This is a simple EMG Controller for a bionic hand prosthesis

Dependencies:   mbed-dsp mbed NOKIA_5110

Galileo Bionic Hand - ST Nucleo Example


This is an example of a simple hybrid sEMG(surface Electromyography) activated controller for the Galileo Bionic Hand Prosthesis implemented with the Galileo EMG Shield. The user has to select the desired posture by sending a special character through serial port (115200 baud rate) and then perform it through sEMG activation by detecting contraction on flexor muscles of the forearm. Contractions on forearm extensor muscles releases the posture and allows the return to the default or rest posture.

Special characters:

  • '1', for "Power Grip" selection
  • '2', for "Point" selection
  • '3', for "Pinch Grip" selection
  • '4', for "Lateral Grip" selection
  • '5' for "Tripod Grip" selection


Galileo EMG Shield - 3 Channels for surface EMG

The electrodes for sEMG are placed on the skin surface and are connected to the input of a precision instrumentation differential amplifier based on Texas Instruments (TI) INA122, then its output is passed through an active low pass filter (LPF) based on TI OPA335 in order to sense the action bio-potentials of the muscular fibers with an output signal span in the range of 0 to 3.3V and a bandwidth between 0 to 500 Hz. The circuit is built-in on a custom PCB with 3 sEMG channels and a bias voltage reference output (1.25 V); furthermore, it is pin compatible with Arduino pin compatible ARM Cortex M4 boards and mbed platform ecosystem (ST Nucleo F411RE, Freescale FRDM K64F, NXP LPCXpresso 4337, ST Discovery F746NG, Renesas GR-Peach, etc), which is ideal for the single ended input of a microcontroller in addition to contributing to low cost development kits. /media/uploads/julioefajardo/shieldbrd.png /media/uploads/julioefajardo/image1.jpg

Electrodes Placement and Connection

Standard surface mounted Ag/AgCl electrodes with wet conductive gels are placed on palmaris longus and extensor digitorum muscles (third channel could be placed on Flexor carpi Ulnaris), focusing only on below elbow disarticulation. These electrodes have been well-characterized and most of its properties are well understood, except for some properties as drifting and low-frequency noise. Nevertheless, with proper preparation of the skin, the sEMG signal is excellent.

Disposable electrodes and snap leads information:

Proper placement of disposable electrodes for two channels of surface EMG is shown below:

/media/uploads/julioefajardo/electrodes.png /media/uploads/julioefajardo/mucles.png

Customizable Postures

You can customize the actions by modifying PWM values (microseconds) on FingerPosition function (values depends on the way that the hand was built it). The prosthesis has five fingers and a thumb rotation mechanism and five actuators in order to perform multiple types of grasping. Wrist rotation will be implement later.

The servo motors have to be connected as shown below:


Function Declaration and Usage Examples

include the mbed library with this snippet

void FingerPosition(float32_t thumb_us, float32_t index_us, float32_t middle_us, float32_t pinky_us, float32_t thumbrot_us);

FingerPosition(2400, 600, 600,2400,2400);   //Close
FingerPosition(2400,2400, 600,2400,2400);   //Point
FingerPosition(2400, 600,2400, 600,2400);   //Pinch
FingerPosition(2400, 600, 600,2400, 600);   //Lateral
FingerPosition(2400, 600, 600, 600,2400);   //Tripod
FingerPosition(1000,2400,2400, 600, 600);   //Open

Serial Oscilloscope Feature

This feature easily allows to watch and log to file the data using serial oscilloscope software (115200 baud rate).

  • Serial_Osciloscope(TRUE,RAW) to watch raw signals, FALSE deactivate this feature
  • Serial_Osciloscope(TRUE,RECTIFIED) to watch rectified signals, FALSE deactivate this feature
  • Serial_Osciloscope(TRUE,SMOOTH) to watch smooth signals, FALSE deactivate this feature


Universal Real-Time Software Oscilloscope GUI information:

Nolia 5110 LCD

Nokia 5110 display implementation for visual feedback will be add later, we have to modify libraries and fonts in order to improve the functionality. The main idea is to change of action by pressing a push button and change thresholds using a potentiometer.



