BLE Connection Parameters Cheatsheet

Quick reference for the three core BLE connection parameters and the trade-offs between power, latency, and throughput.

The three parameters

Connection Interval (connInterval)

Time between the start of two consecutive connection events. Range: 7.5 ms – 4 s (multiples of 1.25 ms).

• Short interval (7.5–50 ms) — low latency, high throughput, high power
• Long interval (500 ms–4 s) — low power, high latency, suits sensor beacons

Slave Latency (connSlaveLatency)

Number of connection events the peripheral can skip while it has no data to send. Range: 0–499.

• Effective interval = connInterval × (slaveLatency + 1)
• Use to extend sleep time without disconnecting when there's nothing to transmit
• Central still wakes every interval; only the peripheral skips

Supervision Timeout (connSupervisionTimeout)

Maximum time without a successful connection event before the link is considered lost. Range: 100 ms – 32 s (multiples of 10 ms).

Constraint: supervisionTimeout > (1 + slaveLatency) × connInterval × 2

Common configurations

| Use case | Interval | Slave latency | Timeout | Notes | |---|---|---|---|---| | HID (keyboard/mouse) | 7.5–15 ms | 0 | 2 s | Latency-critical | | Audio streaming | 7.5–20 ms | 0 | 2–5 s | Throughput-critical | | Health sensor | 100–500 ms | 3–9 | 5–10 s | Balanced | | Environmental sensor | 1–2 s | 0 | 10–20 s | Power-optimized | | Asset tracker | 2–4 s | 0 | 30 s | Minimum power |

Power impact

Current draw scales roughly linearly with connection event frequency. A device running at 15 ms interval with 0 slave latency wakes ~67× per second vs. 7× at 140 ms effective interval (15 ms × (8+1)).

For coin-cell devices, target an effective interval ≥ 500 ms and keep connection time short — connect, transfer, disconnect.

iOS and Android constraints

• iOS enforces minimum interval of 15 ms for most apps; 7.5 ms requires specific entitlements
• Android behavior varies by chipset — test on at least 3 devices
• Both platforms may renegotiate connection parameters; implement SMP_SLAVE_PREFERRED_PARAMS to signal preferences