Digilent Cmod A7-35T Artix-7 FPGA Module User Manual

1. Introduction

The Digilent Cmod A7-35T is a compact, breadboard-friendly Field-Programmable Gate Array (FPGA) module designed for digital logic circuits and MicroBlaze embedded soft-core processor designs. Built around a Xilinx Artix-7 FPGA, this module integrates essential components such as a USB-JTAG programming circuit, USB-UART bridge, clock source, Pmod host connector, SRAM, Quad-SPI Flash, and basic I/O devices. Its small 48-pin DIP form factor allows for direct integration into solderless breadboard circuits, making it an ideal platform for both educational and prototyping applications.

This manual provides essential information for setting up, operating, and maintaining your Cmod A7-35T module, along with technical specifications and troubleshooting tips.

2. Key Features

• FPGA: Xilinx Artix-7 XC7A35T-1CPG236C with 20,800 Look-up Tables (LUTs) and 41,600 Flip-flops.
• Form Factor: Small, breadboard-friendly 48-pin DIP.
• Programming: USB-JTAG programming circuit and Quad-SPI Flash.
• Communication: USB-UART bridge.
• Memory: SRAM and Quad-SPI Flash.
• I/O: 44 Digital FPGA I/O signals, two FPGA Analog inputs routed to 100-mil-spaced through-hole pins.
• On-board Peripherals: 2 LEDs, 1 RGB LED, and 2 push buttons.
• Expansion: One Pmod connector with 8 Digital I/O.
• Software Support: Compatible with Xilinx Vivado Design Suite (WebPACK Edition).

3. Setup Guide

Follow these steps to set up your Digilent Cmod A7-35T module:

1. Software Installation: Download and install the Xilinx Vivado Design Suite (WebPACK Edition) from the official Xilinx website. This software is essential for designing, synthesizing, and programming your FPGA.
2. Driver Installation: Ensure that the necessary USB-JTAG and USB-UART drivers are installed on your computer. These are typically included with the Vivado installation or can be found on the Digilent support website.
3. Physical Connection: Insert the Cmod A7-35T into a standard solderless breadboard or a compatible socket. Ensure all pins are correctly seated.
4. Power Connection: Connect the Cmod A7-35T to your computer using a USB cable. The module will draw power and establish a communication link via the USB-UART bridge and USB-JTAG programming circuit.
5. First Project: Refer to Digilent's official documentation and tutorials for your first project. These resources provide step-by-step guides for creating and loading a basic design onto the FPGA.

Figure 1: Top view of the Cmod A7-35T module, highlighting the USB connector and main components.

4. Operating Instructions

The Cmod A7-35T is primarily operated through the Xilinx Vivado Design Suite. Here are general guidelines for its use:

1. Design Creation: Use Vivado to create your digital logic designs (e.g., VHDL or Verilog) or MicroBlaze embedded processor projects.
2. Synthesis and Implementation: Compile your design in Vivado. This process translates your code into a configuration file (bitstream) for the FPGA.
3. Programming the FPGA: Connect the Cmod A7-35T via USB. Use the Vivado Hardware Manager to detect the device and load your generated bitstream onto the Artix-7 FPGA. The Quad-SPI Flash can be used for non-volatile storage of your configuration.
4. Interacting with I/O: Utilize the 44 digital I/O pins and two analog inputs for connecting external circuits. The on-board LEDs and push buttons provide immediate feedback and input capabilities for simple designs.
5. Pmod Expansion: The Pmod connector allows for easy integration with Digilent Pmod peripheral modules, expanding the functionality of your Cmod A7-35T.
6. USB-UART Communication: Use the USB-UART bridge for serial communication between your computer and your FPGA design, useful for debugging and data transfer.

Figure 2: Bottom view of the Cmod A7-35T module, illustrating the pin layout for breadboard integration.

5. Specifications

6. Maintenance

To ensure the longevity and reliable operation of your Cmod A7-35T module, observe the following maintenance guidelines:

• Handling: Always handle the module by its edges to avoid touching the sensitive electronic components. Static electricity can damage the device, so use appropriate ESD (Electrostatic Discharge) precautions.
• Storage: Store the module in a dry, cool environment, away from direct sunlight and extreme temperatures. Keep it in its original anti-static packaging when not in use.
• Cleaning: If necessary, gently clean the board with a soft, dry brush or compressed air to remove dust. Avoid using liquids or abrasive cleaners.
• Power Supply: Ensure that the USB power source provides stable and clean power. Avoid using uncertified or damaged USB cables.

7. Troubleshooting

If you encounter issues with your Cmod A7-35T, consider the following troubleshooting steps:

• Module Not Detected by Vivado:
  • Verify that the USB cable is securely connected to both the module and your computer.
  • Ensure that the necessary USB-JTAG drivers are correctly installed. Check your device manager for any unrecognized devices.
  • Try a different USB port or a different USB cable.
  • Restart Vivado and/or your computer.
• Intermittent USB-UART Communication Loss:
  • This issue can sometimes be resolved by using a high-quality, USB-certified cable. Some cables may not provide sufficient power stability or data integrity for continuous operation.
  • Try disconnecting and reconnecting the USB cable, or power cycling the board.
  • Ensure your computer's USB ports are providing adequate power.
• Design Not Functioning as Expected:
  • Double-check your VHDL/Verilog code for logical errors.
  • Review your pin assignments (XDC constraints) in Vivado to ensure they match the Cmod A7-35T's physical I/O.
  • Use Vivado's simulation tools to verify your design's behavior before programming the FPGA.
  • Consult Digilent's online forums and documentation for common design pitfalls and solutions.

8. Support and Resources

For further assistance, detailed tutorials, and community support, please refer to the official Digilent resources:

• Digilent Website: Visit digilent.com for product documentation, downloads, and support.
• Resource Center: Explore the Digilent Resource Center for comprehensive guides, example projects, and technical articles related to the Cmod A7-35T and Xilinx FPGAs.
• Community Forum: Engage with other users and Digilent engineers on the official Digilent Forum for questions and discussions.

While specific warranty details are not provided in this manual, Digilent typically offers product warranties. Please check their official website for the most current warranty information and return policies.