ECG data acquisition with Analog device frontend and Redbear nano BLE

Dependencies:   BLE_API mbed nRF51822

Fork of BLENano_SimpleControls by RedBearLab

Reference Design

2 channel EKG with Redbear BLE reference and Analog Device amplifier to generate RAW EKG data fed into Medtrics MaaS service . Medtrics API can consumer raw input with given parameters of ADC sample frequency and scaling factor

Specification

  • Application Processor: nRF51822/BLE , Analog frontend: AD8232 /
  • Input Analog Voltage = 3.3V
  • 10 bit ADC input range = (0-1023) or scaling factor= 3.22mV/unit (this is ADC resolution)
  • ADC sample frequency (BLE pull rate) = 250Hz (4ms per sample)

/media/uploads/pkweitai/ble_-3-.jpg Reference IOS and Android app will be online soon!

main.cpp

Committer:
RedBearLab
Date:
2016-01-07
Revision:
3:f530ca03e014
Parent:
2:3cd654f42efa
Child:
4:b95d3432a495

File content as of revision 3:f530ca03e014:

/*

Copyright (c) 2012-2014 RedBearLab

Permission is hereby granted, free of charge, to any person obtaining a copy of this software 
and associated documentation files (the "Software"), to deal in the Software without restriction, 
including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, 
and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, 
subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, 
INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR 
PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE 
FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

*/

#include "mbed.h"
#include "ble/BLE.h"
#include "Servo.h"


#define BLE_UUID_TXRX_SERVICE            0x0000 /**< The UUID of the Nordic UART Service. */
#define BLE_UUID_TX_CHARACTERISTIC       0x0002 /**< The UUID of the TX Characteristic. */
#define BLE_UUIDS_RX_CHARACTERISTIC      0x0003 /**< The UUID of the RX Characteristic. */

#define TXRX_BUF_LEN                     20

#define DIGITAL_OUT_PIN                  P0_9       //TXD
#define DIGITAL_IN_PIN                   P0_10      //CTS
#define PWM_PIN                          P0_11      //RXD
#define SERVO_PIN                        P0_8       //RTS
#define ANALOG_IN_PIN                    P0_4       //P04

BLE             ble;

DigitalOut      LED_SET(DIGITAL_OUT_PIN);
DigitalIn       BUTTON(DIGITAL_IN_PIN);
PwmOut          PWM(PWM_PIN);
AnalogIn        ANALOG(ANALOG_IN_PIN);
Servo           MYSERVO(SERVO_PIN);

//Serial pc(USBTX, USBRX);

static uint8_t analog_enabled = 0;
static uint8_t old_state = 0;

// The Nordic UART Service
static const uint8_t uart_base_uuid[] = {0x71, 0x3D, 0, 0, 0x50, 0x3E, 0x4C, 0x75, 0xBA, 0x94, 0x31, 0x48, 0xF1, 0x8D, 0x94, 0x1E};
static const uint8_t uart_tx_uuid[]   = {0x71, 0x3D, 0, 3, 0x50, 0x3E, 0x4C, 0x75, 0xBA, 0x94, 0x31, 0x48, 0xF1, 0x8D, 0x94, 0x1E};
static const uint8_t uart_rx_uuid[]   = {0x71, 0x3D, 0, 2, 0x50, 0x3E, 0x4C, 0x75, 0xBA, 0x94, 0x31, 0x48, 0xF1, 0x8D, 0x94, 0x1E};
static const uint8_t uart_base_uuid_rev[] = {0x1E, 0x94, 0x8D, 0xF1, 0x48, 0x31, 0x94, 0xBA, 0x75, 0x4C, 0x3E, 0x50, 0, 0, 0x3D, 0x71};


uint8_t txPayload[TXRX_BUF_LEN] = {0,};
uint8_t rxPayload[TXRX_BUF_LEN] = {0,};

//static uint8_t rx_buf[TXRX_BUF_LEN];
//static uint8_t rx_len=0;


GattCharacteristic  txCharacteristic (uart_tx_uuid, txPayload, 1, TXRX_BUF_LEN, GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_WRITE | GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_WRITE_WITHOUT_RESPONSE);
                                      
GattCharacteristic  rxCharacteristic (uart_rx_uuid, rxPayload, 1, TXRX_BUF_LEN, GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_NOTIFY);
                                      
GattCharacteristic *uartChars[] = {&txCharacteristic, &rxCharacteristic};

