Device Sensors

The ECM1900 has 4 LTC2991 device sensors onboard that reports various voltage, current, and temperature readings. These sensors communicate through an I2C line connected to the processing system (PS) on the ZYNQ MPSoC. The I2C line is connected to MIO pins 16-17 on the PS and can be controlled from the provided Linux image. It can be accessed using the I2C device file “/dev/i2c-0”. Example usage is provided in the device-sensors.py file installed in the tools directory of the image.

You’ll need to read the LTC2991’s datasheet to learn more about the device. A brief description of the important information you’ll find within the datasheet is provided below:

• Information about the V1-8 pin’s operating modes: voltage, current, and temperature.
• Configuration registers to setup the modes for the V1-8 pins.
• Register map to retrieve the sensor readings.
• Conversion equations to perform on the RAW sensor readings.

Below are how the 4 LTC2991 device sensors are connected onboard the ECM1900. Please note that the Rsense resistor we use between the Current Diff Pairs is 0.005 ohm. You can read about the Rsense resistor’s current calculations in the LTC2991’s datasheet.