2.4 Measure Current Draw of the MSP430 MCU
To measure the current draw of the MSP430FR2476 MCU using a multimeter, use the 3V3 jumper on the J101 jumper isolation block. The current measured includes the target device and any current drawn through the BoosterPack plug-in module headers.
To measure ultra-low power, follow these steps:
- Remove the 3V3 jumper in the J101 isolation block, and attach an ammeter across this jumper. Be sure to use the correct pair of pins as outlined in Section 2.3 to select between eZ-FET power and CR2032 power.
- Consider the effect that the backchannel UART and any circuitry attached to the MSP430FR2476 can have on current draw. Consider disconnecting these at the isolation jumper block, or at least consider their current sinking and sourcing capability in the final measurement.
- If using the CR2032 to supply power, remove all shunt jumpers at J101, except 3V3 in the lower position, and connect J10 with a shunt jumper.
- Make sure there are no floating inputs/outputs (I/Os) on the MSP430FR2476. These cause unnecessary extra current draw. Every I/O should either be driven out or, if it is an input, should be pulled or driven to a high or low level.
- Begin target execution.
- Measure the current. Keep in mind that if the current levels are fluctuating, it may be difficult to get a stable measurement. It is easier to measure quiescent states.
EnergyTrace technology can also be used to compare various current profiles and better optimize your energy performance.