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Raspberry Pi HAT connects up to three Pmod modules at once

Jan 20, 2018 — by Eric Brown 2,001 views

Digilent and RS Components have launched a $15, Python supported “Pmod HAT Adapter” for the Raspberry Pi that can connect up to three Digilent Pmod peripheral modules at a time while also extending the 40-pin adapter.

Digilent has joined with distributor RS Components to co-launch a $15 DesignSpark Raspberry Pi Pmod HAT Adapter board that brings Digilent’s Pmod peripheral boards to the Raspberry Pi. The 65 x 56.5mm HAT compliant board offers three 2×6-pin Pmod ports with support for I2C, SPI, UART and GPIO interfaces. The Raspberry Pi’s 40-pin adapter is extended to make full use of the SBC’s interfaces.

Pmod HAT Adapter, front and back
(click images to enlarge)

Digilent’s Pmod (Peripheral Module) adapters are commonly found on MCU- and FPGA boards, including Linux-driven hybrid FPGA boards like Avnet’s Xilinx Zynq based MiniZed and MicroZed. Designed for rapid prototyping, the compact Pmod modules are available in 6- and 12-pin versions.

The Pmod HAT Adapter currently supports six Pmod modules, three of which can be connected at once. Two jumpers are also available, as well as an EEPROM that stores a device tree fragment for identifying the module and configuring the OS and drivers.


The HAT can draw power from the Raspberry Pi or via a 5V barrel jack, and supplies “3V3” Pmod and HAT logic levels. The board can work with the RPi Model A+, Model B+, Pi 2 B, Pi 3 B, and the Zero and Zero W.

Pmod HAT Adapter (left) and PmodISNS20 Hall Effect current sensor
(click images to enlarge)

Supported modules include the PmodMIC3 ADC module, the PmodTC1 SPI module, and the dual-channel, 12-bit ADC PmodAD1. Other modules include the PmodISNS20 Hall Effect current sensor and PmodHB3 2A H-bridge circuit for DC motor drives up to 12V. There’s also a PmodOLEDrgb organic RGB LED module with a 96x64pixel display and 16-bit color resolution.

PmodOLEDrgb hooked up to the Pmod HAT Adapter
(click image to enlarge)

The Pmod HAT Adapter includes a Python-based, MIT-licensed DesignSpark.Pmod library specifically designed to bring Raspberry Pi Python developers up to speed with the Pmod world. The library includes “simple, consistent interfaces for supported Pmods,” and provides startup examples, says RS Components. It also taps the EEPROM device tree to check that Pmod and port capabilities match and that ports do not conflict.

This is not the first RPi add-on to include Pmod connectors: Pi 2 Design includes two Pmod interfaces on its 502IoT Shield, and Black Mesa Labs sells an IceZero add-on that supplies several Pmod interfaces driven by an onboard Lattice ICE40HX4K FPGA. The much more affordable Pmod HAT Adapter is, however, the first Pmod enabled HAT board and the first RPi add-on devoted solely to Pmod prototyping. The fact that it originates from the company that developed the open Pmod standard implies a guarantee of compatibility.

Further information

The DesignSpark Raspberry Pi Pmod HAT Adapter is available for $15 at Digilent and 14 Pounds at RS-Components. More information may be found in the announcement on RS-Components’ RS-Online DesignSpark site, as well as at Digilent’s Pmod HAT Adapter product page.

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