How Do I Safely Capture USB Data Between an iPhone and a Charger?
2024-09-18
Rena Ayeras

Image by NoPixelZone

Question from the Customer:

I will be using the Beagle USB 480 Protocol Analyzer to capture data between an iPhone and a new charger design. I understand there may be power limitations – what is the safest way to connect the Beagle USB 480 analyzer in this setup?

Response from Technical Support:

Thank you for your question! There are power constraints to consider, and we have an example of a similar setup that may be helpful for you.

Capture Data within Power Constraints

It is important to verify that the output power of the charger does not exceed the power specification of the Beagle USB 480 analyzer:

  • The inputs are rated for 1A continuous current and 0 to 24V.

  • The VBUS current/voltage measurement is sampled every 12 x 2^16 clock cycles, which is approximately every 13.1 ms.

  • The maximum current/voltage measurement error is ±50 mV and ±5 mA at 5 V and for current up to 500 mA.

Note - When using the Beagle USB 480 Power Protocol Analyzer above the rated current and voltage, extreme caution is advised. Customers who choose to do so are at their own risk and may cause permanent damage to the analyzer. Applying current and voltage in excess of the warranted operating range may damage the Beagle analyzer.

VBUS Considerations

To recognize that a host is present, the Beagle USB 480 analyzer must detect 5V on VBUS . If the target system does not provide 5V, which seems likely for your setup, you can override VBUS, which can done by executing a Data Center Software command with the Command  Line as shown below:

Data Center Software command to override VBUS requirement

The same task can be accomplished with Beagle Software API. For information, please refer to API Documentation in the Beagle Protocol Analyzer User Manual.

Example Setup for Capturing Data

Assuming the voltage and current of your charger device is within specifications, the example setup we have is very similar to the diagram that you showed us. The photograph shows an Android-powered phone in USB accessory mode and a USB Flash stick as a test device.

We hope this answers your question. Additional resources that you may find helpful include the following:

If you want more information, feel free to contact us with your questions, or request a demo that applies to your application.