![]() When it hits the target ceiling of 85☌ that icon is replaced by one with full bar of red, and the firmware becomes more aggressive throttling things down to stay below 85☌. When temperature rises above 80☌, a thermometer icon overlay with a half-full bar of red is shown on-screen and the system starts pulling itself back. This internal number is more useful than attaching an external physical temperature measurement because this internal number is what the firmware will use to decide what to do. vcgencmd measure_temp will return a temperature in Celsius. The first useful tool is to measure temperature. Raspberry Pi forum users hypothesize it stands for “VideoCore General Commands” which is good enough for me. Official documentation seems pretty slim, not even an official name. This tool appears to be specific to the Raspberry Pi hardware and wraps a collection of tools to query hardware information. However, it is still possible to detect high temperature condition by using the command line tool vcgencmd. So when a Raspberry Pi is mounted on a robot and not attached to a monitor, we can’t see this icon. A quick search finds that it is put on-screen by firmware and not visible to the operating system. Anyone who has pushed the limits of a Raspberry Pi would have seen a thermometer icon in the upper right corner. While in the process of obtaining proof that a Raspberry Pi 3 is under-powered for certain ROS processing tasks like mapping, I took a little side trip into the world of Raspberry Pi thermal management.
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