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Re: Gert's VGA add-on for the B+

Posted: Wed Oct 14, 2015 7:16 pm
by dom
WalkToFreedom wrote: framebuffer_width=320
framebuffer_height=240
hdmi_group=1
hdmi_mode=8
The hdmi mode is 720x240. Default overscan adjustment is 32 pixels on each side, so you have 656x176 usable pixels. You can reduce the overscan if more pixels are visible.
Your framebuffer_width/framebuffer_height settings are going to cause a resize of the framebuffer, and so introduce some blurring.

Now I'm not sure if MAME is using the framebuffer, or a dispmanx overlay. If it is using the framebuffer then you probably don't want the framebuffer_ lines in config.txt or you will get resize blurring.

Re: Gert's VGA add-on for the B+

Posted: Thu Oct 15, 2015 10:23 pm
by WalkToFreedom
Hi Dom. Thanks for your reply. That would explain why everything did appear stretched. I commented out the framebuffer lines and it removed the stretching but now everything runs in a narrow band (should have taken a photo) about 1/3 of screen size centred in the middle of the CRT. i.e (@ = graphics, dash = blank)

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[email protected]@@@@@-------+
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[email protected]@@@@@-------+
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I'm using the RetroPie distro with AdvanceMAME which apparently uses modelines to generate the original game resolution, but all the games appear as above.

Did I read somewhere the video output from the HDMI is limited to a certain standardised range. I.e if I did this it would not work?:

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hdmi_cvt=256 224 60 1 1 0 1
hdmi_group=1
hdmi_mode=60

Re: Gert's VGA add-on for the B+

Posted: Tue Nov 10, 2015 9:12 pm
by tdicola
Anyone know did the 4.1 kernel in Jessie break or change anything in regards to using a DPI display? I'm having a lot of trouble using a modified dt-blob.bin with a DPI display on Jessie unfortunately. Same display and setup works perfectly with the 3.18 kernel in Wheezy, so it's not the hardware side of things. Curious if anyone has run into similar trouble and has any pointers.

Re: Gert's VGA add-on for the B+

Posted: Tue Dec 01, 2015 1:20 pm
by aBUGSworstnightmare
tdicola wrote:Anyone know did the 4.1 kernel in Jessie break or change anything in regards to using a DPI display? I'm having a lot of trouble using a modified dt-blob.bin with a DPI display on Jessie unfortunately. Same display and setup works perfectly with the 3.18 kernel in Wheezy, so it's not the hardware side of things. Curious if anyone has run into similar trouble and has any pointers.
Same here! I also think that either the code changed or this viewtopic.php?p=622498#p622498 is wrong.
When displaying gradients the picture reveals a problem (which you can not see from normal Pictures); Looks like two LSB were wrong or di not Change at all.

I also noticed that you can run into Troubles when compiling the device tree blob on a different HW-Version (i.e. compiling on 2 and using on B+).

Re: Gert's VGA add-on for the B+

Posted: Tue Dec 29, 2015 3:42 pm
by patryk105
Guys, I have bought a Chinese version of Gert's VGA add-on on dx.com, and to make it work I had to add the line "dtoverlay=vga666" to config.txt additionally to what is described in the manual of Gert's VGA add-on. Maybe it is useful to add this to the manual.
Btw I used a fresh install of NOOBS.

Greetz,
patryk105

Re: Gert's VGA add-on for the B+

Posted: Mon Feb 08, 2016 10:02 am
by PR77
Hi All,

Since getting the DPI interface working with some nice 5 Inch LCDs I have subsequently tired some 4.3 Inch LCDs with a higher resolution. Furthermore, I am now running Raspbian Jessie and the DPI configurations don't seem to work anymore! Anyone else have issues with Jessie? I am keen to see working config.txt's.

my GPIO_LIST is always;
0 INP INP ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2
10 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2
20 ALT2 ALT2 INP INP INP INP INP INP ALT0 ALT0
30 INP OUT OUT INP INP INP INP INP OUT INP
40 ALT0 OUT INP INP ALT0 ALT0 INP OUT ALT3 ALT3
50 ALT3 ALT3 ALT3 ALT3 INP
Thx!

Re: Gert's VGA add-on for the B+

Posted: Mon Feb 08, 2016 11:36 am
by 6by9
PR77 wrote:Hi All,

Since getting the DPI interface working with some nice 5 Inch LCDs I have subsequently tired some 4.3 Inch LCDs with a higher resolution. Furthermore, I am now running Raspbian Jessie and the DPI configurations don't seem to work anymore! Anyone else have issues with Jessie? I am keen to see working config.txt's.

my GPIO_LIST is always;
0 INP INP ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2
10 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2
20 ALT2 ALT2 INP INP INP INP INP INP ALT0 ALT0
30 INP OUT OUT INP INP INP INP INP OUT INP
40 ALT0 OUT INP INP ALT0 ALT0 INP OUT ALT3 ALT3
50 ALT3 ALT3 ALT3 ALT3 INP
Thx!
DPI support should be independent of distro as it is a firmware feature.
Check your firmware is up to date. GPIO 0&1 will be set to ALT0 during GPU boot to detect a HAT over I2C, but should now be put back to the mode listed in the dt-blob.bin (https://github.com/raspberrypi/linux/issues/1144)
VGA666 does not require GPIOs 0&1, so don't rely on the VGA666 overlay to set those pins to ALT2.

Re: Gert's VGA add-on for the B+

Posted: Mon Feb 08, 2016 6:22 pm
by PR77
6by9 wrote:
PR77 wrote:Hi All,

Since getting the DPI interface working with some nice 5 Inch LCDs I have subsequently tired some 4.3 Inch LCDs with a higher resolution. Furthermore, I am now running Raspbian Jessie and the DPI configurations don't seem to work anymore! Anyone else have issues with Jessie? I am keen to see working config.txt's.

my GPIO_LIST is always;
0 INP INP ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2
10 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2 ALT2
20 ALT2 ALT2 INP INP INP INP INP INP ALT0 ALT0
30 INP OUT OUT INP INP INP INP INP OUT INP
40 ALT0 OUT INP INP ALT0 ALT0 INP OUT ALT3 ALT3
50 ALT3 ALT3 ALT3 ALT3 INP
Thx!
DPI support should be independent of distro as it is a firmware feature.
Check your firmware is up to date. GPIO 0&1 will be set to ALT0 during GPU boot to detect a HAT over I2C, but should now be put back to the mode listed in the dt-blob.bin (https://github.com/raspberrypi/linux/issues/1144)
VGA666 does not require GPIOs 0&1, so don't rely on the VGA666 overlay to set those pins to ALT2.
Thanks for point me in the right direction. I've tried your overlay and it now seems to be configuring GPIO0 and GPIO1 correctly. However I am having difficulties again with the hdmi_settings. It seems that with some configuration the DPI does not active (i.e., I see no signals on my oscilloscope). Is there some kind of plausibility check on the configurations? The LCD I am now using is based on the LQ042T5DZ series.

Thx

EDIT: Just tried hdmi_cvt and a much better result has been observed. Will keep you posted once I have the over / under scan sorted out! :)

Re: Gert's VGA add-on for the B+

Posted: Mon Feb 08, 2016 8:44 pm
by 6by9
PR77 wrote:Thanks for point me in the right direction. I've tried your overlay and it now seems to be configuring GPIO0 and GPIO1 correctly. However I am having difficulties again with the hdmi_settings. It seems that with some configuration the DPI does not active (i.e., I see no signals on my oscilloscope). Is there some kind of plausibility check on the configurations? The LCD I am now using is based on the LQ042T5DZ series.

Thx

EDIT: Just tried hdmi_cvt and a much better result has been observed. Will keep you posted once I have the over / under scan sorted out! :)
I never got my overlay to work - it seemed to do the same thing as the dt-blob.bin on pinmuxing, but didn't work with the display. I didn't work out if it was termination or drive setting that were the issue. I've switched to the official display now, so didn't follow it up.

Re: Gert's VGA add-on for the B+

Posted: Tue Feb 09, 2016 8:09 pm
by PR77
Quick update: Over and under scan aren't looking the most promising. I can get the top of the screen image aligned but the bottom is proving to be more difficult; no matter what I change the overscan_bottom to, it doesn't seem to change anything.

Another thing I would like to get feedback on is the framebuffer_width/_height. Whenever I uncomment these so that the Width and Height are 480 and 270 respectively I only see a blank screen. This has got me really puzzled!

My basic configuration is as follows;
# uncomment the following to adjust overscan. Use positive numbers if console goes off screen, and negative if there is too much border
#overscan_left=1
#overscan_right=168
overscan_top=18
overscan_bottom=-31

# uncomment to force a console size. By default it will be display's size minus overscan.
#framebuffer_width=480
#framebuffer_height=270

# for more options see http://elinux.org/RPi_config.txt
dtparam=spi=off
dtparam=i2c_arm=off
dtoverlay=dpi-display #Thanks to 6by9!

enable_dpi_lcd=1
display_default_lcd=1
dpi_group=2
dpi_mode=87

#hdmi_timings configuration notes - For SHARP LCD
#h_active_pixels = 480
#h_sync_polarity = 0
#h_front_porch = 2
#h_sync_pulse = 5
#h_back_porch = 20
#v_active_lines = 270
#v_sync_polarity = 1
#v_front_porch = 2
#v_sync_pulse = 2
#v_back_porch = 31
#v_sync_offset_a = 0
#v_sync_offset_b = 0
#pixel_rep = 0
#frame_rate = 50
#interlaces = 0
#pixel_freq = 480 * 270 * 60 = 7776000
#aspect_ratio = 3

dpi_output_format=262165 #corrected h+v sync polarity and phase.
#hdmi_timings=480 0 2 5 20 272 1 2 2 31 0 0 0 60 0 7776000 3
hdmi_cvt=480 270 60 3
Any ideas?!?

Re: Gert's VGA add-on for the B+

Posted: Thu Feb 11, 2016 8:15 pm
by PR77
Hi all,

Any ideas with the Framebuffer issue? When I display the rgb_test.jpg I only see part of the image so it seems the physical screen resolution is not being handled by the OS. Hummm. This is where I am lost! :(

Re: Gert's VGA add-on for the B+

Posted: Sat Feb 13, 2016 6:20 am
by weetit
I have put DPI dot_clk on oscilloscope no matter what I set the dot_clk frequency has never go below 25MHz. I think this is the reason why it has problem with small LCD. Are there any of you can change it?

Re: Gert's VGA add-on for the B+

Posted: Sun Feb 14, 2016 2:42 pm
by PR77
weetit wrote:I have put DPI dot_clk on oscilloscope no matter what I set the dot_clk frequency has never go below 25MHz. I think this is the reason why it has problem with small LCD. Are there any of you can change it?
Hi Weetit,

I had this issue when either hmdi_settings and/or the dpi_output_format was not correct. I suspect there is some kind of sanity check performed on the configuration contents but have not yet figured this out completely. I also noticed that the pixel clock was more sinusoidal than the expected square. Are you seeing this also?

Additionally, are you seeing a pixel perfect image on your screen?

Paul

Re: Gert's VGA add-on for the B+

Posted: Tue Mar 15, 2016 6:29 am
by aBUGSworstnightmare
The OS is able to display 480x272 pixels correctly; tested this with Ortustech COM43H4M09XLC.

Attached you will find my documentation, the related config.txt file and a compiled device tree blob which initializes the GPIO to 24-bit colour (mode7).
The blob is compiled for RPi 2 V1.1 on Jessie.

EDIT: The data sheet of the TFT module is here http://docs-europe.electrocomponents.co ... 0792e8.pdf
COM43H4M09XLC.zip
config.txt and connection documentation for Ortustech COM43H4M09XLC (480x272pixels, 24-bit colour)
(49.85 KiB) Downloaded 448 times
dtblob_RPi2V1_1.zip
Device tree source file and compiled blob for RPi2 on Jessie
(4.13 KiB) Downloaded 462 times

Re: Gert's VGA add-on for the B+

Posted: Sun Mar 20, 2016 8:14 pm
by Cybersyn
Can HSYNC+VSYNC or DEN+clock be moved to different pins to free up an I2C bus? I'm connecting a 40-pin TFT LCD, but I kind of need I2C too.

Re: Gert's VGA add-on for the B+

Posted: Sun Mar 20, 2016 8:21 pm
by Cybersyn
kirgene wrote:Hello,
What chip should I use to convert DPI to HDMI? I'd like to have two HDMI outputs.
I think the Texas Instruments TFP410 is what you are looking for.

Re: Gert's VGA add-on for the B+

Posted: Sun Mar 20, 2016 10:15 pm
by 6by9
Cybersyn wrote:Can HSYNC+VSYNC or DEN+clock be moved to different pins to free up an I2C bus? I'm connecting a 40-pin TFT LCD, but I kind of need I2C too.
No, they can't.

Re: Gert's VGA add-on for the B+

Posted: Sun May 29, 2016 7:05 pm
by sigmaris
I was able to use the VGA-666 board to display on a Phillips CM8833-II monitor, which was formerly used with an Amiga 500. The monitor takes RGB and HV-sync signals, and supports horizontal sync frequencies in the range of 15kHz, so it can only display 240p/480i type signals. The only predefined mode I could get to display a stable picture was dpi_group=1, dpi_mode=12 but the picture was severely squashed horizontally.

I then found http://forum.arcadecontrols.com/index.p ... msg1545662 which suggested that when driving DPI at low resolutions, the pixel clock has to be an integer division of 19.2MHz and suggested a custom hdmi_timings value for 336x252 resolution at 50Hz. I was able to get a usable picture using these settings:

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dtoverlay=vga666
enable_dpi_lcd=1
display_default_lcd=1
dpi_group=2
dpi_mode=87
hdmi_timings=336 1 10 30 34 252 1 15 3 42 0 0 0 50 0 6400000 1 # 336:252 6.4MHz progressive
By trial and error with different settings from http://www.epanorama.net/faq/vga2rgb/calc.html I was able to find another custom timings line that gave me 320x240 at 60Hz refresh rate:

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hdmi_timings=320 1 16 30 34 240 1 2 3 22 0 0 0 60 0 6400000 1 #240p
This works on my monitor, but it technically uses a horizontal sync frequency of 16 rather than 15kHz, so it might not work for everyone. I wasn't able to reduce the vertical front porch/sync pulse/back porch values any further without getting lines cut off at the top or bottom of the display.

I wasn't able to get any interlaced (~480i) modes to display a good picture. The interlaced mode from the linked post (500x375 with a 9.6Mhz pixel clock) showed a picture but the flicker was horrible, it looked as if every other frame was blank. I think the interlaced modes may require a pixel clock between 9.6 and 19.2 MHz, which doesn't seem to work over DPI. I wonder if this is a hardware limitation or just a problem with the firmware? This post: viewtopic.php?f=29&t=112735 seems to suggest it's a problem with how the firmware is configuring the clock source for DPI.

Re: Gert's VGA add-on for the B+

Posted: Sat Jun 18, 2016 4:11 pm
by avel
I want to share observation that i have after creating timings for DPI interface

Custom timings that i created is for Kenwood Car display with sRGB input. Normally it works great when i pass it though HDMI -> VGA converter, but for DPI it wont. Nothing on the osciloscope.
timing looks like this:

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hdmi_timings=480 1 29 35 66 234 1 4 10 18 0 0 0 60 0 9735600 7
Later i found that someone used pixel clock in vale 9.6MHz for low resolution screen, I changed to that value and DPI started

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hdmi_timings=480 1 29 35 66 234 1 4 10 18 0 0 0 60 0 9600000 7
Whats more interesting DPI also works with 4.8MHz, 19.2MHz, 32MHz (values like UART speed) Maybe you have any idea why DPI behave like that?

