The VTD comprises a SpO2 sensor with special features and a breath pressure sensor.  The idea behind this device is that when a patient is performing the "Valsalva Maneuver" (that is,  blowing hard with lips closed to build up pressure in mouth and lungs) there we be a rapid change in blood pressure that we can detect using the SpO2 sensor.  Normal SpO2 monitors are not sensitive to this, so a custom monitor was created.

We wound up winning 3rd place and also receiving special mention for "Best Medical Device".

Thanks to the prize money, we are able to continue developing this project.

We will update this page with progress in this project

This project was greatly helped by being able to use our (Rayslogic.com) products.  The project hardware is essentially the combination of these boards:

Propeller Platform Express:  Provides the Propeller microcontroller, USB programming interface, and power control.

4.3" breakout board and Samsung displays:  We are no longer selling these, but have a few left over.  Our available new Newhaven NH4 and NH4CT boards could just as easily be used.

The microMedic PCB was the custom board with SpO2 and pressure circuits needed for this project.  We may sell this board in the future for others looking into similar projects.  

Contest Submission Files

Here are all the files that we submitted as part of our entry to the contest:   

Project Report (pdf format)

Propeller source code (zip)

Photos (zip)

3D printed enclosure CAD and Makerbot files (zip)

Windows monitor program and source code (zip)

Recent Progress

Since the contest we are continuing development of the VTD, aided by the prize money.  Here are a couple areas that we are working on:

1. Recording measured data locally to SD or uSD

2. Wireless access to recorded data

3. Battery power

4. Improved LCD interface

5. Calibration of pressure and SpO2 circuits.

6. Fixing minor errors with circuit board 

 1&2:  Wireless SD cards (FlashAir)

The Toshiba FlashAir SD card provides us with a relatively low cost way to have wireless access to data stored on the SD card.  (Wish it was in uSD format though since the Propeller Platform Express board has one of those onboard.)

We originally tried EyeFi cards, but they didn't work with FSRW or any SD card code we could find for Propeller.

Unfortunately, adding the SD card code to our project put us over the 32kB memory limit.  We are going to have to rewrite the code from scratch to get around this...

3:  Battery power

Current thought is to add a Li-Ion-polymer battery.  We'll need a recharging circuit for this too.

We may make a new PCB for both the full size SD card slot and the battery circuit.

4:  Improved LCD interface

We probably need to reduce the size of the graphics area to accommodate SD card code and other improvements.  Perhaps we'll use the left side of the screen for graphics and the right side for controls.

We've already added a manual Zoom control to provide 1X, 2X and 4X zoom to account for some people having smaller SpO2 signals than others.  Perhaps this can be automated in the future.

We'd like to display some info such as SpO2 percentage and signal intensity as well.

5:  Calibration

We were able to calibrate the pressure circuit and found out that we were a factor of 2 off.  Found the error in the math and the new code has it right.

It would be nice to calibrate the SpO2 circuit, but we'll have to investigate how to do that.  We currently have a very basic algorithm for this based on the Freescale documentation. 

6:  Fixing circuit board errors

There were a couple of minor issues with the prototype circuit boards that required a few jumper wires to correct.  We are currently fixing this and preparing to order a new set of boards.

Also, the EKG circuit was tested and an error fixed there too.  The EKG circuit is not part of this project, but was included just because there was some extra board space and the circuitry is very similar to the other circuits on the board.  Also, there was a spare channel on the 4-channel DAC for the EKG data. 

Latest code version (3A)

Here is the latest version of the code that uses the graphics area as one big button to toggle vertical zoom between 1X,  2X and 4X.  We've also split the main code file in two with the data acquisition cog code turned into a sub-object file to improve code readability.  

microMedic board

This custom board provides SpO2, pressure and EKG circuits.  This board may soon be for sale.

The outputs of the three circuits goes to an onboard MCP3204 (4-channel ADC) chip that provides a simple, SPI, interface to the Propeller with the data.

The board itself is Propeller Platform compatible, and can easily be mounted to any Propeller Platform board.  Or, one can simply use 8 wires (2 for power, 4 for SPI interface, 2 for SpO2 control) to connect this board to any microcontroller setup.   The required connections are highlighted in yellow in the layout below: