Tea is ready

A DS18B20 temperature probe sits in a mug of tea (data on GPIO4, 3.3 V, with a 4.7 kΩ pull-up — or buy the probe module that has it). A green LED on GPIO17 lights when the tea has cooled below 60 °C and stays dark while it is hotter.

The probe appears as /sys/bus/w1/devices/28-*/w1_slave; the line ending in t=58250 means 58.25 °C, and each reading takes about 0.75 s.

The test tea is 85 °C, 70 °C at 2 s, and 55 °C at 4 s.