AD7768-1 no-OS Example Project

See projects/ad7768-1fmcz (doxygen) for the Doxygen documentation.

Supported Evaluation Boards

Overview

The EV-AD77681FMCZ evaluation kit contains the AD7768-1, a 24-bit, 256 kSPS precision sigma-delta ADC with an integrated PGA and on-chip reference buffer. The device achieves 108 dB dynamic range and offers three power modes (fast, median, and low power), making it well suited for sensor measurement systems that require both high accuracy and flexible power consumption. A 4-wire SPI interface provides register access for configuring the input range, power mode, and data formatting.

The evaluation board plugs into a Xilinx carrier board (such as the ZedBoard) via the FMC LPC connector. An AXI SPI Engine core on the FPGA manages SPI communication, and an AXI clock generator provides the master clock to the ADC.

Applications

  • Sound and vibration, acoustic, and materials science research

  • Control and hardware-in-the-loop verification

  • Condition monitoring for predictive maintenance

  • Electrical test and measurement

  • Audio testing, current and voltage measurement

  • Clinical EEG, EMG, and ECG vital-signs monitoring

  • USB-, PXI-, and Ethernet-based modular DAQ

  • Channel-to-channel isolated modular DAQ designs

Hardware Specifications

Power Supply Requirements

The EV-AD77681FMCZ is powered from the carrier board via the FMC connector. Set the VINSEL jumper to Position B to derive power from the EVAL-SDP-CH1Z (5 V and 3.3 V). On-board linear regulators (U8, U9, U10) provide 5 V and 7 V; ADP1718 and ADP7118 generate 3.3 V and 10 V. AD840/AD841 reference amplifiers stabilize operating conditions.

On-board Connectors

Connector

Function

Description

SMB Connectors

AIN1+, AIN1-

Main differential analog input channels

Terminal Blocks

Additional Inputs

Alternative access points for analog signals

J4 (FMC LPC)

Carrier Connection

Connects to the carrier board (e.g. ZedBoard)

P1 Socket

Primary Interface

Main connection socket for external connections

No-OS Supported Examples

This project is organized around the no-OS variant-based build flow. Selecting a variant at build time (--variant <name>) chooses which application is compiled. Shared initialization data is defined in src.

Demo Example

The demo example initializes the AD7768-1 ADC using the AXI SPI Engine core and the AXI clock generator. It then reads conversion results continuously in standard (non-offload) SPI Engine mode and prints them over UART.

SPI Engine Offload Example

The SPI Engine offload example configures the AXI SPI Engine in offload mode with DMA to capture a burst of samples from the AD7768-1 into DDR memory and prints the raw results over UART.

No-OS Supported Platforms

Xilinx

Used Hardware

Connections

The EV-AD77681FMCZ plugs into the ZedBoard via the FMC LPC connector. The SPI Engine core on the Zynq PL manages the SPI bus (SPI_CLK, SPI_MISO, SPI_MOSI, SPI_CS) routed through the FMC connector. Connect a USB-to-serial cable to the ZedBoard UART (J14, 115200 baud) to view output.

Signal

Description

ZedBoard MIO Pin

EV-AD77681FMCZ Pin

SPI_CLK

Serial Clock

P16

P6

SPI_MISO

Master In Slave Out

P17

P5

SPI_MOSI

Master Out Slave In

P21

P4

SPI_CS

Chip Select

P1

P3

Build Command

The Xilinx platform uses the CMake/Ninja build system via the no_os_build.py helper script. Available variants: demo, spi_engine_offload. Available boards: zed.

For toolchain setup and prerequisites, see the Xilinx CMake build guide.

# Source the Vitis environment (adjust path for your installation):
source ~/.xilinx/2025.1/Vitis/settings64.sh
# PowerShell (Windows) equivalent:
#   & "$env:XILINX_VITIS\settings64.bat"

cd no-OS

# Build the demo example on zed
python tools/scripts/no_os_build.py build \
   --project ad7768-1fmcz --variant demo --board zed \
   --hardware /path/to/ad77681evb_zed/system_top.xsa

# Build the SPI Engine offload example on zed
python tools/scripts/no_os_build.py build \
   --project ad7768-1fmcz --variant spi_engine_offload --board zed \
   --hardware /path/to/ad77681evb_zed/system_top.xsa

# Build and flash (requires a connected debug probe)
python tools/scripts/no_os_build.py build \
   --project ad7768-1fmcz --variant demo --board zed \
   --hardware /path/to/ad77681evb_zed/system_top.xsa \
   --probe openocd --flash