sending the structure data using ble_nus_send

[ps_anu]

Hi,

 I want to send the accelerometer data  in a structure  to the mobile app via ble , is it possible ? Any reference 

[awneil]

Just like a real hardware UART, the NUS just sends bytes - it neither knows nor cares anything about data structure or meaning.

So you can either just send the entire struct as a stream of bytes, or pick each field from the struct, and send individually.

For the 1st option, remember that compilers may insert padding ...

[ps_anu]

i tried to pass the structure value in ble_nus_send but failed 

[awneil]

would you care to be a little less vague?

1. Show your code;
2. Explain how, exactly, it "failed".

[ps_anu]

//void mpu_6050_read_acc(int16_t  *p_x_val, int16_t  *p_y_val, int16_t *p_z_val)
char *accel_data()
{
    ret_code_t err_code;
    float *p_a_val;
     float *p_b_val;
      float *p_c_val;
  

      int16_t *p_x_val;
int16_t *p_y_val;
int16_t *p_z_val;
      
    // Raw accelerometer measurements buffer
    uint8_t acc_data[6];
    
    // Read the six accelerometer data registers starting from ACCEL_XOUT_H
    mpu_6050_I2C_register_read(ACCEL_XOUT_H,acc_data,sizeof(acc_data));
    
    APP_ERROR_CHECK(err_code);
    
    /*  Combine the two 8-bit data registers to a 16-bit value
        for each axis by left shifting ACCEL_xOUT_H eight times 
        and OR it with ACCEL_xOUT_L. */

            

 * p_x_val = (acc_data[0]<<8)|acc_data[1];
    *p_y_val = (acc_data[2]<<8)|acc_data[3];
    *p_z_val =  (acc_data[4]<<8)|acc_data[5];


       *p_a_val = (*p_x_val) /16384.0; // in m/s^2
         *p_b_val = (*p_y_val) /16384.0; // in m/s^2

 *p_c_val = (*p_z_val) /16384.0; // in m/s^2
 
        
alt[0]=*p_a_val;
alt[1]=*p_b_val;
alt[2]=*p_c_val;


sprintf(accel,",%.2f,%.2f,%.2f\n",alt[0],alt[1],alt[2]);
return accel;

}
// creating a structure 
struct sensor_data 
{
char timestamp[100];
int sensor_value;
};

struct sensor_data sensordata_array[100];


while(1)


{
 


for (;data_read_counter<100;data_read_counter++)
{
time_stamp_data =nrf_cal_get_time_string(true); //timestamp data in string
acceleromter_data=accelerometer_function_data();// acceleromter data in string
strcat(time_stamp_data,acceleromter_data);
 strcat(sensordata_array[data_read_counter].timestamp,time_stamp_data);

 sensordata_array[data_read_counter].sensor_value=sensor_array[data_read_counter];



nrf_delay_us(6000);

}

for (data_read_counter=0;data_read_counter<100;data_read_counter++)
{

NRF_LOG_INFO("original value:%s", sensordata_array[data_read_counter].timestamp);
NRF_LOG_INFO("original value:%d", sensordata_array[data_read_counter].sensor_value);

nrf_delay_ms(2000);


length=sizeof(sensordata_array[data_read_counter].timestamp);

ble_nus_data_send(&m_nus,sensordata_array[data_read_counter].timestamp,&length,m_conn_handle);
}

}}

I am getting the junk values why even I increased the number of bytes in an array . I don't know how to get the exact the number of bytes please help me 

[ps_anu]

 hi awneil 

I am getting the junk value while I am passing the structure in ble_nus_send . By using  function  printf("Length of String is %lu\n", strlen(timestamp));  I am getting the length of string , even though i am getting junk why ?

struct sensor_data 
{
char timestamp[41]; //  41 by using printf  strlen
int sensor_value;
};

struct sensor_data sensordata_array[10];


while(1)


{




for (;data_read_counter<10;data_read_counter++){
timestamp_data =nrf_cal_get_time_string(true);
sensor_value_data=accel_data();
strcat(timestamp_data,sensor_value_data);
 
 strcat(sensordata_array[data_read_counter].timestamp,timestamp_data);

sensordata_array[data_read_counter].sensor_value=sensor_array[data_read_counter];



nrf_delay_us(8000);

}

for (data_read_counter=0;data_read_counter<10;data_read_counter++)
{

NRF_LOG_INFO("original value:%s", sensordata_array[data_read_counter].timestamp);
NRF_LOG_INFO("original value:%d", sensordata_array[data_read_counter].sensor_value);

nrf_delay_ms(2000);


length=sizeof(sensordata_array[data_read_counter].timestamp);

ble_nus_data_send(&m_nus,sensordata_array[data_read_counter].timestamp,&length,m_conn_handle);

}