Even the STM32 built-in temperature sensor has really poor accuracy, like +- 5°C. Adding NTC resistor to ADC pin costs 2 cents and gets you to +-1°C or better.

For Celsius degrees the output voltage of IC2 is set with P1 at 2.73 V when the temperature of IC1 is 0°C. The calibration of the temperature indicator at 100°C is done by comparing it with a ...

Although this circuit connects the DS18S20 1-Wire temperature sensor to a Cypress CY8C26443 PSoC microcontroller, designers can easily adapt it to connect other 1-Wire devices to any microprocessor.