I am using a Raspberry Pi 5 (BLE 5.0) to read sensor data and send it via D-Bus and BlueZ to a Flutter application (flutter_blue_plus) for both iOS and Android. The goal is to display these real-time sensor updates directly on the device.
On Android, the data transmission is immediate and the real-time visualization is extremely smooth and fast. However, on iOS, both BLE write and notification commands appear with noticeable latency—not only in real-time displays, but also when comparing ordinary notification feedback between the Raspberry Pi terminal and the iOS app. It seems that iOS buffers several BLE packets internally and then dispatches them in batches, which always introduces an additional delay.
Additional setup details:
I sample and transmit data every 25ms, sending binary packets of 20 bytes (length shouldn’t be a limiting factor).
On the iOS side I am using an iPhone 15 Pro with iOS 18.6.2 (BLE 5.3).
The Raspberry Pi (using btmon for logging) confirms after connection setup that the connection interval is fixed at 30ms (and cannot be changed).
I have tried sending BLE packets every 30ms so that exactly one packet arrives per interval, but this made no difference—the latency and batch delivery remain.
Interestingly, faster transmission rates (e.g. sending every 10ms) make the real-time display look smoother on iOS, but the guaranteed overall system latency does not improve.
Also these methods used: write-without-response, using app in release modus (no debugging)
Is there anyone familiar with this problem or a potential solution? Or is iOS simply not optimized for true real-time BLE data streaming and visualization? Any pointers, technical insights or workarounds would be greatly appreciated.