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4.8 Ultra-Lower-Power Coprocessor 4 PERIPHERAL INTERFACE
4.6 Temperature Sensor
The temperature sensor generates a voltage that varies with temperature. The voltage is internally converted via
an analog-to-digital converter into a digital code.
The temperature sensor has a range of -40°C to 125°C. As the offset of the temperature sensor varies from
chip to chip due to process variation, together with the heat generated by the Wi-Fi circuitry itself (which affects
measurements), the internal temperature sensor is only suitable for applications that detect temperature changes
instead of absolute temperatures and for calibration purposes as well.
However, if the user calibrates the temperature sensor and uses the device in a minimally powered-on application,
the results could be accurate enough.
4.7 Touch Sensor
ESP32 offers 10 capacitive sensing GPIOs which detect capacitive variations introduced by the GPIO’s direct con-
tact or close proximity with a finger or other objects. The low noise nature of the design and high sensitivity of the
circuit allow relatively small pads to be used. Arrays of pads can also be used so that a larger area or more points
can be detected. The 10 capacitive sensing GPIOs are listed in Table 6.
Table 6: Capacitive Sensing GPIOs Available on ESP32
Capacitive sensing signal name Pin name
T0 GPIO4
T1 GPIO0
T2 GPIO2
T3 MTDO
T4 MTCK
T5 MTD1
T6 MTMS
T7 GPIO27
T8 32K_XN
T9 32K_XP
Note:
For more information about the touch sensor design and layout, refer to Appendix A Touch Sensor.
4.8 Ultra-Lower-Power Coprocessor
The ULP processor and RTC memory remains powered on during the Deep-sleep mode. Hence, the developer
can store a program for the ULP processor in the RTC memory to access the peripheral devices, internal timers
and internal sensors during the Deep-sleep mode. This is useful for designing applications where the CPU needs
to be woken up by an external event, or timer, or a combination of these events, while maintaining minimal power
consumption.
Espressif Systems 22 http://www.espressif.com