Introduction

In the world of DIY electronics, programmable logic devices (PLDs) offer a versatile and dynamic platform for enthusiasts looking to dive into digital design and hardware programming. One such PLD is the EPM7192SQC160-15, a Complex Programmable Logic Device (CPLD) from the MAX 7000 series by Altera (now part of Intel). This CPLD is an excellent choice for building your own development board or experimenting with digital circuits, offering a balance of functionality and complexity suitable for intermediate to advanced DIY electronic hobbyists. In this article, we’ll walk through the process of designing and building a CPLD development board using the EPM7192SQC160-15, exploring its features, pin configuration, and project implementation.

Understanding the EPM7192SQC160-15

The EPM7192SQC160-15 is part of the Altera MAX 7000 series of CPLDs, which are non-volatile programmable devices capable of implementing a wide range of digital logic functions. This specific model comes in a 160-pin SQFP (Square Quad Flat Package) configuration, providing ample I/O pins and flexibility for designing custom digital logic circuits. Here are some of its key features:

1. 192 Macrocells: The EPM7192SQC160-15 has 192 macrocells, which are the basic building blocks for implementing logic functions. These macrocells allow for complex logic designs, including state machines, counters, and more.

2. Non-Volatile: The CPLD retains its programmed state even after power is removed, making it reliable for applications that require consistent behavior.

3. High-Speed Operation: With a maximum speed grade of 15 ns, this CPLD can handle high-speed digital applications.

4. Flexible I/O Configuration: The 160-pin configuration provides plenty of input/output pins, which can be programmed to suit various applications.

Project Overview

In this project, we’ll build a basic development board around the EPM7192SQC160-15. This board will allow you to program and test digital designs easily. The development board will feature:

· Power regulation circuit for stable power supply to the CPLD.

· JTAG programming interface for loading the CPLD configuration.

· Clock generation circuit for providing the CPLD with a timing reference.

· Breakout pins for easy access to the I/O pins of the CPLD.

· Test LED indicators for debugging and monitoring the CPLD's output.

Required Components

1. EPM7192SQC160-15 CPLD: The core component of the project.

2. Voltage Regulators: To provide 3.3V and 5V power rails. LDO regulators like the LM1117-3.3 and LM7805 are suitable options.

3. Capacitors and Resistors: For power smoothing and filtering.

4. Crystal Oscillator: A 50 MHz oscillator is recommended for providing a clock signal to the CPLD.

5. JTAG Header: For programming the CPLD using a USB Blaster or similar programmer.

6. LEDs and Resistors: For visual feedback and testing.

7. Miscellaneous Components: Headers, connectors, and a PCB or protoboard for assembly.

Step 1: Schematic Design

Before starting with the physical construction, it’s crucial to design the schematic of the development board. A schematic allows you to visualize how components will be connected and ensures that all connections are logically correct before proceeding to the physical assembly. Below is an outline of the schematic:

1. Power Circuit:

•  The board will need two voltage levels: 3.3V for the CPLD and 5V for other peripheral components.

•  Use the LM7805 to step down the input voltage (from a 9V power source or USB) to 5V.

•  Use the LM1117-3.3 to further regulate the 5V down to 3.3V for the CPLD.

•  Add capacitors (e.g., 10 µF and 0.1 µF) across the input and output of the regulators to reduce noise.

2. JTAG Interface:

•  The JTAG header will consist of four essential pins: TDI (Test Data In), TDO (Test Data Out), TCK (Test Clock), and TMS (Test Mode Select). These are connected to the corresponding pins on the CPLD for programming and debugging.

•  Connect a pull-up resistor (typically 4.7kΩ) to the TCK line to ensure stable clock input during programming.

3. Clock Circuit:

•  Connect the crystal oscillator to the clock input pins of the EPM7192SQC160-15.

•  Ensure proper decoupling with capacitors (e.g., 22 pF) on each side of the crystal to stabilize oscillation.

4. Breakout Pins:

•  Route the I/O pins of the CPLD to a set of headers. This will allow you to connect external components like switches, sensors, or LEDs for testing purposes.

Step 2: PCB Design and Assembly

Once the schematic is complete, the next step is to design the PCB layout. You can use software like KiCad or Eagle to create the PCB design. Pay attention to the following details:

1. Component Placement: Place the EPM7192SQC160-15 in the center of the PCB with ample space around it for routing the breakout pins. Ensure the power regulation components are grouped together for a clean power rail design.

2. Routing Traces: Ensure that the power and ground traces are thick enough to handle current. Keep signal traces short and avoid crossing them over power lines to minimize interference.

3. Decoupling Capacitors: Place small capacitors (0.1 µF) close to the power pins of the CPLD to filter high-frequency noise.

After designing the PCB, you can either etch your own PCB using the toner transfer method or have it fabricated through a PCB manufacturing service. Once the PCB is ready, solder the components carefully, starting with smaller components like resistors and capacitors, then moving to larger ones like the voltage regulators and the CPLD.

Step 3: Programming the CPLD

To program the EPM7192SQC160-15, you’ll need a JTAG programmer such as Altera’s USB Blaster. The programming process involves the following steps:

1. Install Software: Install the Quartus Prime software from Intel, which supports programming and configuring Altera CPLDs and FPGAs.

2. Create a Project: In Quartus Prime, create a new project and select the EPM7192SQC160-15 as the target device.

3. Design and Compile: Write your logic design using VHDL or Verilog. Once your design is complete, compile it in Quartus Prime to generate the programming file (usually in .pof format for CPLDs).

4. Program the CPLD: Connect the USB Blaster to the JTAG header on your board and program the CPLD using the .pof file. Verify the programming process through the Quartus Prime software.

Step 4: Testing and Debugging

With the CPLD programmed, it’s time to test your development board. Here are some simple tests and troubleshooting tips:

1. Power Test: Ensure the board powers up correctly. Check that the voltage levels are as expected (3.3V and 5V) using a multimeter.

2. Clock Verification: Confirm that the crystal oscillator is providing a clock signal to the CPLD using an oscilloscope.

3. JTAG Test: Verify that the JTAG interface is functioning correctly. If Quartus Prime does not detect the CPLD, check the connections and ensure the pull-up resistor is properly placed.

4. LED Test: Program a simple LED blinking logic into the CPLD. Connect an LED and resistor to one of the breakout pins, and verify if the LED blinks as expected.

Applications and Further Development

With the development board built, you can implement various projects and digital circuits. Some examples include:

· Counters and Timers: Use the CPLD to create complex counters and timers with custom clock dividers.

· State Machines: Design finite state machines (FSMs) for controlling robotic movements, motor drivers, or automation systems.

· PWM Controllers: Implement pulse-width modulation (PWM) for controlling the brightness of LEDs or the speed of DC motors.

· Communication Protocols: Design and test digital communication interfaces such as SPI, I2C, or UART using the CPLD.

Conclusion

Building a development board around the EPM7192SQC160-15 is an excellent way to explore the world of programmable logic devices. This project provides a foundation for creating, testing, and experimenting with digital circuits, making it a valuable tool for both learning and prototyping. With the flexibility and speed offered by the CPLD, you can dive into more complex designs, enhance your understanding of hardware programming, and take your DIY electronic projects to the next level.