DLP EVM selection for specific application

Hi Vincent,

Thanks for your question. Sorry about the confusion surrounding the capabilities of the EVM, I'll take a note to clarify the language in the user's guide.

In your application, are you streaming patterns in through the video port of the Lightcrafter? Or are you pre-storing patterns in flash memory? If you can let me know a little more about your application, that would be helpful. If pattern sequence modes aren't crucial, then perhaps a regular display EVM would be a better choice.

-Paul

Hi Paul,

Thanks for the prompt answer!

We need to have continuous stream patterns through video port , flash is not an option at given fps, I guess. And if I am not mistaken the flash response time does not allow high fps. Due to flash image loading time, which is at least applicable in dlp4500 frambuffer configuration:
e2e.ti.com/.../375969


We need to stream pattern sequence at the highest bandwidth that is allowed by typical interface ( say HDMI 2.0) at 24bit and 120 -140 Hz. Resolution-wise, the highest resolution possible at given bandwith/dmd screen pixel size will be great. But full HD will do too.
Sorry for not getting more specific about our application. Yes indeed, we have to have the pattern sequence mode. We need real time control on pixel-bit level to be able to synchronize with other parts of our optical system.

Thank you!

Vincent

Vincent,

Thanks for the additional information. How many patterns do you think you'll need? If it's less than 48 and they can be repeated, then the Lightcrafter 4500 might still be okay because the flash frame rates are quite high in that scenario, especially for lower bit depth patterns.

The other important question is whether or not your application requires the full 24 bits. Are your frames made of 3 8bit patterns (one for each color channel) that you would like displayed at 120Hz? Or are you packing binary patterns into a 24 bit frame?

-Paul

Hi Paul,

We need continuous stream of frames. Definitely more than what flash memory offers and none repeating.

And yes we need full 24 bits. We need to pack information for structured light pattern equivalent to 24 bits(per frame) at 120 Frames per second. It could be 8 bit patterns and 3 times faster too... If this, for any reason, is only way to go. I hope this helps.

Thanks!

Vincent

Hi Vincent,

If the patterns you are interested in projecting are 1bit patterns, you can use the Lightcrafter 4500 to accomplish what you are looking for with external video streaming. Take a look at table 2-47 in this document: www.ti.com/.../dlpu010f.pdf

Basically, you would pack your 1 bit patterns into a 24 bit frame and then display each binary bit plane with a period of 347us, which is supported by the Lightcrafter 4500. Does that solve your problem?

-Paul

Hi Paul,

Thanks for the hint.
Just to make sure I understood right. Here is little snap of C code using dlp350 API. Only the part of sequence loading... Does this describe what you proposed?


--------------
/*** API calls to initiate pattern sequence mode etc...


DLPC350_SetPatternDisplayMode(1)

DLPC350_SetExposure_FramePeriod(347,347)

DLPC350_SetPatternTriggerMode(0)

DLPC350_AddToPatLut(1,0,1,2,0,1,0,0)<0;

for(int i=1; i<24; i++) {DLPC350_AddToPatLut(3,i,1,2,0,1,0,0)<0}


/***and other API calls to send, Run and Validate sequence

-------------------------


So if we properly trigger and hdmi is locked at 120 HZ@24bit, the above sequence should be able to run binary bit plane at 2880 Hz. The binary planes will be loaded from 24bit frame which itself is running at 120HZ.

Thanks!

Vincent

Hi Vincent,

Your understanding is correct. I would try this approach with the GUI first so that you can validate that the concept makes sense before moving the code - that way you know it isn't the custom code which is causing issues.

-Paul

Paul, I really appreciate the help. So far the code above does not work at 120 Hz. But there might be other reasons for that.

Vincent

Hi Vincent,

At 120Hz, there are a couple nuances that need to be consider as far as input video blanking times. Try slightly lower like 115Hz or 118Hz and see if that works. You can find the details for 120Hz here: https://e2e.ti.com/support/dlp__mems_micro-electro-mechanical_systems/advanced_light_control/w/dlp_faq/3435.how-do-i-display-video-at-120hz

Hope that helps,

Paul

Dear Paul,

Just a brief question. Still trying to figure out  how to get higher frequencies than 60 Hz. I have almost always got "buffer freeze" and the software reset not always work to get beck to normal operation. I was wondering is this safe? The DMD could not get damage doing this. The buffer freeze is always accompanied with DMD getting stuck in weird positions.  

Thanks

Vincent