Maximum Bytes sent through BLE limited to 20

RE: Maximum Bytes sent through BLE limited to 20

Susheel Nuguru — Thu, 29 Jun 2023 15:35:07 GMT

You have take few things into consideration.

Make sure that you have buffer with enough size to hold the actual data to be transmitted over BLE like Naeem pointed out.
You need to check if the MTU size is correctly set to be able send the 40 bytes of data in the same connection event, See GATTC ATT_MTU Exchange and GATTS ATT_MTU Exchange, sd_ble_cfg_set, sd_ble_gattc_exchange_mtu_request, and sd_ble_gatts_exchange_mtu_reply.
Add some air sniffer to see what data is tranmitted over air and what you are doing to post process that data on the receiving end.

The use case you have is quite simple apart from the difference that you are multiplexing different raw data into one buffer (which is quite ok). I do not see any other complications in what you wanting to achieve.

RE: Maximum Bytes sent through BLE limited to 20

Aarun — Tue, 27 Jun 2023 15:06:50 GMT

Hi,

This is the example I'm using. I simply wish to sample 4 channels (SAADC) at 200Hz and send them over BLE

nRF52-ADC-examples/ble_app_uart__saadc_timer_driven__scan_mode at master · NordicPlayground/nRF52-ADC-examples · GitHub

RE: Maximum Bytes sent through BLE limited to 20

Naeem Maroof — Tue, 27 Jun 2023 13:07:08 GMT

There are few things I could mention related to the code:

[quote user=""] After padding the bytes needed to be sent through a packet is 40 bytes[/quote]

the nus_string is not of size 40

//custom code for sending 2 packet flag in BLE
uint8_t nus_string[]="aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";

In the saadc_callback(), what you are doing here:

else {
    uint8_t nus2[25];
    int i,j;
    sprintf(nus2, "%d %d %d %d! /",p_event->data.done.p_buffer[0],p_event->data.done.p_buffer[1],p_event->data.done.p_buffer[2],p_event->data.done.p_buffer[3]);
    for(i=0;nus_string[i]!='/';i++);   
    for(int j=0;nus2[j]!='/';j++)
    {     
        nus_string[i]=nus2[j];  
        i++;
    } 
    bytes_to_send = sprintf(nus_string, "%s",nus_string);
    err_code = ble_nus_data_send(&m_nus, nus_string, &bytes_to_send, m_conn_handle);
    if ((err_code != NRF_ERROR_INVALID_STATE) && (err_code != NRF_ERROR_NOT_FOUND))
    {
        APP_ERROR_CHECK(err_code);
    }
    m_adc_evt_counter++;
    sprintf(nus_string,"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
}

You have declared nus2 as 25 byte, and you are writing 8 bytes of data (from buffer 0,1,2,3) to the nus2 and some characters?

I think you are trying to copy the contents (data / integers) 2 times into the nus_string. But I think you are not doing it correctly here.

You are putting first copy in the if statement

And you are putting the second copy in the else statement (by first putting data into nus2)

Only one of these statements (if or the else) will be true, and hence you will only have one copy.

Also, why the rest of the code is within else block. I think it should be outside of the if-else.

Best regards,

Naeem

RE: Maximum Bytes sent through BLE limited to 20

Naeem Maroof — Tue, 27 Jun 2023 12:18:12 GMT

Hello,

I am sorry I am not able to understand your code.

I was also not able to compile and test it fully.

I am not sure what you are doing (in code) and how you are testing. Is your code based on some nordic sample.

If you start with a Nordic sample, and then incorporate changes into it and let me know where and what you are changing for your desired outcome, then I can dig into it why it is not working so.

If you are not limited to use older (nrf5) SDK, I suggest you to try Nordic Connect SDK along with VS Code.

Regards,

Naeem

RE: Maximum Bytes sent through BLE limited to 20

Aarun — Fri, 23 Jun 2023 13:56:29 GMT

Sorry, this should work https://drive.google.com/file/d/1TLQHzSahc1JU5fny0WuPiI66_ylOhMNM/view?usp=sharing

RE: Maximum Bytes sent through BLE limited to 20

Naeem Maroof — Fri, 23 Jun 2023 13:32:17 GMT

I am not able to open and compile your project successfully.

I can also see that there is no "main.c" file in the folder you have shared.