GattService         uartService(uart_base_uuid, uartChars, sizeof(uartChars) / sizeof(GattCharacteristic *));



void disconnectionCallback(const Gap::DisconnectionCallbackParams_t *params)
{
    //pc.printf("Disconnected \r\n");
    //pc.printf("Restart advertising \r\n");
    ble.gap().startAdvertising();
}

void WrittenHandler(const GattWriteCallbackParams *Handler)
{   
    uint8_t buf[TXRX_BUF_LEN];
    uint16_t bytesRead;
    
    if (Handler->handle == txCharacteristic.getValueAttribute().getHandle()) 
    {
        ble.readCharacteristicValue(txCharacteristic.getValueAttribute().getHandle(), buf, &bytesRead);
        memset(txPayload, 0, TXRX_BUF_LEN);
        memcpy(txPayload, buf, TXRX_BUF_LEN);       
        
        //for(index=0; index<bytesRead; index++)
            //pc.putc(buf[index]);
            
        if(buf[0] == 0x01)
        {
            if(buf[1] == 0x01)
                LED_SET = 1;
            else
                LED_SET = 0;    
        }
        else if(buf[0] == 0xA0)
        {
            if(buf[1] == 0x01)
                analog_enabled = 1;
            else
                analog_enabled = 0;
        }
        else if(buf[0] == 0x02)
        {
            float value = (float)buf[1]/255;
            PWM = value;
        }
        else if(buf[0] == 0x03)
        {
            MYSERVO.write(buf[1]);
        }
        else if(buf[0] == 0x04)
        {
            analog_enabled = 0;
            PWM = 0;
            MYSERVO.write(0);
            LED_SET = 0;
            old_state = 0;    
        }

    }
}
/*
void uartCB(void)
{   
    while(pc.readable())    
    {
        rx_buf[rx_len++] = pc.getc();    
        if(rx_len>=20 || rx_buf[rx_len-1]=='\0' || rx_buf[rx_len-1]=='\n')
        {
            ble.updateCharacteristicValue(rxCharacteristic.getValueAttribute().getHandle(), rx_buf, rx_len); 
            pc.printf("RecHandler \r\n");
            pc.printf("Length: ");
            pc.putc(rx_len);
            pc.printf("\r\n");
            rx_len = 0;
            break;
        }
    }
}
*/
void m_status_check_handle(void)
{   
    uint8_t buf[3];
    if (analog_enabled)  // if analog reading enabled
    {
        // Read and send out
        float s = ANALOG;
        uint16_t value = s*1024; 
        buf[0] = (0x0B);
        buf[1] = (value >> 8);
        buf[2] = (value);
        ble.updateCharacteristicValue(rxCharacteristic.getValueAttribute().getHandle(), buf, 3); 
    }
    
    // If digital in changes, report the state
    if (BUTTON != old_state)
    {
        old_state = BUTTON;
        
        if (BUTTON == 1)
        {
            buf[0] = (0x0A);
            buf[1] = (0x01);
            buf[2] = (0x00);    
            ble.updateCharacteristicValue(rxCharacteristic.getValueAttribute().getHandle(), buf, 3); 
        }
        else
        {
            buf[0] = (0x0A);
            buf[1] = (0x00);
            buf[2] = (0x00);
           ble.updateCharacteristicValue(rxCharacteristic.getValueAttribute().getHandle(), buf, 3); 
        }
    }
}


int main(void)
{   
    Ticker ticker;
    ticker.attach_us(m_status_check_handle, 200000);
    
    ble.init();
    ble.onDisconnection(disconnectionCallback);
    ble.onDataWritten(WrittenHandler);  
    
    //pc.baud(9600);
    //pc.printf("SimpleChat Init \r\n");

    //pc.attach( uartCB , pc.RxIrq);
    
    // setup advertising 
    ble.accumulateAdvertisingPayload(GapAdvertisingData::BREDR_NOT_SUPPORTED);
    ble.setAdvertisingType(GapAdvertisingParams::ADV_CONNECTABLE_UNDIRECTED);
    ble.accumulateAdvertisingPayload(GapAdvertisingData::SHORTENED_LOCAL_NAME,
                                    (const uint8_t *)"Biscuit", sizeof("Biscuit") - 1);
    ble.accumulateAdvertisingPayload(GapAdvertisingData::COMPLETE_LIST_128BIT_SERVICE_IDS,
                                    (const uint8_t *)uart_base_uuid_rev, sizeof(uart_base_uuid));
    // 100ms; in multiples of 0.625ms. 
    ble.setAdvertisingInterval(160);

    ble.addService(uartService);
    
    ble.startAdvertising(); 
    
    //pc.printf("Advertising Start \r\n");
    
    while(1)
    {
        ble.waitForEvent(); 
    }
}