Evaluation boards
There is no shortage of FPGA evaluation boards available for us to purchase. One company that makes very affordable boards is Digilent. There are several nice features that their boards tend to include, but one of the best is that they have a USB to UART controller built in that Xilinx Vivado recognizes as a programming cable. This makes configuring the device painless. The recommended boards also have the added advantage of being powered over this same USB cable.
Nexys A7 100T (or 50T)
The Nexys A7 is the recommended board for this book. It has all the devices we'll target over the course of the book:
Figure 1.11 – Digilent Nexys A7 board
The board features are as follows:
- Artix-7 XC7A100T or 50T
- 450+MHz operation
- 128 MB DDR2
- Serial Flash
- Built-in USB UART for downloading images and ChipScope debugging
- MicroSD card reader
- 10/100 Ethernet PHY
- PWM audio output/microphone input
- Temperature sensor
- 3 axis accelerometer
- 16 switches
- 16 LEDs
- 5 pushbuttons
- Two 3 color LED
- Two 4-digit 7-segment displays
- USB host device support
- Five PMOD (one XADC)
Let's take a look at the breakdown of the two devices the Nexys board can be ordered with:
One benefit to choosing the XC7A100T is the additional RAM. Especially when starting out you may find yourself relying on chip debugging using ChipScope and the additional RAM will allow for additional storage for wider busses or longer capture times. We'll discuss ChipScope in a later chapter.
Basys 3
An alternative evaluation board is the Basys 3:
Figure 1.12 – Digilent Basys 3 board
This board has the same pushbuttons, LEDs, and switches, but only half the number of seven segment displays. We'll be developing code that can run on either board using these features. It does lack the DDR2 RAM, so it will limit using this for a framebuffer as we will introduce in a later chapter. It is also missing the temperature sensor, microphone, and audio, which we'll look at regarding serial interfaces. PMOD boards can be purchased that have this functionality, however, to overcome this limitation.
The board features are as follows:
- Artix-7 XC7A35T
- 450+Mhz operation
- 128MB DDR2
- Serial Flash
- Built-in USB UART for downloading images and ChipScope debugging
- MicroSD card reader
- 10/100 Ethernet PHY
- PWM audio output/microphone input
- 16 switches
- 16 LEDs
- 5 pushbuttons
- Two 3-color LEDs
- Single 4-digit, 7-segment displays
- USB host device support
- Four PMODs (one dual purpose supporting XADC)
Let's now take a look at the breakdown of the Basys 3 board:
Important note
The Basys 3 board lacks the DDR 2 memory, accelerometers, and audio capabilities, which will be addressed in later chapters. PMODs are available for everything apart from the DDR2. I would recommend the Nexys A7 over the Basys if possible.
We've just taken a look at the boards we are planning on using for the book. Now we need to take a look at the Xilinx tool, Vivado, which will be what we use to design, simulate, implement, and debug our FPGA designs.
