Energy Probe requirements

The Energy Probe has the following requirements:

• An installation of ARM DS-5 Basic or Professional Edition, version 5.9 or later.

• A Streamline-enabled target. For Linux and Android targets, this requires the gator driver and daemon to be installed on the target.

• An Energy Probe Unit.

• A USB extension cable.

• USB drivers for the Energy Probe.

• A target that has 2-pin IDC 0.1" power measurement headers. The target also requires a shunt resistor with a supply voltage less than 15V and rated at least 0.5W. The shunt resistor needs a 1-pin IDC ground terminal and must not drop more than 165mV.

Precautions

The Energy Probe has flying leads and must be carefully connected to your target. Do not plug the green ground wire into anything but the target ground. This includes I/O pins and power pins. Doing so could cause damage to your Energy Probe or the power supply of your target.

Determining the optimal shunt resistor value

With 20x amplification, Energy Probe requires correct selection of a shunt resistor to provide the best possible dynamic range in power measurement, while avoiding saturation of the input of Energy Probe. A shunt resistor with a value too low reduces measurement dynamic range, resulting in less resolution in the power data. A shunt resistor with a value too high can cause the input stage of the Energy Probe to saturate, which causes a flat line in the charts related to Energy Probe in the Streamline Timeline view.

To avoid input saturation, the drop across the Rshunt resistor must never be more than 165mV. You can also use the following equation to determine if your shunt resistor is appropriate:

``` 	RShunt(max) = 165 x Vsupply / ( 1000 x Power )
```

`Vsupply` is the input/core voltage. `Power(max)` is the maximum power that the Energy Probe measures. `Rshunt(max)` is the maximum value of the shunt resistor. A shunt resistor value greater than `Rshunt(max)` might cause input saturation.

This equation provides the absolute maximum value for Rshunt. Use a value that is more than five percent lower than this value to allow for component tolerances.

Examples

• 5V power supply, 8W(max), Rshunt(max) = 100mOhm

• 1V core voltage, 2.5W(max), Rshunt(max) = 50mOhm

• 1.5V core voltage, 0.4W(max), Rshunt(max) = 500mOhm.

Notes

When connecting the Energy Probe, consider the following:

• The black and white probe closest to the green wire is Channel 0.

• For best results, attach Channel 0 to the power source which best represents the CPU load. Streamline aligns the power data with the software activity by maximizing the correlation of Channel 0 with the CPU load.

• The probe white wire is V+. The black wire is V-.