Signal being suppressed

[parkinsonp]

I have the hispeed logic prob connected to the output of a Silicon Labs CP2108 USB-UART. The UART is connected to a Single Wire Interface so the TX and RX are connected together. The circuit transmits and receives until the logic prob is connected. When the probe is connected the TX signal is transmitted but as soon as the end point switches to to RX mode the circuit stops transmitting. Remove the probe and the circuit works fine. 

Any ideas? 

[attila]

Hi @parkinsonp

Make sure to have ground connection between the devices.
The DIN lines have lower impedance that may interfere with the driver circuit. Try using the DIO lines.
https://reference.digilentinc.com/reference/instrumentation/digital-discovery/reference-manual#input_dividers
https://reference.digilentinc.com/reference/instrumentation/digital-discovery/reference-manual#io_level_translators

[parkinsonp]

I have tried the DIO24 port. I have tried the low speed inputs for DIN. None of these things work. I am trying to monitor a 3.3V serial channel. Logic high is 0.7V. I have used a 3mA drive port and a 12mA drive port. Grounds are connected. Nothing is having an impact on the Digital Discovery from suppressing the signal. 

[parkinsonp]

I did find a working combination. DIN with no high speed adapter and the high drive 12mA port. I need to write a custom protocol for the protocol analyzer. I am monitoring a single wire Microchip protocol that is unique to them. Is there any examples of a custom protocol analyzer. 

 

[attila]

Hi @parkinsonp

See the Example menu: