How to use "ble_nus_string_send correctly" ?

Question

Hello everybody, I try to send nus_string data. I bought different inputs and outputs like this; 
 INPUT; 
 
 while(ble_nus_string_send(&m_nus, (uint8_t *)"aaaaaaaaaaaaaaa", (uint16_t *)17) != NRF_SUCCESS); // I wrote "a" 17 times

OUTPUT; 
 "aaaaa" received // Send 5 times "a" 
 
 INPUT; 
 
 while(ble_nus_string_send(&m_nus, (uint8_t *)"aaaaaaaaaaaaaaaaa", (uint16_t *)19) != NRF_SUCCESS); //I wrote "a" 19 times

 
 OUTPUT; 
 There is no response! 
 
 1-Why do I see 5 characters when I enter 17 characters? 
 2-Why do not I see anything when I enter 19 characters? 
 3-How do I enter any characters and see all of it? 
 
 Thank you :)

Kenneth · Accepted Answer

Try this: 
 APP_TIMER_DEF(send_some_uart_data); /**< Some timer */

void send_some_uart_data_handler(void * p_context)
{
 ret_code_t err_code;
 
 uint8_t string[] = "serial updated
";
 uint16_t length = sizeof(string);
 
 do
 {
 
 err_code = ble_nus_string_send(&m_nus, string, &length);
 if ( (err_code != NRF_ERROR_INVALID_STATE) && (err_code != NRF_ERROR_BUSY) )
 {
 APP_ERROR_CHECK(err_code);
 }
 } while (err_code == NRF_ERROR_BUSY); 
}

void send_some_data_uart_init(void)
{
 app_timer_create(&send_some_uart_data,APP_TIMER_MODE_REPEATED, send_some_uart_data_handler);
 app_timer_start(send_some_uart_data, APP_TIMER_TICKS(1000), NULL);
}

// Call send_some_data_uart_init(); in main() to run send_some_uart_data_handler() at configured internal.

hmolesworth · Answer

In addition to the other points, (uint16_t *)17 doesn't do what you think. It actually indicates the contents of physical memory address 17. Not surprisingly the byte contents of physical address 17 is likely 5. So instead use a variable thus: 
 uint16_t someLength = 17;
blahBlah, &somelength, BlahBlah
or better
uint16_t someLength = sizeof(whatever);
blahBlah, &somelength, BlahBlah
or better for strings
nt16_t someLength = strlen("whatever dude");
blahBlah, &somelength, BlahBlah

How to use "ble_nus_string_send correctly" ?

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