Low-Cost USB signal measurement frontend.
USB View is a low-cost USB signal measurement frontend that allows users to visualize and analyze USB signals in real-time. It is designed to be easy to use and affordable, making it accessible for hobbyists, students, and professionals alike.
USB signal measurement is challenging due to at high frequency, input capacitance of normal oscilloscopes probes in the range of tenths picofarads can significantly distort the signal and cause the device under test to malfunction. USB View addresses this issue by using TI BUF802, a 3GHz high-speed buffer with only 2.4pF input capacitance, ensuring accurate signal representation without loading the USB lines.
Gerber files and BOM are available in the Production folder for manufacturing.
Impedance control is tuned for JLCPCB 7628 stackup. JLCPCB Part column in BOM allows to populate the SMT order automatically without manual part selection, some non-critical parts are sourced from JLCPCB economical catalog instead of Part Number for cost reduction.
Potentiometer R23_DP and R24_DN controls the DC gain, rule-of-thumb setting is having 2.1kOhm between pin 1 and GND. Usually fine-tune is not necessary, if needed, apply a rectangular wave on the data lines then adjust the same way as oscilloscope probe compensation.
I'm using a Siglent SDS2504X plus oscilloscope with 500MHz bandwidth and 2GSps sampling rate which is short of the ideal 1GHz bandwidth and 4GSps sampling rate for USB2.0 high-speed signal measurement, but still works fine for most cases.
Continuous 40bits string without transition, the voltage level at the end is used by high-speed disconnection detector.
Transmit waveform measured at device side (Template 3 cp 7.1.2.2).
With manually applied mask.
[1] 2 GHz Active Probe https://jmw.name/projects/active-probe/
[2] USB 2.0 Specification https://www.usb.org/document-library/usb-20-specification
[3] TI BUF802 https://www.ti.com/product/BUF802
[4] ThunderScope https://github.com/EEVengers/ThunderScope
This project is licensed under the MIT License - see the LICENSE file for details.