• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 33 subscribers
  • Views 292 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

DS90UB940-Q1: No signal output when paired with UB947 or UB927

DS90UB927Q-Q1: Deserializer output to RGB888 parallel or MIPI CSI with GPIO[1:0] as interrupt input

Wei Xiao
Intellectual 595 points
Part Number: DS90UB927Q-Q1
Other Parts Discussed in Thread: DS90CR288A, DS90CF386

Tool/software:

We have current design working with UB928 as deserializer and its GPIO[1:0] as button and touch interrupt inputs. However, in our new design, the downstream IC only support RGB888 parallel or MIPI CSI input. With no option to set UB927 to 18-bit mode, that rules out UB926.

Now we need suggestion on IC or IC combinations. What we have considered so far are as follows. 

Either we can keep UB928 and add an IC converting LVDS to RGB888 parallel. That should keep the I2C programming unchanged. However, we need recommendation on which IC from TI catalog is a better fit to convert UB928 output to RGB888 parallel. The application now needs support on both 800x480 and 1280x768 pixels active display area with 60 fps. preferably, it should also support at least 1080p 60fps image signals.

Or, we can use UB940 to output MIPI CSI to downstream IC. Looking at the datasheet, it seems that current I2C programming for UB928 should work for UB940. Please advise if there are any caveats using UB940 to replace UB928.

  • 0
    TI__Mastermind 36875 points

    Hello,

    The UB926 can support both 18-bit mode and 24-bit mode as well as the UB927. If the OLDI output is set to 18-bit mode, the third data lane will not be active but as long as the VS, HS, DE, and PCLK are transmitted to the UB927 the signal can be recovered at the deserializer.

    The UB940 and UB928 feature similar registers for general configuration and GPIO. The main difference is that if a non-standard resolution is used it will require additional programming of CSI registers in the UB940. There is an app note that covers this programming. I will link it below.

    https://www.ti.com/lit/an/snla303/snla303.pdf?ts=1757974274523&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FDS90UB940-Q1

    If you are needing a system to transmit video up to 1080p 60fps, then the UB92x devices will not support this resolution. A system with a UB947 serializer and a UB940 deserializer can support 1080p 60fps video.

    Best,

    Jack

  • 0 in reply to Jack Scherlag
    Intellectual 595 points

    Hi Jack,

    Thank you for the insights. UB927 is an OEM part and we have no control over it to set to 18-bit mode.

    Please help address the other question. If we are going to use UB928 and and IC to convert Open LDI to RGB888 parallel, what IC would you recommend? DS90CF386 and DS90CR288A seem to cover the PCLK range I mentioned. Do you have better option to recommend?

  • 0 in reply to Wei Xiao
    TI__Mastermind 36875 points

    Hi Wei Xiao,

    The DS90CF386 and DS90CR288A are the relevant options for converting LVDS to RGB888 parallel. The main difference between these devices is that the DS90CF386 strobes the data on the falling edge. The DS90CR288A strobes the data on the rising edge.

    The below image comes from the DS90CF386 datasheet. I added the red lines on the image to visually show how the data is strobed on the falling edge of the clock. For the DS90CR288A it will be the rising edge instead. The TCON will say which options it can support.

    DS90CF386 falling edge strobe

    Best,

    Jack