Hi,
I have a Pico DLP v2 with a Beaglebooard. I'm booting into Angstrom 2.6.32 off of an SD card. I have a couple of questions:
1. I intend to develop structured light applications. Currently, I'm trying to get the internal patterns example in dlpa021.pdf running. I've entered the commands for the internal example for 1200HZ and end up with a flickering purple screen with vertical black stripes. I must admit, I'm a little confused about the syntax for the I2C command for choosing a pattern.
According to dlpa021.pdf "I2C sub-address xD7, data x00000000 (pointers x01, x00)" sets the first two patterns, and "I2C sub-address xD8, data x00000021 (pointers x03, x02)" sets the 3rd and 4th patterns. I've entered these with i2c-tools as:
2. I am powering the beagleboard through with a USB cable via the USB OTG port. I had a kernel panic error, so I used the Angstrom uImage with lower power consumption. It boots, but results in period random ASCII characters on the serial port. I have since powered through a Y-cable with the normal Angstrom uImage, but still get the kernel panic error. I'm considering buying a 5V power supply, but it was previously reported [1] that I2C commands do not work with the power supply. Any other suggestions for being able to use a 'normal' Angstrom uImage and I2C commands?
Thanks for any comments and suggestions!
[1] http://e2e.ti.com/support/dlp__mems_micro-electro-mechanical_systems/f/94/p/62015/280976.aspx
[2] dlpu002a.pdf
Tommy,
I can see your pictures, and understand your question. Unfortunately, the Pico Kit v2 does not provide a means for doing what you are asking while in the internal structured light mode. In the internal structured light mode, there are a number of internally stored patterns )and their inverses) which can be selected for a sequence of repeating patterns. There is no provision for user defined patterns, such as you show.
It would be possible for you to define such patterns in the external 1-bit (1440 Hz) mode. In the external mode the pattern must be supplied in continuous real-time to the Pico via the HDMI video port formatted as a 60 Hz 24-bit RGB video frame.
If you have not already done so, please refer to the Application Report Using the DLP Pico 2.0 Kit for Structured Light Applications (Rev. A) (dlpa021a.PDF) available from
http://www.ti.com/litv/pdf/dlpa021a
The description and details of the internal and external structured light modes are contained in this app report.
There are upcoming developments which may address your needs. Stay tuned.
If you can do so, please let me know more about your project and goals. This will help us in addressing your questions.
Best regards,
Pascal
Pascal,
Thank you for your prompt response and the helpful information your provided.
The project I am working on involves projecting customized light patterns onto a surface with various veins running across. We want to customize the light pattern outputted by the PicoProjector to trace any given vein segment on the surface. Therefore, control over individual pixel would be great.
We are using a Beagleboard xM as the input for the PicoProjector. Do you know if the HDMI (DVI) hardware on the Beagleboard xM is capable of outputting 1440 Hz signal? If so, does the current driver (DSS2?) provide any interface for such task?
Once again, thank you very much for your support.
Tommy
Thank you for saying what your project involves. Very interesting.
I understand that "control over individual pixel" would make it easier for applications such as this. Unfortunately, that is not available in a direct way with the Pico chipset. It is possible to emulate individual pixel control from user space at the frame by frame level, though - as already pointed out. The composition of each frame is entirely up to the user when the Pico is in the external input modes.
I can not offer an answer for your question about the BeagleBoard HDMI at 1440 Hz. However, I can say that the Pico Kit v2 requires 60 Hz video formatted frames ONLY. The conversion to the higher rate subframes takes place internally. In other words, there is no means to send 1440 fps video to the Pico DLPC100 controller, even if the HDMI channel supported it. I hope this resolves some confusion about how the Pico chipset works.
Thank you for clarifying the fact that the pico projector only takes in 60Hz input.
I am not sure I understand the external pattern completely from the description on the structured light app note. Could you give me some more detailed explanation? When it says "1440 Hz" what is being changed at that rate?
Thank you and Best Regards,
Good question. Just as a review, the Pico Kit v2 (DLP1700 chip set) has 2 structured light modes: external and internal.
In the internal mode, the patterns are coming from inside the chipset and are selected and sequenced according to the procedures presented in the App Report Using the DLP Pico 2.0 Kit for Structured Light Applications (http://www.ti.com/lit/an/dlpa021a/dlpa021a.pdf).
In the external mode, the patterns are coming from an external source (in this case, the BeagleBoard) in the form of 60 fps 640x480 video over the Pico Kit v2's HDMI input port. The App Report referenced above also gives the steps needed to set up this mode. Notice that one of the steps sets the Pico Kit up to only use the upper left hand corner of the supplied video frame - or cropped VGA to HVGA (see figure 2). The pattern you want to display must be in this section of the VGA frame.
