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Smntk
Posts: 11
Joined: Sun Mar 31, 2019 11:11 am

Raspberry + WittyPi2 + picoprojector DLP2000

Sun Mar 31, 2019 11:20 am

Hi!

I connected my Raspberry to the pico-projector DLPDLCR2000EVM with no problem for an artistic project, following the instructions that I read in the Frederick Vanderbosch website (http://frederickvandenbosch.be/?p=2948), but I need to add an on/safe shutdown button.

After some problems trying to make my own circuit based on internet information, I decided to buy a Witty Pi 2 (http://www.uugear.com/product/wittypi2/). I installed the required software and opened the daemon.sh file that it installs to modify two pins configuration, because the DLP2000 projector need to use them. So, I changed the GPIO4 (Halt pin for Witty Pi) and the GPIO17 (LED pin for Witty Pi) to the GPIO27 and GPIO22 that are not going to be used by the projector. If I do a test with no projector connected everything works perfectly. It switches on and do a safe shutdown properly. When I connect the DLP 2000 to the WittyPi2 (which is connected to the Raspberry), but without configuring the config.txt file for the projector, it works perfectly. In this case, the projector shows only the splash screen (there is no data sent to it).

When I modify the /boot/config.txt file and the /etc/rc.local file and reboot the system for configure the Raspberry and let it use the projector, the problem appears: the system tries to switch on (you can see the red light in the Raspberry) and the projector shows the splash screen, but suddenly it switches off and you can't see any light in the Raspberry although the WittyPi2 white light is slowly blinking as it usually does when it is in "standby mode". It's like some signal switch off the system while it tries to switch on. You can press again the button for turn it on and the same thing happends.
Image

I'm a newbie in this area and don't know what is happening. Don't know what is going wrong. I were trying to identify what part of the code were responsible of the failure, and I found that in the /boot/config.txt file, there were a line that, if remain commented with the #, let the system to switch on and off, but with no image in the projector. The line appears marked in bold text:

dtoverlay=i2c-gpio,i2c_gpio_sda=23,i2c_gpio_scl=24,i2c_gpio_delay_us=2
# dtoverlay=dpi18
overscan_left=0
overscan_right=0
overscan_top=0
overscan_bottom=0
display_rotate=1
framebuffer_width=360
framebuffer_height=640
enable_dpi_lcd=1
display_default_lcd=1
dpi_group=2
dpi_mode=87
dpi_output_format=458773
hdmi_timings=854 0 14 4 12 480 0 2 3 9 0 0 0 60 0 32000000 3

If I take the power connector and plug it directly to the Raspberry, it can switch on but the projector shows no image. If I connect via VNC server and do a gpio readall, I can see this:
Image

Is there anyway to correct the configuration for using that on/off system? It is something indispensable for my project. Would be grateful if I have some help for fixing this system or for knowing an alternative if it's not possible.

Thanks in advance.

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Smntk
Posts: 11
Joined: Sun Mar 31, 2019 11:11 am

Re: Raspberry + WittyPi2 + picoprojector DLP2000

Mon Apr 01, 2019 6:17 pm

As "dtoverlay=dpi18" makes that GPIOs 0~21 are occupied by DPI output, I2C and serial interface will be invalid.

WittyPi2 uses I2C interface to talk to the RTC chip, and it detects system shutdown by monitoring the serial TXD pin. So, there could be some problems because they are lines that the DLP2000 is using.

My question is:

It seems posible to change the I2C pins to other pins, as Philip Hodgers did in his code: https://e2e.ti.com/support/dlp/f/94/p/651931/2395243
# Add support for software i2c on gpio pins
dtoverlay=i2c-gpio,i2c_gpio_sda=23,i2c_gpio_scl=24,i2c_gpio_delay_us=2


Is it possible to change the TxD pin (GPIO14) to other pin? I read that is not possible to do it to some of the unused pins GPIO27, GPIO22, GPIO25 and GPIO26. According to the manual (https://www.raspberrypi.org/app/uploads ... herals.pdf) in the page 102 you can see that you can only use this pins for TxD: GPIO14, GPIO32 and GPIO36. Where are the last two GPIO pins in the Raspberry Pi 3B+? If it is not possible to use them, is there any possibility to use some other pin or other hardware to reconnect the TxD serial line?

Thanks.

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rpdom
Posts: 14417
Joined: Sun May 06, 2012 5:17 am
Location: Chelmsford, Essex, UK

Re: Raspberry + WittyPi2 + picoprojector DLP2000

Mon Apr 01, 2019 7:58 pm

Smntk wrote:
Mon Apr 01, 2019 6:17 pm
Is it possible to change the TxD pin (GPIO14) to other pin? I read that is not possible to do it to some of the unused pins GPIO27, GPIO22, GPIO25 and GPIO26.
Correct.
According to the manual (https://www.raspberrypi.org/app/uploads ... herals.pdf) in the page 102 you can see that you can only use this pins for TxD: GPIO14, GPIO32 and GPIO36. Where are the last two GPIO pins in the Raspberry Pi 3B+?
They are not exposed externally. They are only available on the Compute Modules, which expose all 54 GPIOs.
If it is not possible to use them, is there any possibility to use some other pin or other hardware to reconnect the TxD serial line?
No. The only way to provide an alternative serial port is via a USB adaptor, or by using a bit-banging software driver, but that wouldn't work with WittyPi2

User avatar
Smntk
Posts: 11
Joined: Sun Mar 31, 2019 11:11 am

Re: Raspberry + WittyPi2 + picoprojector DLP2000

Tue Apr 02, 2019 5:29 pm

Thanks a lot, rpdom.
I have bought this USB device, hoping that it will work with the system:
https://www.amazon.es/gp/product/B07LCFVDVZ

I will receive it in 20 or 30 days. I'll post describing the process if I succeed.
Thanks.

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Smntk
Posts: 11
Joined: Sun Mar 31, 2019 11:11 am

Re: Raspberry + WittyPi2 + picoprojector DLP2000

Sun May 19, 2019 8:56 am

It's impossible for me to move the serial port to the pins of the USB UART that I have connected to the Raspberry Pi 3B+
I think I'm gonna quit from this project. It's like hitting a wall with nude hands over and over again.

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