Support Question of the Week: Translate Signal Levels for an Embedded I2C Device and a Beagle Protocol Analyzer

Q: I'm using the Beagle I2C/SPI Protocol Analyzer to analyze the bus traffic of an embedded I2C device that runs on 1.2V. It looks like I can use the Level Shifter Board - do I need to power the target I2C with the Beagle analyzer or can I use an external 1.2V power supply?  Also, do I need to add pull-up resistors for the Beagle I2C/SPI Protocol Analyzer as well as the target device?

Thanks for your questions! The Beagle I2C/SPI Protocol Analyzer provides built-in resistors, and you have the option to power the target device with the Beagle analyzer's power source or an external source. The Level Shifter board can be configured to translate signal levels for 1.2V, 1.5V, 2.5V, 3.0V and 3.3V devices.

Use the Level Shifter Board to Translate Signal Levels between an Embedded I2C Device and a Beagle Protocol Analyzer Figure 1: Level Shifter Board

To interface with an I2C device that runs on 1.2V, ensure the analyzer side is powered with 5V and the target side of the board is powered at 1.2V.

Providing 5V to the Level Shifter Board:

  • The Beagle I2C/SPI Protocol Analyzer can provide 5V directly to the Level Shifter Board through the ANALYZER Socket.

Configuring 1.2V signal levels and selecting the target power source:

  1. Connect a jumper across the 1.2V pins. This translates the signal level to 1.2V. It also shifts the supply voltage provided by the Beagle I2C/SPI Protocol Analyzer to 1.2V.
  2. Powering the target device:
    • To use the Beagle analyzer voltage output to power the target I2C device, connect a jumper across the TPWR pins .
    • To use an external power source instead of the Beagle analyzer, remove the jumper from TPWR jumper, and connect the external 1.2V power source to the TPWR pin on the EXT TGT header.
  3. To confirm the configuration, verify that both the POWER and TARGET LEDs are turned on the Level Shifter Board.

The Level Shifter Board does not provide pull-up resistors for either side. However, pull-up resistors can be provided by the Protocol Analyzer as well as the target board.

Pull-ups for the Beagle Protocol Analyzer:

  • You can use the internal pull-ups of the Beagle I2C/SPI Protocol Analyzer. For each I2C line that is used as a digital input line (GPIO) to the Adapter/Analyzer side, a pull-up resistor is required on the Adapter/Analyzer side.

Pull-ups for the target I2C device:

  • For the target device, we assume pull-up resistors are provided on the target board. The devices may communicate without the pull-ups, but for optimum performance, pull-ups should be used to ensure the signals of the target device operate at the correct voltage levels.

For more information about the Level Shifter Board, Beagle Protocol Analyzers and other Total Phase products, please refer to the following:

Level Shifter Board
Level Shifter User Manual
Beagle I2C/SPI Protocol Analyzer
Beagle Protocol Analyzer User Manual
Total Phase Products
Product Selector Guide

We hope this answers your questions. If you have other questions about our host adapters, API and software tools or other Total Phase products, feel free to email us at sales@totalphase.com  or support@totalphase.com.

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