Biomedical User Group Discussions
ECG/EMG wireless transmission using arduino,xbee & VISA
Hello to all biomedical user group members. 
Im currently working on a university course project in which my goal is to transmit EMG waveform (measured using a circuit i constructed) wirelessly to a computer and write a Labview VI to observe both the EMG signal and EMG spectrum in real time. Even though this project is on EMG, i think similar methods are used when transmitting other biosignals such as ECG. I have taken the following steps:
1) Output (and ground) from the EMG circuit is connected to an analog input pin (and ground) of an arduino. I have yet to construct the EMG circuit, therefore for now I am using a function generator to supply sine waves as a substitute for the EMG circuit
2) I have used the following code for the arduino. Arduino input pins have inbuilt ADC. The digitized values range from 0 to 600, representing 0 to 3 volts. This program consists of two loops, the first ensures 800 points/values of the waveform are read into an array. The second loop is used to send these 800 points to the serial/COM port.
#define POINTS 800
int value[POINTS]; // variable to store the value coming from the sensor
int i=0;
void setup()
{
Serial.begin(9600) ;
}
void loop()
{
for (i=0;i<POINTS;i++)
{
value=analogRead(0);
}
for (i=0;i<POINTS;i++)
{
Serial.println(value);
}
delay(0.5);
}
3) I have attached the labview VI (serial_arduino3.vi) used to read serial data from the serial/COM port. I do manage to get a smooth sine wave but there is a periodic discontinuty due to the program on the arduino side - after reading 800 samples into an array, there is a delay before the 800 samples are sent to the serial/com port. I have attached images of the sine waves with discontinuity (discontinuity_sine1.JPG) and (discontinuity_sine2.JPG).
4) The RS-232 to USB cable can be substituted with a pair of xbee radios for wireless data transmission.
5) Sine waves at various frequencies 20Hz,30Hz...up to 300Hz can be transmitted well and smooth sine waves appear on the labview waveform chart (except for the periodic discontinuity part).
I would like to ask:
a) Since I have managed to transmit sine waves at various frequencies, 20Hz,30Hz...up to 300Hz. Can I replace the function generator with an EMG amplifier circuit (with filtering) and expect to see nice EMG signals on the Labview waveform chart?
b) Since the sine wave I got has discontinuities, when i try to find the fourier transform of the sine wave there is 'spectral leakage'. The amount of spectral leakage depends on the amplitude of the discontinuity. I have read about windowing techniques such as Hamming window which can be used to solve the spectral leakage problem. Can these windowing techniques be used for EMG signals also? Im interested to see the EMG spectrum also.
I appreciate any feedback and suggestion from all of you.
Thanks!
