send data over uart without losing connection

[Deepak Kumar]

hi all, i have a electronic device having a button which sends continous data till i keep button pressed. i want to send these data without losing connection. i can across this tutorial where it is written that i can send data using ble_nus_c_string_send() function this function can only be used 2 times per connection interval (minimum 7.5 ms). If I call this function too fast, the tx buffers fill up and you will be returned the error BLE_ERROR_NO_TX_BUFFERS.

how i should handle this situation so that if i keep my button pressed which gives multiple data and need to send data without connection lost.

Please kindly guide me with some example or something.

thanks!!

[awneil]

You need a buffer (or "queue") to hold the data that's awaiting transmission.

[Christopher]

Many users already asked for you problem (see here some search results). Here is a Nordic's answer, and here is another one.

As described here, you can send up to 20 bytes in each notification packets. Depending on the SoftDevice you use, you can send one or more BLE packets per connection interval.

To send a large chunk of data, you have to use the BLE_EVT_TX_COMPLETE event. A simple solution consist of sending as many bytes as you can until you get the BLE_ERROR_NO_TX_BUFFERS, and then wait for the BLE_EVT_TX_COMPLETE event to send again as much as data as you can. Another solution consist of tracking the number of available TX buffers/packets (using p_ble_evt->evt.common_evt.params.tx_complete.count).