Compiler/DLP4500: Mirror refreshing disabled in Pattern Sequence Mode

Hi Hirak,

We also reproduced the behaviour using the API.
The code below shows step by step what we previously did in the GUI interface.
After switching from video mode to pattern sequence mode the DMD is still active.
Just for reference: we are using DLPC350 with DLP4500 (there are no LEDs, just the DMD) and version 3.1.0 of the GUI interface/API.

#include "pch.h"
#include <chrono>
#include <thread>
#include <iostream>

int main(int argc, char *argv[]) {

	unsigned int imageIndex = 0; // test pattern

	// connect to DLPC
	DLPC350_USB_Init();
	DLPC350_USB_Open();
	if (!DLPC350_USB_IsConnected()) {
		return -1;
	}

	DLPC350_SetPowerMode(false); // turn on normal mode

	DLPC350_SetMode(false); // go to video mode
	DLPC350_LoadImageIndex(imageIndex); // load image from flash memory

	std::this_thread::sleep_for(std::chrono::seconds(3)); // here we see refreshing

	DLPC350_SetMode(true); // switch to pattern sequence mode

	std::this_thread::sleep_for(std::chrono::seconds(3)); // here we don't see refreshing, but the image is still displayed

	DLPC350_SetPowerMode(true); // go to standby mode
}

Best regards,

Robert

Cool! This is actually what we are looking for!

We want to disable the refreshing during a small time range (~ seconds), to be able to perform our experiment.

However, we also want to use an external trigger to display the pattern, which is only possible in pattern sequence mode.

So you are saying the state of the sequencer is controlling the mirror refreshing? (What exactly is the sequencer?)

Can we perhaps (using the API) put the sequencer to idle mode or influence the refreshing in some other way, while using pattern display mode? (see also this question: https://e2e.ti.com/support/dlp/f/94/t/726387)

Best regards,

Robert

Hi Hirak,

we tried this and successfully controlled a pattern sequence on the DMD via TRIG_IN1.

However, on the one hand the refreshing still occured and on the other hand the trigger behaviour was different than described by the guide book: For every rising edge the next pattern was displayed until the next falling edge. According to the guide, the next pattern should be shown when detecting a rising edge and be displayed until the next rising edge.

Both issues can be seen in the following image (top: intensity of the DMD, bottom: trigger signal):

Kind regards,

Robert

Hi Hirak,

Unfortunately, we couldn't get a pattern to stay on the DMD after the negative edge.

Using the GUI we put only one pattern in the "sequence", Clear DMD unchecked, repeat, trigger mode "internal/external", pattern source "flash".

We tried different trigger settings and also changed the pattern exposure and pattern period (always the same value for both).

When noticed, that the pattern only displayed when adding it with the "internal trigger" setting.

But the pattern still displays according to the external trigger (displayed between rising and falling edge) independent of what pattern exposure/period we choose.

The settings "external positive/negative" result in the pattern not being displayed although the external trigger is connected.

Also we found that the refreshing period depends on the pattern exposure time.

However, the upper limit seems to be 500µs.

Can you reproduce this behaviour?

Regards,

Robert

Hi Hirak,

thanks a lot.

We reproduced what you describe by switching to the other TRIG_IN.

As you can see below, we have 4 pins of the J7 connector connected (blue cables = signal, black cables = ground).

However, we don't know which of the blue ones is G19=TRIG_IN1 and which is F22=TRIG_IN2.

It seems, that we now connected TRIG_IN1 correctly.

But there is one thing we couldn't reproduce: When adding more than 2 patterns to the sequence, the third pulse will not change to the third pattern, but again to the first one thus alternating between just two patterns.

When adding the "Clear DMD" option to at least one pattern, more than 2 patterns can be displayed, however, with refreshing and not in a linear way, but alternating in a strange way between one of the patterns and the rest.

Regards,

Robert

Thanks Hirak.

We tried flashing an older firmware to see if that would resolve the bug.

However, during the upload the program froze and left behind a corrupted flash image.

To recover we would have to use the JTAG tool, right?

In that case, what is the connector for the JTAG cable on our model of the LightCrafter?

Your schematic says it is J25 for the other model.

Regarding the image loading times it would probably be more efficient to show multiple patterns from just one flash image.

Can this be done using different bitplanes of one image for each pattern?

Regards,

Robert