4.2.5 Temperature Sensor
ATmega256RFR2 Xplained Pro features an Atmel AT30TSE758 temperature sensor chip with an 8kbit serial EEPROM inside. The sensor includes programmable high and low temperature alarms, user-selectable temperature resolution up to 12 bits, and an I2C/SMBus™ compatible serial interface.
| AT30TSE758 temperature sensor pin | Pin name | Pin on ATmega256RFR2 | Comment |
|---|---|---|---|
| 1 | SDA | PD1 | Data line of serial interface |
| 2 | SCL | PD0 | Clock line of serial interface |
| 3 | ALERT | NC(1) | Temperature alarm signaling pin |
| 4 | GND | GND | |
| 5 | A2 | - | Address line for serial interface, by default pulled low |
| 6 | A1 | - | Address line for serial interface, by default pulled high |
| 7 | A0 | - | Address line for serial interface, by default pulled high |
| 8 | VCC | VCC |
- Alert pin is available on a test point hole close to the sensor.
The temperature sensor has two TWI addresses, one for the temperature sensor and one for the EEPROM. The addresses are "0b1001 A2 A1 A0" for the temperature sensor and "0b1010 A2 A1 A0" for the EEPROM. The address selection lines (A2, A1 and A0) of the temperature sensor chip is by default pulled high for A0 and A1, and low for A2, through 100kΩ resistors, which makes the default addresses 0b1001011 and 0b1010011. Soldering the straps on the front of the ATmega256RFR2 Xplained Pro board for An will alter that bit in the address to low or high. Each strap is marked in silkscreen with A0, A1, and A2 as shown in Figure 4-1. When communicating with the EEPROM, part of the TWI address is used as a page address, for more details see the device datasheet.
