Prior to making any temperature measurements with or without an adapter, the appropriate connections should be made to the NTC from both the BQ21040 and the MCU. The TS pin will connect to one side of the NTC while the other will be grounded as can be seen in the BQ21040 data sheet. Similarly, two GPIO pins from the MCU will be connected to the same side of the NTC as TS. One GPIO pin from the MCU will be used as a current source and the other will be used to monitor the voltage across the NTC. Also ensure that GND from the MCU shares the same GND connection from the BQ21040. A simplified schematic of these connections are shown in Figure 3-1.