Datasheet

Digilent Pmod™ Interface Specification 1.2.0

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Peripheral modules may be connected to the host via cables of up to 18” in length. The drivers on the host or

peripheral module should have sufficient drive strength to drive this length of cable at whatever the operating

speed of the interface on the Pmod is expected to be. In general, this means that the driver should be able to

source or sink at least 5 mA of current.

With the exception of I

C connected modules, peripheral modules may not assume that pull-up or pull-down

resistors are present on the host and must provide for proper termination of inputs, if necessary, and may not use

open drain or open collector outputs, unless the pull-up is provided on the peripheral module itself.

For all I

C connected modules, the digital signal characteristics conform to the I

C specification. Either 5 V or 3.3 V

levels can be used on most modules, but Digilent system boards operate at 3.3 V, and the modules are primarily

intended for operation at 3.3 V.

Prior to the Digilent Pmod Interface Specification 1.1.0, I2C modules were not required to have onboard pull-ups.

Therefore, it is suggested to include jumpered pull-ups on system boards to be backward compatible with old I2C

Pmods. However, all Pmods designed to conform to specification version 1.1.0 and higher will include onboard

pull-ups that can be jumpered in and out.

3 Power Supply

The power pins of the interface provide power from the host to the peripheral. The interface requires that the host

provide 3.3 V at the power supply pins. Digilent system boards use exclusively 3.3 V at the power supply pins;

however, the host is allowed to provide the ability to switch the voltage on the power pins between 5.0 V and 3.3

V. On the twelve-pin version of the interface, both power supply pins switch together and always supply the same

voltage, if switching is provided as an option. These pins may be shorted together at either the host end or the

peripheral end.

On I2C connected modules, the power pin of the interface provides power from the system board to the

peripheral module. The supplied voltage will generally be 3.3 V, but operation at 5 V is supported by some

modules. Care should be taken to ensure 5 V will not damage the host’s input pins. Daisy chaining six-pin I2C

connected modules is possible via the female connector on the board edge opposite the male connector.

The amount of power a peripheral module is allowed to draw from the host is not specified, but should not be

assumed to be more than approximately 100 mA.”

4 Physical Connection Standard

Pmod connections are made using standard 100 mil spaced, 25 mil square, pin-header style connectors.

The peripheral module board will have a male connector. This will typically be a right-angle connector, at the board

edge, for direct connection to a host board. Some older I²C modules have a straight male connector inboard from

the board edge as only cable connections were intended to be used. Beginning with Pmod Specification 1.1.0, all

connectors intended for primary connection to a host board should be right angle male connectors.

Six-pin I²C modules will have a six-pin female connector, centered on the board edge opposite the male connector.

This will typically be a right-angle connector at the board edge and is intended to be used in daisy chaining.