Meat thermometer

A probe in the roast: a DS18B20 (data GPIO4, 3.3 V, 4.7 kΩ pull-up), a 16×2 LCD (I²C 0x27), an active buzzer on GPIO25 (may draw up to 25 mA) and a silence button on GPIO27.

• Line 1 always shows the temperature: Meat: 50.0C.
• At 70 °C or more, line 2 shows READY and the buzzer sounds; below 70 °C line 2 is blank and the buzzer is quiet.
• The silence button stops the buzzer (the LCD still says READY).

A probe reading takes about 0.75 s. The test roast is 20 °C, 50 °C at 2 s, 72 °C at 4 s; the button is pressed at 7 s.