KNJN Pluto - TXDI connector; Secondary connector

9.6 TXDI connector
It is usually used to power the Pluto board and for RS-232 communication.
1. GND
2. TxD (FPGA → PC)
3. RxD (PC → FPGA)
4. VCC-unreg (board power, typically +5V to +10V)
See chapter 15 for more information.
9.7 Secondary connector
The secondary connector is placed on the left side of the board. If it is not present, it can be easily soldered (available as
KNJN item#180 4 or from DigiKey).
The secondary connector has only 4 pins (2 power pins and 2 IOs), and so is usually limited to applications requiring a
serial bus. Possible applications include:
● Graphic LCD
● I²C interface
The pin assignments are:
Pin Pluto Pluto-II Pluto-IIx Pluto-IIx HDMI Pluto-3 Comment
1 VCC-unreg VCC-unreg 3.3V 3.3V VCC-unreg Power
2 FPGA IO pin 8 FPGA IO pin 26 FPGA IO pin 43 FPGA IO pin 57 FPGA IO pin 30 RxD or serclk or other use
3 FPGA IO pin 96 FPGA IO pin 27 FPGA IO pin 44 FPGA IO pin 59 FPGA IO pin 31 TxD or serdata or other use
4 GND GND GND GND GND Ground
In more details:
● VCC-unreg is the voltage that you power your FPGA board with, typically +5V to +10V.
On Pluto and Pluto-II, VCC-unreg can be disconnected from the secondary connector by cutting the trace placed
between the two pads close to the VCC-unreg pin.
● Pins 2 & 3 are two FPGA IO pins. The board includes series termination resistors, and Zener protection diodes on
these 2 signals (Pluto/-II/-3 only).
● Some revisions of Pluto-II have another secondary connector on the right side of the board, below the power
header.
FPGA RS-232 development boards Page 14