How to send simple string data ?

Question

I am receiving data from a phone, i want to send back a word . 
 So , this is probably wrong but , to send : 
 void sendBluetoothData( uint8_t data[], uint16_t length)
 {
 uint32_t err_code;
 static uint8_t data_array[BLE_NUS_MAX_DATA_LEN];
 err_code = ble_nus_string_send(&m_nus, data, length);
 if ( (err_code != NRF_ERROR_INVALID_STATE) && (err_code != NRF_ERROR_BUSY) )
 {
 //APP_ERROR_CHECK(err_code);
 }
 }
 
 and use it with : 
 uint8_t tosend[5];
 tosend[0]=7;
 tosend[1]=2;
 tosend[2]=7;
 tosend[3]=6;
 sendBluetoothData(tosend,4);
 
 I think it sends 0 twice back to the phone. 
 How should I re-write this function to send strings out ? 
 (using SDK 13 with the uart example which I try to write by my self)

erltot · Accepted Answer

This is from the ble_peripheral/ble_app_uart example in SDK 12.2 in my case, I guess it's not very different from SDK13. 
 Simple equivalent of hello world: 
 /**@snippet [Handling the data received over BLE] */
static void nus_data_handler(ble_nus_t * p_nus, uint8_t * p_data, uint16_t length){
 if(p_data[0] == '?'){
 unsigned char data_arr[20] = {"Hello world!	-Pong!
"}; // 20 byte msg
 ble_nus_string_send(&m_nus, data_arr, 20);
 }
}
 
 p_data[0] contains the first character in whatever you recieved from your phone, in this case if it's a "?" it replies with a string.. 
 I prefer to use nRF Toolbox on my iphone with the UART profile for testing 
 From here it was fairly easy to go to strtok() and compare strings/characters in switches to handle incomming text, it's not so pretty but it works. 
 Screenshot from phone:

How to send simple string data ?

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