About Logic Pro hardware

Support
1

Hello!

I’m trying to use a plain parallel bus. The reason is that BiSS is usually differential,
and I was using 2 channels only, MA+ and SLO+. But I need to get differential signals,
so I was planning to set ch0 as MA+, ch1 as MA-, CH2 as slo+ ch3 as SLO-.
→ The scope keeps reporting an error. Then I discarded the BiSS setting and used
the parallel bus. Unable to set it. Is there anything to install in order to use the parallel bus?
In the meantime I have setup 4 analog channels.

I was also wondering: the logic pro inputs are single ended, right?
I’m asking that because I need to check a BiSS connection which is differntial.
In case of differential, the negative wires would also be numbered, I think.
Is there a way to process differential signals (for example if I used ch0 as MA+,
ch1 as MA-, CH2 as slo+ ch3 as SLO-, it might work).

Next, About the trigger:
If I choose 3.3V, does it mean that the trigger is 3.3V or that the signal max value is
3.3V like in most of the CPUs these days?

Thanks for any hint.

Elodie.

2

See: Decode Differential and High Voltage Data | Saleae Support

See Voltage threshold description: Supported Voltages | Saleae Support

TL;DR:

Saleae Logic probes are all single ended, and all ground wires are connected to each other and to USB ground, so cannot be used as independent low/negative reference on balanced/differential signals. If the differential signal(s) reliably cross the (fixed or selectable) digital voltage threshold as per above link, for pro devices:

  • 1.2V Voltage Option
    • Voltage threshold: 0.6V
  • 1.8V Voltage Option
    • Voltage threshold: 0.9V
  • +3.3V Voltage Option
    • Voltage threshold: 1.65V
    • Use this option for all IO standards 3.3 volts or above.

… and signal stays within hardware limits:

  • Over-voltage protection provides safety to +/- 25V

… then just probe one end of the differential signal to decode. As per other link, this should work for RS422 levels, but depends on your hardware’s line drivers.