The AD5628 The AD5628 is a low power, octal, 12 bit, buffered voltage-output DAC. The device operates from a single 2.7 V to 5.5 V supply and is guaranteed monotonic by design. The AD5628 is available in both a 4 mm × 4 mm LFCSP and a 16-lead TSSOP. The AD5628 has an on-chip reference with an internal gain of 2. The AD5628 has a 1.25 V 5 ppm/°C reference, giving a full-scale output range of 2.5 V; the AD5628-2 has a 2.5 V 5 ppm/°C reference, giving a full-scale output range of 5 V. The on-board reference is off at power-up, allowing the use of an external reference. The internal reference is enabled via a software write.

HW Platform(s):

• Spartan-6 LX9 Microboard (Avnet)
• Nexys?3 Spartan-6 FPGA Board (Digilent)
• Avnet ZedBoard
  

The bit file provided in the project *.zip file combines the FPGA bit file and the SDK elf files. It may be used for a quick check on the system. All you need is the hardware and a PC running a UART terminal and the programmer (IMPACT).

• Spartan-6 LX9 Microboard (Avnet)
• Nexys?3 Spartan-6 FPGA Board (Digilent)
• Avnet ZedBoard
• PmodDA4 (Digilent)

• Xilinx ISE 14.4 (Programmer (IMPACT) is sufficient for the demo and is available on Webpack).
• A UART terminal (Tera Term/Hyperterminal), Baud rate 115200 for the Avnet LX-9 Microboard and ZedBoard or 9600 for the Digilent Nexys?3 Board.

Extract the project from the archive file (AD5628_.zip) to the location you desire.

To begin, connect the PmodDA4 to J4 connector of LX9 board, pins 1 to 6 (see image below). You can use an extension cable for ease of use. Connect the USB cable from the PC to the USB-UART female connector of the board for the UART terminal. The board will be programmed through its USB male connector.

Extract the project from the archive file (AD5628_.zip) to the location you desire.

To begin, connect the PmodDA4 to JB connector of Nexys?3 board, pins JB1 to JB6 (see image below). You can use an extension cable for ease of use. Connect the USB cables from the PC to the board, one for programming (Digilent USB device) and one for the UART terminal (FT232R USB UART).

To begin, connect the PmodDA4 to JA1 connector of ZedBoard (see image below). You can use an extension cable for ease of use. Connect the USB cables from the PC to the board, one for programming (Digilent USB device) and one for the UART terminal (FT232R USB UART).

Start IMPACT, and double click “Boundary Scan”. Right click and select Initialize Chain. The program should recognize the Spartan 6 device (see screenshot below). Connect an oscilloscope to the following outputs of PmodDA4: A,C,E,G. Program the device using the bit file provided in the project *.zip archive, located in the “sw” folder (../ad5628/sw/AD5628.bit).

Run the download.bat script from the “../bin” folder downloaded from the github (see the links in the download section of the wiki page). The script will automatically configure the ZYNQ SoC and download the *.elf file afterwards.

If programming was successful, the Main Menu will apear in your UART terminal, as seen in the picture below. There are 3 options:

• Press [f] to select Fixed Value Mode.
• Press [w] to select Waveform Generation Mode.
• Press [p] to select Programmable Ramp Signal Generator.

When entering Fixed Value Mode, DAC selection is automatically activated. Selecting the DAC is done by pressing [1] to [9].

Fixed Value Mode allows entering a value between 0x000 and 0xFFF, value that will be programmed in the DAC. If the number of input characters is less than 3 (e.g. ff or 76), the [Enter] key must be pressed in order to validate the input. If 3 characters are input, the value is automatically validated (in order to prevent entering more than 3 characters). Pressing the [s] key at any time will enter DAC Selection Mode.

Pressing the [q] key at any time exits the Fixed Value (or Waveform Generation) Mode and displays the Main Menu again.

When entering Waveform Generation Mode, DAC selection is automatically activated. Selecting the DAC is done by pressing [1] to [9].

