Introduction: LinkIt One Remote Heart Rate Monitor

This instructable demonstrates how to build a Wifi enabled Heart Rate Monitor using Mediatek LinkIt One development kit. The heart rate is determined using photoplethysmograph (PPG) signal obtained from the subject's finger tip. The heart rate information is periodically uploaded to a cloud application developed in Mediatek Cloud Sandbox where it can be viewed anytime.

The project involves building an add-on board for the Linkit One development board. The add-on board has the required analog front end to acquire the PPG signal and a low power microcontroller to extract Heart rate information.

The add-on board is designed with arduino compatiable pinout so that it can be easily mounted on the Linkit One board. On the other hand the Linkit One will run an application which collects the heart rate information periodically and uploads it to a cloud application using its Wifi connectivity. The heart Rate information can then be view in the cloud application whenever needed.

Step 1: Building Heart Rate Add-on Board

This step describes how to build the Heart Rate addon board.

Item Required:

  1. General Purpose PCB: 1No
  2. 100 mil Extra long male header(berg sticks) 8x1: 2No
  3. 100 mil Extra long male header(berg sticks) 6x1: 1No
  4. TLC2274 Quad OPAMP: 1No
  5. MSP430G2553: 1No
  6. Resistors: 10K, 4.7M, 82K, 120R
  7. Capacitors: 0.22u
  8. 10 Pin and 14 Pin IC base
  9. SpO2 Sensor
  10. DB9 Female Connector
  11. MSP430 Launchpad (to program the MSP430 controller)

Any QUAD OPAMP that can operate at 3V can be used. In case the SpO2 Sensor is not available a DIY sensor can be designed as shown.

Construct the circuit as show in the schematic shown below.

Burn the attached HEX file on the Controller via the debug port using a MSP430 Launchpad and IAR workbench.

Note: The reason why an additional processor (MSP430G2553) is used to calculate Heart rate rather than doing the processing on the LinkIt one itself is because LinkIt One "analog.Read()" function requires 20ms for every conversion which is too slow for heart rate calculation. See here for more details

Step 2: DIY PPG Sensor

In case SpO2 sensor is not available then a sensor can be constructed using a IR led and Photodiode. The construction is shown.

Step 3: Creating MCS Cloud Application

Create an account in Mediatek Sand Cloud box and follow the images to create a Cloud application.

Make note of Device ID and Device Key that are to be added in the arduino sketch.

Step 4: Arduino Sketch

Upload the firmware on to LinkIt One board using the sketch provided.

Note: Change the following appropriately

  1. WIFI_AP

Step 5: Testing!!!

Connect the Wifi Antenna and battery to LinkIt One board and also mount the Addon Board on LinkIt One. Connect SpO2 probe and put it onto a finger and switch on power.

The heart rate data can be seen on the cloud application which updates periodically.