current optimisation in terms of conn interval and slave latency

Question

Hi 
 
 which is better for reduced current consumption 
 1. lesser value of of MIN_CONN_INTERVAL, MAX_CONN_INTERVAL with large SLAVE_LATENCY 
 2. or vice versa 
 
 Thanks.

hmolesworth · Answer

Seems we are all after the same goal :-) My notes so far, indicating "Write Command" is preferable for improved throughput and implicit lower power consumption since repeated receive packet processing is avoided: 
 // BLE Packet Transmission
// =======================
// Packet format - see Bluetooth 5.0 spec (was Vol 6, Part B, Section 2.2)
// https://www.bluetooth.com/specifications/bluetooth-core-specification
//
// BLE packets are sent ping-pong fashion, with maximum throughput occurring when Master->Slave
// packets have no payload
// Packets are separated by the Inter Frame Space (IFS) of 150uSecs
// Note - MIC Encryption field adds 4 bytes, included in timings below
//
// Connection interval: Determines how often the Central queries data from the Peripheral.
// Peripheral may request an update between between minimum 7.5 ms and maximum 4 sec
// Slave latency: A Non-zero slave latency allows the Peripheral to not answer when the
// Central asks for data up to the slave latency number of times. However if the Peripheral
// has data to send it can send data at any time. This enables a peripheral to stay sleeping
// for a longer time, if it doesn't have data to send, but still send data fast if needed
// Connection Supervision Timeout: Determines the timeout from the last data exchange untill
// a link is considered lost. A Central will not start trying to reconnect before the timeout
// has passed, so a short timeout is preferred for devices often going out of range
//
// "Write Command" is a write without acknowledgement and "Write Request" is write with acknowledgement.
// The ATT will automatically send ack when you transmit write request from the central device. Write
// Command on the client side should generate BLE_GATTS_EVT_WRITE(WRITE_CMD, data) event on the server
//
// An integral number of packets can be sent in each connection interval. Shortest interval
// is 7.5mSecs, longest 4,000mSecs in steps of 1.25mSecs