NXP Application Code Hub

NXP KM metrology

NXP KM metrology software has two use cases:

• it calculates the charging parameters (current, voltage and power) of an electric vehicle (EV) by using current and voltage samples stored in memory
• it serves as an Analog Front End (AFE) sending data over SPI

In both cases, current values are adjusted by rotating the potentiometer.

Boards: TWR-KM35Z75M

Categories: Analog Front End, Industrial

Peripherals: DISPLAY, I2C, ADC, SPI, UART

Toolchains: MCUXpresso IDE

Table of Contents

1. Software
2. Hardware
3. Setup
4. Results
5. Support
6. Release Notes

1. Software

• MCUXpresso IDE v11.9.1 or later
• SDK_2_15_000_TWR-KM35Z75M for TWR-KM35Z75M

2. Hardware

Mandatory hardware:

• TWR-KM35Z75M board
• a board with exposed UART and SPI interfaces

Note: EVSE-SIG-BRD1X/2X is used in this document to exemplify hardware connections. If you are using another board, check the documentation and schematic to adapt the wiring.

3. Setup

3.1 Hardware assembly

To use TWR-KM35 for its metrology capabilities, you need only a UART connection between the TWR-KM35 and the EVSE-SIG-BRD1X/EVSE-SIG-BRD2X (or any other board), as illustrated in the following image.

To use TWR-KM35 board as an AFE, you must use SPI interface. The UART connection is optional. The connections between the TWR-KM35 and the EVSE-SIG-BRD2X (or any other board) are illustrated in the following image.

Connect a microUSB cable between you personal computer and J27 connector on TWR-KM35 to power on the board.

To power on the EVSE-SIG-BRD1X/EVSE-SIG-BRD2X, place J2 on position 1-2 and connect a 5V power supply to J1 barrel connector. If you are not using EVSE-SIG-BRD1X/EVSE-SIG-BRD2X, check the schematic of the corresponding board for powering options.

3.2 Software setup and flashing

1. Clone the APP-CODE-HUB/dm-nxp-km-metrology
2. Import the project from filesystem or archive

3. After importing the project, click on it in the workspace to select it, then click on the hammer button to build it
4. To flash the project, go to Quickstart Panel and select Debug with LinkServer probes. When the debugger gets to main() function, click on Resume All Debug sessions to start the program

4. Results

Once the hardware connections are made and the TWR-KM35 is flashed, the current value is displayed on the board's display and metrology data is sent over UART.

To change the current value, rotate R21 potentiometer (upper right corner, on the back of the board).

5. Support

Questions regarding the content/correctness of this example can be entered as Issues within this GitHub repository.

Warning: For more general technical questions regarding NXP Microcontrollers and the difference in expected functionality, enter your questions on the NXP Community Forum

Project Metadata

6. Release Notes

Version	Description / Update	Date
1.2.0	Initial release on Application Code Hub	April 11th 2025

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