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DLPDLCR2000EVM: connection to Raspberry Pi 4 Model B

Andreea Bunica
Prodigy 50 points
Part Number: DLPDLCR2000EVM

Hi! 

I've been trying to connect my DLP lightcrafter to a Raspberry Pi 4 model B. I am attaching the exact tutorial and steps that I followed: 

The only difference to the tutorial attached is that I'm powering the DLP and the Pi separately, as the power supplied by the DLP isn't enough to turn on my Pi, and it gets stuck in a loading screen. So I've removed the GND, 5V and pin 6 to J3 pin connections from my circuit. Everything else is the same. 

I've modified the /boot/config.txt file with all the settings specified in the tutorial. 

When I have the DLP and Pi wired and powered on: 

> the DLP displays the normal splash screen (same as when I power it on on its own)

> the Pi displays the load screen, the boot screen asking if you want to go into recovery mode and then, when it's supposed to go into booting the OS, the display turns black and nothing else happens. (meaning I am unable to even check if the i2c device is read)

I tried: 

> deleting the modifications on the /boot/config.txt > the pi boots up normally even tho it's wired to the DLP

> without the config.txt  modifications, I tried checking if the i2c device is being detected; I am only receiving an empty matrix; 

I was thinking that this could have to do with the slightly changed GPIO on Pi 4 model B? I am not sure if it could be something like this or if I am doing something wrong. 

  • 0
    TI__Expert 3360 points

    Hi Andreea, 

    Welcome to the TI E2E forums and thank you for your interest in DLP. 

    For troubleshooting the setup, I recommend the following steps:

    1. Ensure that the jumpers are placed correctly. There are 27 connections and it can be easy to misplace them.

    2. Ensure that the Raspberry Pi (Rpi) and DLPDLCR2000EVM are at the same voltage levels by connecting the Rpi GND to the EVM GND, as well as connecting the Rpi +5V to the EVM +5V. This can be achieved by connecting the Rpi P2_6 to pin #1 of the EVM J3. This will make sure that communication can occur between the two devices. 

    3. The /boot/config.txt modifications ensure that the pinouts referenced on Frederick Vandenbosch's website are set on the raspberry pi. You will be able to check i2c device connections after making these modifications and rebooting the system.

    Please let me know if these resolve the issue.

    Thank you,

    Chris

  • 0 in reply to Cody Smith
    Prodigy 50 points

    Actions done: 

    1. Re-wired the connections

    2. Connected Rpi Gnd to EVM Gnd & wired the 5V via pin 6- J3. 

    3. The config files are in my /boot/config.txt 

    I have to mention that my DLP and Raspberry Pi are powered separately. The DLP is powered via the recommended AC-DC 5V converter, and the Raspberry Pi is connected to a C type 5v-3a phone charger. If I try powering them on through the same power supply, one of them doesn't turn on. 

    With the J3 connection on, when I run > sudo i2cdetect, I receive no signal from the EVM. 

    Without J3, I get the following values: 

    I then ran:

    sudo i2cset -y 3 0x1b 0x0c 0x00 0x00 0x00 0x13 i

    sudo i2cset -y 3 0x1b 0x0b 0x00 0x00 0x00 0x00 i
     
    And without the J3 connection, the DLP displays the following: 

    If I instead connect it to the J2 pin, the DLP displays: 

  • 0 in reply to Andreea Bunica
    TI__Expert 3360 points

    Hi Andreea,

    I will look more into this and get back to you soon.

    Thank you,

    Chris

  • 0 in reply to Andreea Bunica
    TI__Expert 3360 points

    Hi Andreea,

    I noticed in the photo sent that the red jumper is connected to the larger pinout header. The +5V pin of the EVM will be located on J3, pin#1. Please see the schematic here for reference: 

    Similarly, it is possible that the connections made between the raspberry pi and the EVM are misplaced. I recommend reviewing the connections and referencing both the raspberry pi pinout and EVM schematic above. 

    Once the EVM displays its splash screen, and i2c connection is made, you may need to search all i2c buses to see where the EVM has been placed. The i2cdetect showing all addresses taken is indicative of SCL and SDA being swapped. 

    Thank you,

    Chris

  • 0 in reply to Cody Smith
    Prodigy 50 points

    Hi Chris, 

    Just an update- I tried swapping the SDA and SCL wires as you suggested, but I am still getting all the addresses when I do i2cdetect. I am not sure why this is happening. Even with this error, I have since gotten the projector to display Pi's screen accordingly by changing my /boot/config.txt parameters following this case: 

    But I am facing the same issue as the same issue as mentioned in there as well- my color banding is very glitchy. It seems particularly sensitive to white, and the screen starts shaking quite badly if I have any white pixels on the screen; same with the mouse cursor and when I try to open any folders on the Pi's desktop, the entire desktop glitches and then restarts, without opening anything.  

  • 0 in reply to Andreea Bunica
    TI__Mastermind 28005 points

    Andreea,

    The issue you are seeing (banding) is almost definitely a video timing problem. The GPIOs on the Raspberry Pi struggle to deliver the appropriate amount of current depending on how they are connected to deliver video content. If you probe some of the video signals, you will probably see the VSYNC or pixel clock being too weak to produce a good signal.

    This issue becomes most apparent when using jumpers (instead of an adapter PCB or a short ribbon cable) and especially so when said jumpers are long.

    Here are some tips to make the video look good on the Raspberry Pi:

    > Reduce the pixel clock output from the Raspberry Pi (lower is easier for the RPi to drive)

    > Reduce the length of the jumpers (or replace them with an adapter board such as on this page https://www.mickmake.com/post/build-a-pi-zero-w-pocket-projector-project/ for a more decisive solution) 

    > Adjust the GPIO drive strength. Do "gpio drive 0 <X>" in command line where <X> is a value from 0 to 7. (See https://www.raspberrypi.org/documentation/hardware/raspberrypi/gpio/gpio_pads_control.md for more information)

    I hope this helps.

    Best Regards,

    Philippe Dollo