How to transmit 6 packets in S130 Uart central

Question

Hi there, 
 I am struct for two days trying to send 6 packets of 20 bytes as central. I use ble app uart central sample from nrf5_sdk11.0 with nrf51 S130 v2.0 softdevice. 
 I start believing that this sample and softdevice can only transmit 3 packets per connection interval. As I debug in the central side, it can only execute write command with out response 3 times then a buffer full occurs. When I get the sd_ble_tx_packet_count_get during connection it is only 3. I expect that is 6...for 6 tx? I also monitor the write event in the peripheral side I can only get 3 write interrupt. 
 I try to use the sd_ble_opt_set(BLE_COMMON_OPT_CONN_BW, &ble_opt) setting the tx and rx bandwidth to BLE_CONN_BW_HIGH but won't work out. I use this API during stack initialization and also right after sd_ble_gap_connect. It seems it only accept BLE_CONN_BW_MID 
 What would be my configuration to make to transmit 6 packets per connection interval. My connection interval is only 100msec and using S310 version 3.0 in the peripheral side. 
 Thank you for helping me out.
-Mc

RK · Accepted Answer

Are you actually configuring the BLE stack when you initialise it to have available high bandwidth central connections? the sd_ble_opt_set() is used to tell the softdevice on a per-connection basis which of the configured bandwidths to use, but if you haven't allocated any high-bandwidth central connections when you enabled the softdevice in the first place, there aren't any available. 
 Post the code you're using to set up the parameters for sd_ble_enable(), that's where you have to initially configure the SD to have the connections you want.

How to transmit 6 packets in S130 Uart central

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