Videos, bill of materials and tutorials to build the Galileo EMG Shield and the Galileo Bionic Hand will be posted soon, more information on:

Sun Nov 01 18:35:45 2015 +0000
FRDM EMG Galileo Hand Basic Examples

Who changed what in which revision?

UserRevisionLine numberNew contents of line
julioefajardo 0:f2b89c6a8a16 1 #include "mbed.h"
julioefajardo 0:f2b89c6a8a16 2 #include "arm_math.h"
julioefajardo 0:f2b89c6a8a16 3
julioefajardo 5:49c5553b6e2c 4 #define TRUE 1
julioefajardo 5:49c5553b6e2c 5 #define FALSE 0
julioefajardo 5:49c5553b6e2c 6 #define RAW 0
julioefajardo 5:49c5553b6e2c 7 #define RECTIFIED 1
julioefajardo 5:49c5553b6e2c 8 #define SMOOTH 2
julioefajardo 5:49c5553b6e2c 9 #define THRESHOLDF 0.25f
julioefajardo 5:49c5553b6e2c 10 #define THRESHOLDE 0.25f
julioefajardo 5:49c5553b6e2c 11 #define FLEXION2 0.0f
julioefajardo 4:d8fd3c4484cc 12
julioefajardo 0:f2b89c6a8a16 13 Ticker EMG_Sampler;
julioefajardo 6:78494092a326 14 //Serial pc(SERIAL_TX, SERIAL_RX);
julioefajardo 6:78494092a326 15 Serial pc(USBTX, USBRX);
julioefajardo 0:f2b89c6a8a16 16 DigitalOut myled(LED1);
julioefajardo 6:78494092a326 17 InterruptIn sw2(SW2);
julioefajardo 0:f2b89c6a8a16 18 AnalogIn Ref(A0);
julioefajardo 0:f2b89c6a8a16 19 AnalogIn E1(A1);
julioefajardo 0:f2b89c6a8a16 20 AnalogIn E2(A2);
julioefajardo 0:f2b89c6a8a16 21 AnalogIn E3(A3);
julioefajardo 3:f784301a5166 22 PwmOut Thumb(D11);
julioefajardo 3:f784301a5166 23 PwmOut Index(D10);
julioefajardo 3:f784301a5166 24 PwmOut Middle(D9);
julioefajardo 3:f784301a5166 25 PwmOut Pinky(D6);
julioefajardo 3:f784301a5166 26 PwmOut ThumbRot(D5);
julioefajardo 0:f2b89c6a8a16 27
julioefajardo 5:49c5553b6e2c 28 //EMG samples and DSP variables
julioefajardo 0:f2b89c6a8a16 29 float32_t EMG1, EMG2, EMG3;
julioefajardo 2:12f979d695db 30 float32_t samples[25];
julioefajardo 2:12f979d695db 31 float32_t samples2[25];
julioefajardo 2:12f979d695db 32 float32_t samples3[25];
julioefajardo 2:12f979d695db 33 float32_t abs_output[25];
julioefajardo 2:12f979d695db 34 float32_t abs_output2[25];
julioefajardo 2:12f979d695db 35 float32_t abs_output3[25];
julioefajardo 5:49c5553b6e2c 36 float32_t mean = 0.0f;
julioefajardo 5:49c5553b6e2c 37 float32_t mean2 = 0.0f;
julioefajardo 5:49c5553b6e2c 38 float32_t mean3 = 0.0f;
julioefajardo 5:49c5553b6e2c 39
julioefajardo 5:49c5553b6e2c 40 //variables for state machines
julioefajardo 4:d8fd3c4484cc 41 uint8_t state = 0;
julioefajardo 6:78494092a326 42 uint8_t action = '0';
julioefajardo 5:49c5553b6e2c 43
julioefajardo 5:49c5553b6e2c 44 //conversion and data collection complete flag
