低功耗蓝牙里重要的三个连接参数：Connection Interval,Slave Latency,Supervision Timeout.这三个参数决定了BLE的功耗。
更新连接参数的相关api：
// Update cnx parameters
if (((struct gap_le_create_conn_req_cmp_evt *)param)->conn_info.con_interval < GAP_PPCP_CONN_INTV_MIN)
{
// Update connection parameters here
struct gap_conn_param_update conn_par;
/// Connection interval minimum
conn_par.intv_min = GAP_PPCP_CONN_INTV_MIN;
/// Connection interval maximum
conn_par.intv_max = GAP_PPCP_CONN_INTV_MAX;
/// Latency
conn_par.latency = GAP_PPCP_SLAVE_LATENCY;
/// Supervision timeout, Time = N * 10 msec
conn_par.time_out = GAP_PPCP_STO_MULT;
app_gap_param_update_req(((struct gap_le_create_conn_req_cmp_evt *)param)->conn_info.conhdl, &conn_par);
}
ios app连接时，apple公司有自己的规范，这三个参数的设置必须在其规范内才可生效：
● Interval Max * (Slave Latency + 1) ≤ 2 seconds
● Interval Min ≥ 20 ms
● Interval Min + 20 ms ≤ Interval Max Slave Latency ≤ 4
● connSupervisionTimeout ≤ 6 seconds
● Interval Max * (Slave Latency + 1) * 3 < connSupervisionTimeout