Sip and Puff (SNP) devices are one example of Assistive Technology that allow one to interact with things by applying negative or positive pressure to a straw or tube in their mouth. This is done by either sipping on the tube, like a straw, or puffing into it, like when you blow bubbles in your milk until your parental unit (or partner) makes you stop.

Sip and Puff devices have been around for a while. They have helped many people who aren't able to use things like keyboards, mice or other input devices that were designed to be used with hands. There are a number of commercial options, however a newer trend is towards people and groups developing open source designs. These can be made with off the shelf and 3D printed parts by gathering the materials, assembling them, and programming them with open source software.

There are many open source sip and puff devices around A well-known example is LipSync which was developed by Makers Making Change, and released by the Neil Squire Society with support from Google.org. Lots of technical detail can be found on the project's GitHub page. The LipSync also integrates a joystick and mount for attaching to wheelchairs, and works as an input device to allow people operate a touchscreen device.

Here, we show how with the right sensors, microcontrollers, and software, it can be relatively easy to make a very basic but expandable Sip and Puff device. It is a fun, easy project that you can use to learn a bit more about them and how they might be used.

The heart of this project is a STMicroelectronics (ST) LPS33HW MEMS pressure sensor mounted to an Adafruit breakout board with built in STEMMA QT connectors and support circuitry. Importantly the LPS33HW has a metal port on top like a hat and a groove for fitting an o-ring. With 24-bit pressure data output, an absolute pressure range of 260-1260 hPa ( hectopascals ), and the ability to work in absolute or relative modes, this sensor is the perfect tool for the job.

The brains of the operation is a ST STM32F405 based express Feather running CircuitPython. The STM32F405 is a fast chip with plenty of memory so it's great for CircuitPython use, and the STEMMA QT connector on the end makes this a plug-n-play project

Many thanks are due to Bill Binko of ATMakers.org for his work making Assistive Technology more widely accessible, and for taking the time to educate me on Sip and Puffs and Assistive Technology in general. Bill has his own CircuitPython powered Sip and Puff, the AirTalker, developed with his friend Jim to meet his needs. It even includes Morse Code detection!

Parts and Materials

To follow along and make your own ST LPS33HW powered Sip and Puff, you'll need the items below. Additionally if you are inspired to take it further, check out the bits on the Extending the Capabilities page for more ideas.

Pick a Cable

The Feather STM32F405 Express requires a USB C cable which you may not have. Pick the one below that fits your computer. Most PCs will have USB Type A. Macs made in the last few years will likely have a USB C port which is also referred to as Thunderbolt.

If you're not sure, take a look at the pictures for each cable and compare them to the ports on your computer before ordering

Optional Tool: Flush Cutters

Optional Fasteners:

The guide shows using these nylon screws, nuts, and standoffs to hold the boards together. Pick these up if you want to take that approach, or find a different M2.5 fastener if you wish to take a different approach.

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