Also, there are several modes of external SL: see table 3. In each mode, the bits of the incoming video signal, which are formatted as RGB888, will be interpreted differently. In the 1 bit mode (the 1440 Hz mode) there are 24 equally timed binary frames during the period of each 60 Hz frame (24 x 60 = 1440).The RGB888 input (24 bits) will just be interpreted as a string of 24 bits for each pixel location. For each of the 24 "sub-frames" each pixel will be on/off (white/black) according to the corresponding bit value (1/0) in the RGB pixel value. This allows 24 distinct binary pixel patterns in each 60 Hz frame, or 1440 binary frames per second.
Again, the App Report (dlpa021a.pdf) has helpful timing diagrams and useful information.
I hope this makes it a bit clearer.
Hi Pascal,
I know it has been a while, but could you help me clarify the following?
In the external pattern 1440Hz mode, there are 1440 binary frames, each last about 1/1440 = 0.694ms
Data will be sent to the picoprojector every 1/60 = 0.0167s. Let's say a "piece" of data is sent very 0.0167s. Is each "piece" a sequence of 640x480x24 = 7372800 bits where:
bit 0 is the value of pixel 0 for the 1st 0.694ms
bit 1 is the value of pixel 0 for the 2nd 0.694ms
...
bit 23 is the value of pixel 0 for the 24th 0.694ms
bit 24 is the value of pixel 1 for the 1st 0.694ms
bit 7372799 is the value of pixel (640x480=)307200 for the 24th 0.694ms
Is that correct or did I totally misunderstand?
Regards,
Hi again, Tommy,
The way you are describing it is probably unnecessarily complicated - at least conceptially.
For the Pico Kit v2 1440 fps mono structured light mode the data going to the Pico Kit over the HDMI video input is just a normal VGA (640x480) RGB888 (24 bit "color") video frame at 60 Hz frame rate. You will be constructing a 640x480 pixel array for each video frame - but the 1440 Hz SL mode will use only the upper left hand 480x320 partial frame in order to map directly one-to-one onto the mirror array of the DLP1700 DMD. It doesn't really matter what data you put into the rest of the 640x480 frame. However, you do always have to construct a full valid 640x480 RGB888 frame. Only the upper left hand 480x320 corner section of the pixels will actually be displayed during the SL mode zoom-in. See Fig. 2 in the Application Report Using the DLP Pico 2.0 Kit for Structured Light Applications (Rev. A) (dlpa021a.PDF) (available from http://www.ti.com/litv/pdf/dlpa021a).
Now, for each pixel in the 480x320 subframe there are 24-bits of pixel data - R8 G8 B8 ==> 24 bits, b0 - b23. For each successive 60Hz frame, the 1440 Hz SL mode simply creates 24 binary bit planes out of the 24 bits of data - b0 - b23 in sequence. See Fig. 5 of the AR.
During each 16.67ms "frame" time the SL mode runs through each of the 24 binary planes in sequence - allocating them each 1/24th of the frame time. 24 x 60 = 1440 binary fps.
Section 3.3 of the AR covers this process in detail.
I hope this helps. Remember - the Application Report mentioned above is your friend.
Thank you, Pascal.
So my current understanding is:
typedef struct {
char red; //bit23...bit16
char green; //bit15...bit8
char blue; //bit7...bit0
} pixel;
struct frame {
pixel px_array[640][480]; //only upper left 480x320 will be used
}
A "frame struct" is sent to the picoproj every 1/60 = 0.01667s. During each 0.01667s, the picoproj produces 24 "binary frames". The 1st "binary frame" is 480x320 in size where every pixel is a 0 or 1 depending on the value of bit23 for that "pixel struct".
Is that correct?
Nghia,
Yes - this is descriptively correct.
However, you are probably intending to send the video stream to the Pico V2 over the HDMI (DVI-D) connector. This means that the stream is encoded as a sequence of RGB888 video frames at 640x480. So, the construction of the pixels (and the "stacking" of the 24 bits for the subframes has to occur when you are building the individual frames - before they are streamed. The DVI receiver chip in the Pico V2 receives this digital video stream and applies it to the 24-bit RGB parallel data port of the DlPC100. Then, the 1440 Hz external SL mode interprets the 24 bits as the binary pixel values for the 24 SL subframes.
I hope this isn't confusing maters. Does this make sense?
Hi there! If you need some help , I have some software that will convert video from monochrom 1bit per color to rgb multiplexed 640*480 60hz video which will be interpreted as 1440 fps by the pico. The input video needs to be 640*480 .. Cheers Gav
Gavin,
Thanks for offering this to others. This is a exactly what we would like to see happen on this forum - sharing our experiences and offering help to others to get their DLP projects working.
I will also ask you for this software when I need it.
Hello Pascal
What is the slowest possible frame rate it is possible to run the internal structured light? I could not find it in the documentation ( I saw you can set either 1200 or 2400). are there any other options?
Kind regards,
Ohad
Ohad,
If you haven't already done so, please see the document http://www.ti.com/lit/an/dlpa021a/dlpa021a.pdf Using the DLP Pico 2.0 Kit for Structured Light Applications. In the internal pattern mode the two choices are 1200 and 2400 fps. You were correct. In the external structured light mode, the frame rate varies by bit depth. For 8-bit depth external patterns (that is, via HDMI) the frame rate is 120 fps.