Zephyr Connectivity: BLE

Implement robust, low-power Bluetooth Low Energy applications using Zephyr's industry-standard BLE stack.

Core Workflows

1. BLE Fundamentals

Set up advertising, define GATT services, and manage connections.

• Reference: [ble_fundamentals.md](references/ble_fundamentals.md)
• Key Tools: BT_GATT_SERVICE_DEFINE, bt_le_adv_start, BT_CONN_CB_DEFINE.

2. Send-When-Idle Pattern

Optimize radio usage by bundling data and transmitting only during idle periods.

• Reference: [send_when_idle.md](references/send_when_idle.md)
• Key Tools: k_work_delayable, Workqueues, SMF integration.

3. Power Optimization

Fine-tune intervals and connection parameters for maximum battery life.

• Reference: [power_optimization.md](references/power_optimization.md)
• Key Tools: bt_le_conn_param, Advertising intervals, PHY selection.

Quick Start (Advertising)

CONFIG_BT=y
CONFIG_BT_PERIPHERAL=y

#include <zephyr/bluetooth/bluetooth.h>

void start_simple_adv(void) {
    bt_enable(NULL);
    bt_le_adv_start(BT_LE_ADV_CONN_NAME, NULL, 0, NULL, 0);
}

Professional Patterns (Wireless Design)

• Aggressive Latency: Increase peripheral latency to allow the radio to stay off longer during quiet periods.
• Decoupled Messaging: Use Zbus to feed data into the BLE module, keeping the radio logic separate from the application logic.
• Idle Bundling: Use the "Send-When-Idle" pattern specifically to reduce the number of wake-ups for the radio controller.

Automation Tools

• [ble_timing_helper.py](scripts/ble_timing_helper.py): Convert advertising/connection intervals from ms to BLE timing units.

Examples & Templates

• [gatt_service_template.c](assets/gatt_service_template.c): Starter custom GATT service definition.

Validation Checklist

• [ ] Device advertises with expected name/flags and is discoverable by a BLE scanner.
• [ ] Central can connect, exchange GATT data, and disconnect without stack errors.
• [ ] Configured connection parameters are reflected after negotiation.
• [ ] Send-When-Idle flow batches traffic instead of transmitting every sample immediately.

Resources

• [References](references/):
• ble_fundamentals.md: GATT, GAP, and connection basics.
• send_when_idle.md: Implementing the idle-bundle pattern.
• power_optimization.md: Parameter tuning and power-saving Kconfigs.
• [Scripts](scripts/):
• ble_timing_helper.py: BLE interval conversion helper.
• [Assets](assets/):
• gatt_service_template.c: Custom service template for GATT.