The Butterfly One is a Gadget development board based on the Xilinx Spartan 3E FPGA (datasheet). It has 48 I/O lines, dual channel USB, integrated JTAG programmer, 4 power supplies, and a power connector. It provides everything needed to make Gadgets using Arduino compatible sketches or standard VHDL/Verilog. Hardware can be added without any soldering or bread boarding using the provided "Wing" slots. The Butterfly One places the focus on bringing Gadgets to life rather than reading through datasheets.

The Butterfly One can be purchased in the online store:
Butterfly One with 250K Xilinx Spartan 3E
Butterfly One with 500K Xilinx Spartan 3E

 

• Power
  • Four independent power rails at 5V, 3.3V, 2.5V, and 1.2V.
  • Power supplied by a power connector or USB.
  • DC Input Jack
    • Input Voltage (recommended): 6.5-15V
• USB
  
  • Two channel USB connection for JTAG and serial communications implemented with FT2232D.
  • EEPROM memory to store configuration settings for FT2232 USB chip.
• Spartan 3E FPGA
  • 32MHz oscillator that can be used by Xilinx's DCM to generate any required clock speed.
  • VTQFP-100 footprint that supports Xilinx XC3S100E, XC3S250E, and XC3S500E parts.
  • I/O can be jumpered to support 1.2V, 2.5V, or 3.3V.
• SPI Flash
  • Atmel AT45DB021D 2M SPI Flash
• Wings
  • 48 bidirectional I/O lines which can be split up as:
    • 1 - 32 Bit Wing or
    • 3 - 16 Bit Wings or
    • 6 - 8 Bit Wings
  • .1" spacing for compatibility with bread boards.

• Documentation - Quickstart Guides, User Guide, Pinouts
  • Project Wiki
• User Constraint Files (UCF) - Defines all pins and clock for Papilio One board.
  • File Repository
• Eagle PCB schematic and board files.
  • SVN repository
• Arduino/Wiring development environment to make Gadgets using Arduino compatible sketches.
  • Papilio Wiring/Arduino IDE
• Papilio/Butterfly Loader to make Gadgets using VHDL/Verilog with the free Xilinx Webpack IDE.
  • Papilio/Butterfly Loader
• Sump Logic Analyzer to use the Butterfly One as a logic analyzer.
  • Sump Logic Analyzer
• Complete list of Wings to add peripheral functionality without soldering or breadboarding.
  • All Wings

The Butterfly One can be powered from the USB connector, an external power supply, or a battery. The PWRSELECT jumper controls whether the USB connector or the Power Jack/PWRIN connectors are active.

Power Selection

When the USB connector is selected up to 500mA of current is supplied to the 1.2V, 2.5V, and 3.3V LD1117 voltage regulators. The 5V power rail is supplied directly by the USB port and the 5V LD1117 power regulator is inactive.

When the power jack or battery is selected the 5V LD1117 voltage regulator supplies up to 800mA of current to the 1.2V, 2.5V, and 3.3V LD1117 voltage regulators. The power jack or battery must provide at least 6V in order to generate the desired 5V output.

I/O Bank Power Selection

The VCCO jumper selects the voltage for all of the I/O lines, the options are 1.2V, 2.5V, and 3.3V. The recommended setting is 3.3V since most peripherals operate at 3.3V.

RPAR

The JTAG programming pins on the Spartan 3E always operate at 2.5V while the connected JTAG pins of the FT2232D always operate at 3.3V. This difference in voltage can cause the Spartan 3E to send reverse current back on the 2.5V power rail. The RPAR resistor provides a shunt for this reverse current to be dissipated. The Xilinx application notes recommend the use of RPAR in the case that a voltage regulator cannot handle reverse current. The LD1117 datasheet does not indicate that it can handle reverse current so RPAR was included. Testing has shown that the LD1117 seems to handle the reverse current just fine but boards will be populated with RPAR as a safety precaution. The RPAR resistor consumes 25mA of current so if a battery is being used it is recommended to remove the RPAR resistor to help extend battery life. Please understand that the possible effects of removing the RPAR resistor are the 2.5V rail going higher than 2.5V and possibily damaging the 2.5V voltage regulator.

Power Jack

• Input: 6-15V DC
• Current: Draws up to 800mA
• Size: 2.1mm
• Polarity: Positive Tip

 

The onboard Atmel AT45DB021D SPI Flash provides 2Mbits of space to store a bitstream that is loaded by the FPGA at startup.

The Butterfly One uses a FTDI 2232D USB chip which provides two channels over one USB connection. One of the channels is configured as a simple UART device and shows up as a virtual COM port. The other channel takes advantage of the MPSSE (Multi-Protocol Synchronous Serial Engine) functionality to implement a high speed JTAG channel for programming the Xilinx Spartan 3E.

Drivers
The first time the Butterfly One is plugged into the computer it will be necessary to install the FTDI device drivers. Drivers can be downloaded from the FTDI website.

UART
When the Butterfly One is plugged into the USB port both channels will be detected and will show up under the Control Panel as a virtual COM port. The second virtual COM port is the UART channel.

JTAG
The Xilinx device is programmed using any application that can support the FT2232D MPSSE JTAG mode. The Butterfly Loader is one such application.

JTAG Programming Port
The JTAG programming port is included for use with external JTAG programmers such as the Xilinx JTAG cables. The Xilinx tools such as Impact and the EDK do not support FT2232D based programmers nor does Xilinx provide any method to add support for non-Xilinx programmers. This external port is provided as a means to use the Xilinx tools with the Butterfly One. The Xilinx tools can still be used without an Xilinx programmer by generating bitstreams that can be loaded by the Butterfly Loader.
TEMPORARY LIMITATION: In order to use the external JTAG port the FT2232D lines that are connected to the JTAG port need to be put into a HIGH-Z state. This has not been tested yet and will probably require a special application.

EEPROM
Custom VID/PID and configuration data can be loaded into the provided EEPROM using the FTDI MProg application.

Oscillator

The Butterfly One has a 32Mhz oscillator that can be converted to any speed desired inside the FPGA using a Digital Clock Manager. The Spartan 3E provides 4 Digital Clock Managers.

LED's

The Butterfly One has a power LED, a RX LED, and a TX LED. The power led lights up to indicate that power is being supplied to the board while the RX and TX led's show UART traffic.