julioefajardo 0:f2b89c6a8a16 45 uint8_t COCO = 0;
julioefajardo 0:f2b89c6a8a16 46
julioefajardo 5:49c5553b6e2c 47 //functions declaration
julioefajardo 5:49c5553b6e2c 48 void PWM_Init(void);
julioefajardo 4:d8fd3c4484cc 49 void ADC_Sampler(void);
julioefajardo 5:49c5553b6e2c 50 void RX_Interrupt(void);
julioefajardo 5:49c5553b6e2c 51 void Serial_Oscilloscope(uint8_t activation, uint8_t type);
julioefajardo 5:49c5553b6e2c 52 void FingerPosition(float32_t thumb_us, float32_t index_us, float32_t middle_us, float32_t pinky_us, float32_t thumbrot_us);
julioefajardo 6:78494092a326 53
julioefajardo 6:78494092a326 54 void flip() {
julioefajardo 6:78494092a326 55 if(action<='5') action++;
julioefajardo 6:78494092a326 56 else action = '1';
julioefajardo 6:78494092a326 57 }
julioefajardo 6:78494092a326 58
julioefajardo 0:f2b89c6a8a16 59 int main() {
julioefajardo 0:f2b89c6a8a16 60 pc.baud(115200); //Serial com at 115200 bauds
julioefajardo 5:49c5553b6e2c 61 pc.attach(&RX_Interrupt); //Serial RX interrupt attachment
julioefajardo 6:78494092a326 62 sw2.rise(&flip);
julioefajardo 4:d8fd3c4484cc 63 EMG_Sampler.attach(&ADC_Sampler, 0.001); //1 ms ticker for ADC Sampler
julioefajardo 5:49c5553b6e2c 64 PWM_Init(); //Servo initialization
julioefajardo 5:49c5553b6e2c 65 myled = 1;
julioefajardo 3:f784301a5166 66
julioefajardo 0:f2b89c6a8a16 67 while(1) {
julioefajardo 0:f2b89c6a8a16 68 if(COCO){
julioefajardo 5:49c5553b6e2c 69 arm_abs_f32(samples, abs_output, 25); //rectifier EMG1
julioefajardo 5:49c5553b6e2c 70 arm_abs_f32(samples2, abs_output2, 25); //rectifier EMG2
julioefajardo 5:49c5553b6e2c 71 arm_abs_f32(samples3, abs_output3, 25); //rectifier EMG3
julioefajardo 5:49c5553b6e2c 72 arm_mean_f32(abs_output, 25, &mean); //mean EMG1
julioefajardo 5:49c5553b6e2c 73 arm_mean_f32(abs_output2, 25, &mean2); //mean EMG2
julioefajardo 5:49c5553b6e2c 74 arm_mean_f32(abs_output3, 25, &mean3); //mean EMG3
julioefajardo 6:78494092a326 75 Serial_Oscilloscope(TRUE,SMOOTH);
julioefajardo 4:d8fd3c4484cc 76 switch(state){
julioefajardo 4:d8fd3c4484cc 77 case 0: {
julioefajardo 5:49c5553b6e2c 78 if (mean>THRESHOLDF){
julioefajardo 4:d8fd3c4484cc 79 myled = 0;
julioefajardo 4:d8fd3c4484cc 80 state = 1;
julioefajardo 5:49c5553b6e2c 81 switch(action){
julioefajardo 5:49c5553b6e2c 82 case '1': FingerPosition(2400, 600, 600,2400,2400); break; //Close
julioefajardo 5:49c5553b6e2c 83 case '2': FingerPosition(2400,2400, 600,2400,2400); break; //Point
julioefajardo 5:49c5553b6e2c 84 case '3': FingerPosition(2400, 600,2400, 600,2400); break; //Pinch
julioefajardo 5:49c5553b6e2c 85 case '4': FingerPosition(2400, 600, 600,2400, 600); break; //Lateral
