The first version used the vendor's cloud API, which worked but bothered me: my inverter is 10 meters away, why is my data doing a round trip through a server in China? So I added local Modbus TCP support. The app now talks directly to the inverter's datalogger over the LAN, no cloud account needed, works when the internet is down, and updates are near-instant instead of the 5-minute cloud polling interval. (Still I'm limited by around 15 min iOS Widget polling)

Some things that turned out to be harder than expected:

Writing a Modbus TCP client in Swift with Network.framework. There isn't much prior art for Modbus on iOS, and dataloggers are picky — some drop connections if you poll too aggressively, some only accept one concurrent client.

Register maps. Every vendor (and sometimes every firmware revision) lays out registers differently power values as 32-bit across two registers, inconsistent signedness for import/export, scaling factors that differ between models. A lot of the work is a growing library of per-model register definitions. I've already received some good feedback from other than Solis users that tried that app. Once I'll get more valuable feedback I could extend list of supported Inverters. Although it's all depend if Modbus is available.

WidgetKit's refresh budget. iOS gives widgets a limited number of refreshes per day, which is fundamentally at odds with "live" energy data. I ended up with around 15 min invervals.

I've also added recently GameCenter support, so now everyone can compare their installations and how it works with other (fair algorithms are included so small good positioned installation beats bigger)

It's a paid app - but basic usage (no live widget support) are free.

Comments URL: https://news.ycombinator.com/item?id=48860904

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