3

I want to measure/show the MIPI-DSI 4 lane signals on an oscilloscope. There is MIPI type display has been connected with LVDS-to-MIPI converter. I want to measure the signals at the output side of LVDS-to-MIPI converter, i.e. MIPI signal.

I don't know how can I measure the signals on an oscilloscope. Is there any other special device needed apart from an oscilloscope?

secure
  • 31
  • 3
  • 1
    What property of the signals do you want to measure? – MrGerber Jan 22 '18 at 13:35
  • 1
    MIPI signals are differential which can go into the GHz range. Any idea of your output speed/frequency. MHz or GHz matters greatly! – Oldfart Jan 22 '18 at 13:40
  • @MrGerber Firstly, I just want to check that whether I get MIPI signals or not from LVDS-to-MIPI converter? It is converter IC, so when I send some data(image) to LVDS lane from processor, I should get some signal at the output side of converter. Means on MIPI side. Correct me if I am on wrong path. – secure Jan 23 '18 at 08:51
  • @oldfart It would be around 100 MHz. Also, thanks for pointing this out. I also have to check my LVDS signals frequency. – secure Jan 23 '18 at 08:53

2 Answers2

3

I routinely look at MIPI signals on my scope. Understanding your MIPI signals speed is key to knowing what type of scope you need. For my current application my scope is about 3.5Ghz @ 40Giga-samples per second. I also use a differential scope probe with similar bandwidth. So yes you can look at them on your scope but you need one with appropriate bandwidth and sample rate.

If you just google or go to the sites of some of the majors like Lecroy, HP, or Tek you will see they have whole application suites on their scopes for measuring, characterizing, and even decoding MIPI signals (options of course). You might also consider a serial data analysis package for the scope if you are interested in seeing eyes etc.

You can always rent gear if you don't have one. If it's a home project and you have a 100Mhz scope well...

Some Hardware Guy
  • 15,815
  • 1
  • 31
  • 44
  • Thanks, will keep this in mind. Yes, all majors have specific application suites fro measuring and decoding MIPI signals. I think, with my current oscilloscope, I can not measure it. – secure Jan 23 '18 at 08:57
1

I believe the chips have built in threshold detection using a Resistor tap and propgrammable threshold which triggers an IRQ. So you can sweep the thresholds to determine the level or merely have an min. acceptance criteria.

e.g.

Use Equation 1 to find the trigger voltage for a selected diagnostic slice level.
EL _SLICE_LEV DIAGNOSTIC
R5 R4 R5 V STB_TRIGGER
where: V STB_TRIGGER is the minimum voltage required at the input connector to trigger the STB interrupt on the ADV7281/ADV7281-M/ADV7282/ADV7282-M. DIAGNOSTIC_SLICE_LEVEL is the programmable reference voltage.

Tony Stewart EE75
  • 1
  • 3
  • 54
  • 182