Waveform is a workbench iOS application that illustrates scaffolding to retrieve and display time series data streams.
The initial implementation is focused on handling Electrocardiogram signals - querying for and displaying one signal.
The ECG time series are queried from a the HealthKit store, Apple Watch captured.
The user interface under construction is illustrated below, with the iPhone rotated 90 degrees to illustrate the strip mode presentation of the plot.
| Waveform |
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The rough blueprint for key areas in the iOS application system are as follows:
- Type System
- Providers
- Adapters
- Algorithms
- Views
The Providers represents building blocks, roughly aligned with CQRS such as Readers or Writers or interfaces that package underlying application logic.
The Adapters layer provides the interface encapsulation around the HealthKit calls, primarily read only query paths in this vertical.
There is Algorithm code with implementations in both the Swift and C++ languages with a focus on time series signal analysis ECG time series voltage readings.
Large portions of this code is from my previous work iterations over time - scrubbed and evolved forward to refine, but largely kept intact. In past projects in select concept proof verticals, there potentially was Objective-C code (logic or user interface) - but the current stack is Swift and C++ with primarily SwiftUI instead of UIKit at this juncture.
Note that way back, in a sports medicine context, I had implemented an HRV implementation before Apple added one native to Health APP. My approach back then was based on Root Mean Square of Successive Deviations (RMSSD); code parked but a cleaned up version exists.
The sample type HKElectrocardiogram representing the ECG voltage signals in HealthKit is used intact, as is in this particular vertical.
Apple Developer Documentation: HKElectrocardiogram
The rest of the source code is under the MIT License as per below:
MIT License
Copyright (c) 2025 John Matthew Weston
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