */},
        .lane_rate_kbps = 20000, // Example lane rate
        .test_samples = {0, 1, 2, 3} // Example test samples
    };

    int32_t status = ad9625_setup(&ad9625_device, init_param);
    if (status == 0) {
        printf("AD9625 setup successfully.\n");
    } else {
        printf("AD9625 setup failed with status %d.\n", status);
    }

    // Further application logic
    return 0;
}