Published December 6, 2018 © GPL3+

Smart Shoe Sensor

Insole for a shoe with sensors that measure weight applied on different areas of the foot and generates a colormap based on that data.

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Things used in this project

Hardware components

Texas Instruments LAUNCHXL-CC2640R2 SimpleLink CC2640R2F BLE LaunchPad

Texas Instruments CC2640

SaBLE-x-R2 Bluetooth Low Energy (BLE) Module

Raspberry Pi 3 Model B

SparkFun LilyPad LED Blue (5pcs)

AMD XUP USB-JTAG Programming Cable

3.7V Lithium Ion Battery

Micro-USB to USB Cable (Generic)

3 mm LED: Green

Texas Instruments BQ21040DBVT Charger IC

General Purpose Transistor PNP

Texas Instruments 3.0V Voltage Reference

8-to-1 Multiplexer

General-Purpose Op-Amp

Ferrite Bead

Capacitor 2.2 µF

Capacitor 10 µF

Capacitor 100 nF

Resistor 10k ohm

Resistor 1k ohm

Software apps and online services

Raspberry Pi Raspbian

Texas Instruments Code Composer Studio

Texas Instruments Sensor Controller Studio

Texas Instruments TI-RTOS

Altium Designer

Thonny

Hand tools and fabrication machines

Soldering iron (generic)

Infrared IC Heater

Story

The Shoe Crew is a senior design team from Purdue University's ECE 49022 course. Our project was conceived as a way to help athletes who are returning from injury monitor their progress during physical therapy by giving them quick and easy-to-understand information about their stride.

The Smart Shoe Sensor uses a homemade shoe insert equipped with sensors connected to a small PCB outside the shoe that can be strapped to the user's ankle. The PCB is equipped with a CC2640R2 microcontroller module that can connect to an external device via BLE to transmit data from the sensors. We used a Raspberry Pi to receive the data and run a script to plot a color map showing the weight applied to each sensor

The shoe insert is made of conductive foam and has 8 sensors attached to it. Each sensor consists of a small, rectangular copper plate on top of the foam with a shared ground plate on the bottom of the foam. Using a multiplexer, each sensor is delivered a reference current of 600 nA one at a time. The voltage across the currently-active sensor is then read by the CC2640R2 using its ADC. When the conductive foam is depressed, its resistance decreases, allowing us use the resultant voltage across the sensor to determine the magnitude of the weight being applied.

The CC2640R2's programming is based off the Simple BLE5 Peripheral example code from TI's SimpleLink SDK version 1_35_00_33. Once it reads a single value it changes the multiplexer select value to activate and read the next sensor. The BLE GATT profile of the peripheral consists of only 1 characteristic, the value of which is an array containing the most recent values of all 8 resistors. This characteristic is read by the connected Raspberry Pi and used to create a color map.

A sample of our color map. Red means more weight, blue means less weight, and yellow is in between

Our PCB is battery-powered to ensure that the user can move freely without being tied down by a power cable. The 3.7V Lithium Ion battery is used to deliver 3.3V power source to the CC2640R2 and other various ICs used on the PCB. The battery is rechargeable thanks to an embedded TI Charger IC and a microUSB port that allows it to be charged with a generic microUSB to USB cord.

Check out this video demo of the Smart Shoe Sensor in action!

Code

import matplotlib
import numpy as np
import matplotlib.pyplot as plt
import matplotlib as mpl
import matplotlib.image as mpimg
import matplotlib.cm
import pprint
import matplotlib.animation as anim
import time
import pylab
from matplotlib import colors as mcolors
from matplotlib import cm
from bluepy import btle
from matplotlib.pyplot import *

cmap = matplotlib.cm.get_cmap("jet")

print ("Connecting..")
dev = btle.Peripheral("A4:34:F1:7D:7A:E1") #PCB = A4:34:F1:7D:7A:E1, Launchpad = 54:6C:0E:A0:4D:48

print ("Services..")
svc = dev.getServiceByUUID(0xfff0);
print (str(svc))
test_data = [20, 20, 500, 2500, 1400, 1200, 2830, 34]
plot_colors = ['bo', 'bo', 'bo', 'bo', 'bo', 'bo', 'bo', 'bo']
result = [0, 0, 0, 0, 0, 0, 0, 0]

img = mpimg.imread('foot3.png')

plt.ion()
fig, ax = plt.subplots()

im = ax.imshow(img)

def demo():
    cl = svc.getCharacteristics(0xfff1);
    for c in cl:
        print (str(c))
        data = c.read()
    print (data)

    for b in [0,2,4,6,8,10,12,14]:
        lsB = int(data[b])
        msB = int(data[b+1])
        r = int(b/2)
        result[r] = 256*msB + lsB
        print(result[r])
    for q in range(8):
        t_data = result[q]
        if t_data < 1000:
            plot_colors[q] = 'ro'
        elif t_data < 2000:
            plot_colors[q] = 'yo'
        else:
            plot_colors[q] = 'bo'
    
    plt.plot(127,230, plot_colors[7], markersize=28);
    plt.plot(127,200, plot_colors[6], markersize=28);
    plt.plot(127,170, plot_colors[5], markersize=28);
    plt.plot(145,105, plot_colors[2], markersize=28);
    plt.plot(145,140, plot_colors[4], markersize=28);
    plt.plot(115,140, plot_colors[3], markersize=28);
    plt.plot(115,105, plot_colors[1], markersize=28);
    plt.plot(110,72, plot_colors[0], markersize=28);


while 1:
    demo()
    plt.pause(0.1)
    plt.draw()


dev.disconnect()

Credits

The Shoe Crew

1 project • 0 followers

A team of 4 senior ECE students from Purdue University Eashvar Venkatraman Remy Hoang Daniel Gilmore James Gradowski

Smart Shoe Sensor

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Schematics

PCB Layout

Microcontroller Schematic Document

Power Supply Schematic Document

Sensor schematic document

PCB Library

Microcontroller Schematic Image

Power Supply Schematic Image

Sensor Schematic Image

Code

BLE Peripheral

FinalProject.py

Credits

The Shoe Crew

Comments

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Smart Shoe Sensor

Smart Shoe Sensor

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Schematics

PCB Layout

Microcontroller Schematic Document

Power Supply Schematic Document

Sensor schematic document

PCB Library

Microcontroller Schematic Image

Power Supply Schematic Image

Sensor Schematic Image

Code

BLE Peripheral

FinalProject.py

Credits

The Shoe Crew

Comments

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