Unstable Video Output when using 24bit RGB video input.

Hello Glen,

DLPC350 provides useful information about input video signal detection status. Refer to DLPC350 Programmer's Guide version 'E',

Section 2.1.5.

There is another discussion thread on the same topic https://e2e.ti.com/support/dlp__mems_micro-electro-mechanical_systems/f/924/p/388939/1375812

Regards,

Sanjeev

Hi Sanjeev,

Thank you very much for replying to my email. We checked the values of register 0x01 and all of the timing, video resolution, number of lines, etc are perfect. Exactly what we would expect. FYI, our video input via the RGB port is 800x600 @60Hz.  This problem occurs only when external video is being used with the RGB port. We do not see the issue with the TI logo or any of the internal test images. 

In addition, the problem is also there whether we use 1 LED (any color) or all at the same time. We even tried to freeze the video this helped, but not 100%.

Any additional thoughts on what we could be doing wrong?

Glen

Hello Glen,

To simplify the issue you are facing, can you configure the video output to 912x1140 @ 60Hz or 1280x800 @ 60Hz. 

Can you also readout the values of 0x01 Register?

Especially the BYTE#0 should be stable and value be set to 0x02 Detected.

if DLPC350 is getting in loop for redecting the source then there is problem with the source side.

Regards,

Sanjeev

Hi Sanjeev,

We spent the last few days verifying the integrity of the  incoming video signal to the DLPC350, and we found that the input video is 100% stable. Byte 1 from Register 0x01 is always 0x02. As you know, this value means that the DLPC350 is seeing a stable video on its RGB port. We do notice however, that the PWM signal is NOT stable and that would could the problem that we are seeing. However as I mentioned before this only occurs during input video mode.

Any thoughts?

Glen

Hello Glen,

Let me know exactly which PWM are you talking about? Are you referring to any specific signal coming out of DLPC350,if so provide the details about the same.

Also, please confirm that you are using this device in Video Mode, not in Pattern Mode with source as RGB video port.

Does your board has USB interface? if so then use our GUI and read the all the parameters under Video Mode tab, attach the GUI snapshot.

Regards,
Sanjeev

Hi Sanjeev,

When we measure across the PWM for the Green LED, for example, while the TI Logo is being displayed at power up, the PWM signal is stable. Shortly after the TI Logo is displayed, we can see the boot logo of our OMAP board which is feeding 24bit RGB into the port  When we probe the same point (The Green PWM signal from the DLPC350)  we can see that the signal is unstable. From our standpoint the video is blinking/shaking. However, the varying duty cycle that we see on the PWM signal from the DLPC350 seems top correlate the "blinking/shaking" video.

Please note, that the unstable PWM signal that we measure is obserable also on the RED and BLUE PWM signals from the DLPC350.

We are not writing any I2C commands that would cause the DLPC350 to go into Pattern. By default, it boots into Video Mode- Reg 0x69 bit 0 = 0.

The USB interface is connected to our HOST so its not possible to run the GUI application while of our board is connected. However, if you can tell me what registers the GUI application is reading (with respect to the paramters under the Video Mode tab) then I can read them manually via I2C and send you the results.

Glen

Please send following register values -

HW Status - 0x20
System Status - 0x021
Main Status - 0x22
Video Signal Status - 0x01 - Monitor this signal over time, as especially check if the BYTE#0 Signal Detection Status going through repeated lose lock and re-lock.

Regards,
Sanjeev