julioefajardo 5:49c5553b6e2c 86 case '5': FingerPosition(2400, 600, 600, 600,2400); break; //Tripod
julioefajardo 5:49c5553b6e2c 87 default: FingerPosition(2400, 600, 600,2400,2400); //Close
julioefajardo 5:49c5553b6e2c 88 }
julioefajardo 4:d8fd3c4484cc 89 }
julioefajardo 4:d8fd3c4484cc 90 } break;
julioefajardo 4:d8fd3c4484cc 91 case 1: {
julioefajardo 5:49c5553b6e2c 92 if (mean2>THRESHOLDE){
julioefajardo 4:d8fd3c4484cc 93 myled = 1;
julioefajardo 4:d8fd3c4484cc 94 state = 0;
julioefajardo 6:78494092a326 95 FingerPosition(1000,2400,2400, 600, 2400); //Open
julioefajardo 4:d8fd3c4484cc 96 }
julioefajardo 4:d8fd3c4484cc 97 }
julioefajardo 0:f2b89c6a8a16 98 }
julioefajardo 0:f2b89c6a8a16 99 COCO = 0;
julioefajardo 0:f2b89c6a8a16 100 }
julioefajardo 0:f2b89c6a8a16 101 }
julioefajardo 0:f2b89c6a8a16 102 }
julioefajardo 4:d8fd3c4484cc 103
julioefajardo 5:49c5553b6e2c 104 //EMG sampler Ts = 1ms
julioefajardo 4:d8fd3c4484cc 105 void ADC_Sampler() {
julioefajardo 4:d8fd3c4484cc 106 EMG1 = (*3.3f;
julioefajardo 4:d8fd3c4484cc 107 EMG2 = (*3.3f;
julioefajardo 4:d8fd3c4484cc 108 EMG3 = (*3.3f;
julioefajardo 6:78494092a326 109 Serial_Oscilloscope(FALSE,RAW);
julioefajardo 4:d8fd3c4484cc 110 uint32_t m = __get_PRIMASK();
julioefajardo 4:d8fd3c4484cc 111 __disable_irq();
julioefajardo 4:d8fd3c4484cc 112 for(int j=24;j>0;j--) {
julioefajardo 4:d8fd3c4484cc 113 samples[j]=samples[j-1]; //Fill Array
julioefajardo 4:d8fd3c4484cc 114 samples2[j]=samples2[j-1]; //Fill Array
julioefajardo 4:d8fd3c4484cc 115 samples3[j]=samples3[j-1]; //Fill Array
julioefajardo 4:d8fd3c4484cc 116 }
julioefajardo 4:d8fd3c4484cc 117 samples[0]=EMG1;
julioefajardo 4:d8fd3c4484cc 118 samples2[0]=EMG2;
julioefajardo 4:d8fd3c4484cc 119 samples3[0]=EMG3;
julioefajardo 4:d8fd3c4484cc 120 __set_PRIMASK(m);
julioefajardo 4:d8fd3c4484cc 121 COCO = 1;
julioefajardo 4:d8fd3c4484cc 122 }
julioefajardo 4:d8fd3c4484cc 123
julioefajardo 5:49c5553b6e2c 124 //action selection trough serial console
julioefajardo 5:49c5553b6e2c 125 void RX_Interrupt(void){
julioefajardo 5:49c5553b6e2c 126 action = pc.getc();
julioefajardo 5:49c5553b6e2c 127 /*switch(action){
julioefajardo 5:49c5553b6e2c 128 case '1': pc.printf("Power Grip\n"); break;
julioefajardo 5:49c5553b6e2c 129 case '2': pc.printf("Point\n"); break;
julioefajardo 5:49c5553b6e2c 130 case '3': pc.printf("Pinch\n"); break;
julioefajardo 5:49c5553b6e2c 131 case '4': pc.printf("Lateral\n"); break;
julioefajardo 5:49c5553b6e2c 132 case '5': pc.printf("Tripod\n"); break;
julioefajardo 5:49c5553b6e2c 133 default: pc.printf("Power Grip\n");
