How to send more than 20 bytes using sd_ble_gatts_hvx

[valdev]

Hello,

I am looking for a way to send more than 20 bytes by using 'sd_ble_gatts_hvx' function. I want to get the maximum debit that is in theory 6x20 bytes Do I just have to send the set the p_len parameter to 6x20, because i didn't succeed through this way! I am using the S110 firmware and the nRF51-Dongle Thanks for you help

[Petter Myhre]

It is well described here.

Edit 16.10.2015

The point is that you can notify maximum 20 bytes with each call to sd_ble_gatts_hvx().

So you call this in a loop until it returns BLE_ERROR_NO_TX_BUFFERS, then you break out of the loop. Then you will get the BLE_EVT_TX_COMPLETE event when one or more packets have been sent. So then you loop sd_ble_gatts_hvx() again until you get BLE_ERROR_NO_TX_BUFFERS, and so on.

If you do this with the S110 you can get 6 packets in each connection interval because the TX buffer size is 6 (if the central device supports it).

[valdev]

Here a part of my code:

attr_char_value.init_len= attr_char_value.max_len=20*6;
attr_char_value.p_value   = encoded_initial_hrm;  where encoded_initial_hrm points a 20*6 byte vector

I do a loop like as following if (p_hrs->conn_handle != BLE_CONN_HANDLE_INVALID):

uint8_t i_packet=0; // variable to count the while increment
uint8_t i_NRF_SUCCESS=0; // variable to count NRF_SUCCESS event
hvx_params.handle = p_hrs->sequence0_handles.value_handle;
hvx_params.type   = BLE_GATT_HVX_NOTIFICATION; 
hvx_params.offset = 0;
hvx_params.p_len  = &hvx_len;
hvx_params.p_data = encoded_hrm1;	
while(1)
{
err_code0 = sd_ble_gatts_hvx(p_hrs->conn_handle, &hvx_params);
i_packet++;
if (err_code0==NRF_SUCCESS) // only to count NRF_SUCCESS event
{							
i_NRF_SUCCESS++;		
NULL;
}
if (err_code0==BLE_ERROR_NO_TX_BUFFERS)
{
break; 
}
else
if(err_code0 == NRF_ERROR_INVALID_STATE || err_code0 == BLE_ERROR_GATTS_SYS_ATTR_MISSING)	
{
break;
}
previous_err_code0=err_code0;
}

That I see is I get an NRf_SUCCESS after my first sd_ble_gatts_hvx(...) call and after the second one I get already BLE_ERROR_NO_TX_BUFFERS. For me it seems that I only sent 20bytes and not 6x20bytes. Because when I get the ‘break’ because of the err_code0==BLE_ERROR_NO_TX_BUFFERS, I have i_NRF_SUCCESS =1 and i_packet=2; So I didn’t fill the TX BUFFER with 20x6 bytes... so how I can I be sure that by TX BUFFER is full of 20x6 bytes?