BLE project essentials
- BLE is the default for phone-paired devices. It works with iOS and Android without a gateway and can run for months or years on a coin cell.
- Battery life is set by connection parameters and advertising intervals, not by the chip alone. Tuning them correctly commonly makes a several-fold difference to battery life.
- Interoperability is the hard part. The same firmware can behave differently across phone models, so testing on real devices is non-negotiable.
- Hexcode Plus delivers firmware, hardware and integration, including the GATT profile your mobile developers will code against.
Platforms we use for BLE
- Nordic nRF52 series with the nRF Connect SDK (Zephyr based) when battery life and a polished BLE stack matter most.
- ESP32-C3 and ESP32-S3 when Wi-Fi and BLE are both needed and cost matters.
- STM32WB when you want BLE inside the STM32 ecosystem.
- Silicon Labs and other vendors where the customer already has a supply relationship.
Designing the GATT profile
The GATT profile is the contract between firmware and app. A poorly designed profile forces both teams to rewrite later. We define services and characteristics early, choose standard Bluetooth SIG profiles where one fits (for example battery or heart-rate services), use custom 128-bit UUIDs where it does not, and document properties, notification behaviour and data formats in a one-page interface spec.
Keeping payloads within the negotiated ATT MTU avoids fragmentation, and notifications are preferred over polling to save power.
Low-power tuning
| Setting | Effect on the product |
|---|---|
| Advertising interval | Longer interval saves battery but slows discovery |
| Connection interval | Longer interval saves battery but adds latency |
| Peripheral latency | Lets the device skip connection events when it has nothing to send |
| TX power | Lower power saves energy but reduces range |
| PHY selection | 2M PHY shortens airtime; coded PHY extends range |
We measure real current with a power analyser across advertising, connected idle and active states, then tune against your battery-life target.
Phone interoperability and updates
We test pairing, bonding, reconnection and background behaviour on a representative set of Android and iOS phones, because behaviour varies. Firmware updates over BLE use a signed image and a dual-bank or swap scheme so an interrupted update cannot brick the device. For a Bluetooth-branded product you must also go through Bluetooth SIG qualification; we advise on that early. See also certification in India.
Sources and further reading
- Bluetooth SIG — Specifications, assigned numbers and qualification process.
- Nordic Semiconductor documentation — nRF Connect SDK and nRF52 series reference material.
- Zephyr Project documentation — The RTOS underlying the nRF Connect SDK.
Last reviewed: October 2026. Regulations and product availability change; confirm current rules with the issuing authority before you commit to a design.