Waveform Generation Mode allows selecting between 4 types of waveforms: Square, Triangle, Sawtooth and Sine waveforms. Changing between the 4 is done by pressing [1] to [4] on the keyboard. Pressing [s] at any time will enter DAC Selection Mode. Pressing [q] at any time will return to the Main Menu.

Programmable Ramp Signal Generator allows generating a programmable ramp signal. This mode can be used to test the PmodDA4 using a Digital Multimeter.

Enter time step allows setting a time step between 100 and 5000 ms.

Enter increment size allows selecting an increment size that suits your design. Values can vary from 0x000 to 0xFFF.

Select DAC allows selecting which DAC Output will be used for the Ramp Signal Generation.

Run Ramp Signal Generator will start generating the desired output.

The reference design is a simple SPI interface used to communicate with the PmodDA4. The software programs the device sending 12-bit data values read from the keyboard input or from predefined look up tables. The user has the ability to select between two modes: a Fixed Value Mode or a Waveform Generation Mode. Communication between the user and the board is done via UART.

// Select between PS7 or AXI Interface
#define USE_PS7 	 1
// SPI used in the design
#define USE_SPI		 1
// I2C used in the design
#define USE_I2C		 0
// Timer (+interrupts) used in the design
#define USE_TIMER	 1
// External interrupts used in the design
#define USE_EXTERNAL     0
// GPIO used in the design
#define USE_GPIO         0

====== Linux Device Driver ====== Connect PmodDA4 to the JB1 connector of the ZedBoard (upper row of pins). ===== Preparing the SD Card ===== In order to prepare the SD Card for booting Linux on the ZedBoard: * Download the device tree: PmodDA4 Linux devicetree * Follow the instructions on the following wiki page, but use the device tree downloaded on the previous step * Linux with HDMI video output on the ZED and ZC702. Make sure you have an HDMI monitor connected to the ZedBoard, plug in the SD Card and power on the board. If everything is correct, the system should boot up. If you don't have an HDMI monitor, connect to the board via UART, Baud Rate 115200. There are 2 ways to test the driver. * Using the terminal window * Using a serial terminal ===== Using the terminal window ===== Open a new terminal window by pressing Ctrl+Alt+T. Navigate to the location of the device and identify it using the following commands: cd /sys/bus/iio/devices/ ls iio:device0 iio:device1 trigger0 cd iio/:device0 cat name ad5628-1 If the cat name command doesn't return ad5628-1, then change the number of the iio:device, and check again. cd .. cd iio/:device1 cat name To see the list of options that the AD5628 driver provides, type: ls dev out_voltage4_powerdown_mode name out_voltage4_raw out_voltage0_powerdown out_voltage4_scale out_voltage0_powerdown_mode out_voltage5_powerdown out_voltage0_raw out_voltage5_powerdown_mode out_voltage0_scale out_voltage5_raw out_voltage1_powerdown out_voltage5_scale out_voltage1_powerdown_mode out_voltage6_powerdown out_voltage1_raw out_voltage6_powerdown_mode out_voltage1_scale out_voltage6_raw out_voltage2_powerdown out_voltage6_scale out_voltage2_powerdown_mode out_voltage7_powerdown out_voltage2_raw out_voltage7_powerdown_mode out_voltage2_scale out_voltage7_raw out_voltage3_powerdown out_voltage7_scale out_voltage3_powerdown_mode out_voltage_powerdown_mode_available out_voltage3_raw power out_voltage3_scale subsystem out_voltage4_powerdown uevent To set the raw output voltage for channel A, type: echo 1200 > out_voltage0_raw To check that the raw output voltage has been set, you can type: cat out_voltage0_raw 1200 If you want to set the voltage for another channel, replace out_voltage0_raw with, for example, out_voltage1_raw. The commands written above can also be used if not using an HDMI monitor and a wireless keyboard, by using a serial terminal, and typing the commands after the system boot-up is complete.

• ask questions about the FPGA reference design
• Example questions:

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