julioefajardo 5:49c5553b6e2c 134 }*/
julioefajardo 4:d8fd3c4484cc 135 }
julioefajardo 4:d8fd3c4484cc 136
julioefajardo 5:49c5553b6e2c 137 //PWM initialization for servos
julioefajardo 5:49c5553b6e2c 138 void PWM_Init(void){
julioefajardo 5:49c5553b6e2c 139 //Open -> 0.6ms - Close 2.4ms
julioefajardo 6:78494092a326 140 Thumb.period(0.02f);
julioefajardo 6:78494092a326 141 Thumb.pulsewidth(0.0010f);
julioefajardo 5:49c5553b6e2c 142 //Open -> 2.4ms - Close 0.6ms
julioefajardo 6:78494092a326 143 //Index.period(0.02f);
julioefajardo 6:78494092a326 144 Index.pulsewidth(0.0024f);
julioefajardo 5:49c5553b6e2c 145 //Open -> 2.4ms - Close 0.6ms
julioefajardo 6:78494092a326 146 Middle.period(0.02f);
julioefajardo 6:78494092a326 147 Middle.pulsewidth(0.0024f);
julioefajardo 5:49c5553b6e2c 148 //Open -> 0.6ms - Close 2.4ms
julioefajardo 6:78494092a326 149 //Pinky.period(0.02f);
julioefajardo 6:78494092a326 150 Pinky.pulsewidth(0.0006f);
julioefajardo 5:49c5553b6e2c 151 //Open -> 0.6ms - Close 2.4ms
julioefajardo 6:78494092a326 152 ThumbRot.pulsewidth(0.0006f);
julioefajardo 5:49c5553b6e2c 153 }
julioefajardo 5:49c5553b6e2c 154
julioefajardo 5:49c5553b6e2c 155 //send data through serail port for oscilloscope visualization
julioefajardo 5:49c5553b6e2c 156 void Serial_Oscilloscope(uint8_t activation, uint8_t type){
julioefajardo 5:49c5553b6e2c 157 if (activation){
julioefajardo 5:49c5553b6e2c 158 switch(type){
julioefajardo 6:78494092a326 159 case RAW: pc.printf("%.10f,%.10f\n\r",EMG1,EMG2); break;
julioefajardo 6:78494092a326 160 case RECTIFIED: pc.printf("%.10f,%.10f\n\r",abs_output[0],abs_output2[0]);break;
julioefajardo 6:78494092a326 161 case SMOOTH: pc.printf("%.10f,%.10f\n\r",mean,mean2); break;
julioefajardo 6:78494092a326 162 default: pc.printf("%.10f,%.10f\n\r",EMG1,EMG2);
julioefajardo 5:49c5553b6e2c 163 }
julioefajardo 5:49c5553b6e2c 164 }
julioefajardo 5:49c5553b6e2c 165 }
julioefajardo 5:49c5553b6e2c 166
julioefajardo 5:49c5553b6e2c 167 //finger position through servos - values on microseconds (600 us - 2400 us)
julioefajardo 5:49c5553b6e2c 168 void FingerPosition(float32_t thumb_us, float32_t index_us, float32_t middle_us, float32_t pinky_us, float32_t thumbrot_us){
julioefajardo 6:78494092a326 169 Thumb.pulsewidth(thumb_us/1000000.0f);
julioefajardo 6:78494092a326 170 Index.pulsewidth(index_us/1000000.0f);
julioefajardo 6:78494092a326 171 Middle.pulsewidth(middle_us/1000000.0f);
julioefajardo 6:78494092a326 172 Pinky.pulsewidth(pinky_us/1000000.0f);
julioefajardo 6:78494092a326 173 ThumbRot.pulsewidth(thumbrot_us/1000000.0f);
julioefajardo 5:49c5553b6e2c 174 }