bogdan / USB-Meter
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Platform Decision - iOS 15.md
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+# Platform Decision: iOS 15
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+
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+Date: 2026-03-22
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+
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+## Decision
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+
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+Minimum deployment target for the app becomes `iOS 15`.
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+
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+This is the last iOS version supported by `iPhone 6s`, which remains a valid target device for this product:
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+- BLE communication is fully capable on this hardware.
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+- Live data acquisition, diagnostics, and logging are within its capabilities.
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+- Local history and long-term battery tracking are also realistic for the product goals.
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+
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+## Product Goals
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+
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+The application is intended to support:
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+
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+- live data collection for device diagnostics
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+- real battery capacity measurement using USB meters
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+- long-term degradation tracking through historical data
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+- efficiency analysis for charging chains
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+- charger efficiency analysis
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+
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+## Why We Are Leaving iOS 13
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+
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+`iOS 13` is too old for the current development direction:
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+
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+- first-generation SwiftUI requires more workarounds and compatibility code
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+- maintenance and testing cost is higher
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+- newer Xcode / App Store tooling trends are centered around more recent deployment targets
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+
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+Moving to `iOS 15` reduces risk without dropping `iPhone 6s`.
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+
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+## Why We Are Not Moving to iOS 16 Yet
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+`iOS 16` would unlock APIs such as `NavigationStack` and `Swift Charts`, but it would also exclude `iPhone 6s`.
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+At this stage, preserving `iPhone 6s` support is considered more valuable than gaining those APIs.
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+
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+## Charts Decision
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+Current conclusion:
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+- keep the in-house chart solution for live charts
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+- do not adopt `Swift Charts` for the live measurement view
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+- reconsider `Swift Charts` later only for historical reports and analysis screens
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+
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+Reasoning:
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+- `Swift Charts` looks strong for reports and final analysis
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+- it does not appear ideal for high-frequency live updates
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+- zoom and pan would still require custom work
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+- the current in-house renderer gives better control for instrument-style live views
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+
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+## Device Coverage Notes
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+Choosing `iOS 15` preserves `iPhone 6s` support.
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+There are also older iPads that remain on `iPadOS 15`. Apple security release notes for January 26, 2026 still list devices such as:
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+- `iPad Air 2`
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+- `iPad mini 4`
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+So this platform decision likely preserves some older iPad coverage as well.
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+
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+## Revisit Trigger
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+We should revisit the minimum deployment target when one of the following becomes important:
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+- a strong need for `Swift Charts`
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+- a move toward `SwiftData` / more modern SwiftUI app architecture
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+- loss of business value in keeping `iPhone 6s` support
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+- support or distribution constraints imposed by newer Xcode / App Store requirements
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+
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+## References
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+- Apple Xcode system requirements: https://developer.apple.com/xcode/system-requirements/
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+- Apple upcoming App Store requirements: https://developer.apple.com/news/upcoming-requirements/
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+- Apple App Store platform usage: https://developer.apple.com/support/app-store/
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+- Apple security releases: https://support.apple.com/en-lamr/100100
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USB Meter.xcodeproj/project.pbxproj
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@@ -182,6 +183,7 @@
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 			isa = PBXGroup;
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 			children = (
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+				1C6B6B8A2A2D4F5100A0B001 /* Platform Decision - iOS 15.md */,
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 				437AEE1424249AAA0025C373 /* Readme.rtf */,
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 				43CBF65E240BF3EB00255B8B /* USB Meter */,
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 				43CBF65D240BF3EB00255B8B /* Products */,
 
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 				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
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 				GCC_WARN_UNUSED_FUNCTION = YES;
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 				GCC_WARN_UNUSED_VARIABLE = YES;
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-				IPHONEOS_DEPLOYMENT_TARGET = 13.0;
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+				IPHONEOS_DEPLOYMENT_TARGET = 15.0;
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 				MTL_ENABLE_DEBUG_INFO = INCLUDE_SOURCE;
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 				MTL_FAST_MATH = YES;
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 				ONLY_ACTIVE_ARCH = YES;
 
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 				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
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 				GCC_WARN_UNUSED_FUNCTION = YES;
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 				GCC_WARN_UNUSED_VARIABLE = YES;
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-				IPHONEOS_DEPLOYMENT_TARGET = 13.0;
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+				IPHONEOS_DEPLOYMENT_TARGET = 15.0;
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 				MTL_ENABLE_DEBUG_INFO = NO;
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 				MTL_FAST_MATH = YES;
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 				SDKROOT = iphoneos;
 

              

          

    

  


  








  

    

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