Re: Gert's VGA add-on for the B+

Posted: Thu Jul 21, 2016 5:23 am
by tony1tf
I know this is an old topic, but our Hackspace ( http://leicesterhackspace.org.uk ) has some new1024 X 768 LCD panels with 3.3V TTL interface ( LG Philips LM151X05 A3C1 15" ). We were wondering if we could make a video wall by driving them with Pi Zeroes. It occurred to me that the GPIO pins can perhaps interface direct to the TTL inputs of the panel, so the VGA DAC resistors are not needed. Question - are the drivers for the VGA add-on still compatible with the latest Pi Zero OS, and has anyone tried the above. All the posts in this thread were about VGA compatibility and I havn't yet found anything on direct LCD panel drive.

Re: Gert's VGA add-on for the B+

Posted: Thu Jul 21, 2016 6:12 am
by fruitoftheloom
tony1tf wrote:I know this is an old topic, but our Hackspace ( http://leicesterhackspace.org.uk ) has some new1024 X 768 LCD panels with 3.3V TTL interface ( LG Philips LM151X05 A3C1 15" ). We were wondering if we could make a video wall by driving them with Pi Zeroes. It occurred to me that the GPIO pins can perhaps interface direct to the TTL inputs of the panel, so the VGA DAC resistors are not needed. Question - are the drivers for the VGA add-on still compatible with the latest Pi Zero OS, and has anyone tried the above. All the posts in this thread were about VGA compatibility and I havn't yet found anything on direct LCD panel drive.
Irrelevant to this thread, anyway you will need a LVDS Controller Board and 12V 4A PSU like:

http://www.aliexpress.com/store/product ... 98856.html
.

Re: Gert's VGA add-on for the B+

Posted: Thu Jul 21, 2016 9:56 am
by 6by9
tony1tf wrote:I know this is an old topic, but our Hackspace ( http://leicesterhackspace.org.uk ) has some new1024 X 768 LCD panels with 3.3V TTL interface ( LG Philips LM151X05 A3C1 15" ). We were wondering if we could make a video wall by driving them with Pi Zeroes. It occurred to me that the GPIO pins can perhaps interface direct to the TTL inputs of the panel, so the VGA DAC resistors are not needed. Question - are the drivers for the VGA add-on still compatible with the latest Pi Zero OS, and has anyone tried the above. All the posts in this thread were about VGA compatibility and I havn't yet found anything on direct LCD panel drive.
Based on a quick reading of the datasheet I'm going to disagree with fruitoftheloom - LM151X05 is not an LVDS panel, so does not need an extra controller board.

The phrase you're after is DPI - Display Parallel Interface. VGA666 is reusing that with a simple resistor ladder DAC to generate the VGA signal.
Some starter links:
http://blog.reasonablycorrect.com/raw-dpi-raspberry-pi/
https://learn.adafruit.com/adafruit-dpi ... t/overview (although I'm not saying the Kippah's pinout is compatible with your panel).
viewtopic.php?f=107&t=140125
There is also a device tree overlay "dpi-display" to configure the GPIOs in almost the same way as the VGA666 but including the two extra clock and enable signals on GPIOs 0&1.

If you're after more support on that, please start a new thread as it is really off-topic for this thread.

Re: Gert's VGA add-on for the B+

Posted: Thu Aug 18, 2016 5:28 pm
by steffensq
Hello,

I am attempting to generate custom hdmi timings for the DPI interface and I'm having an issue generating a custom pixel clock. From my understanding, by default the 19.2MHz oscillator is used for the pclk. For smaller frequencies, integer and frequency division may be applied through the clock manager registers to obtain smaller values such as the ones previously reported 9.6MHz, 6.4MHz, and 4.8MHz.

My issue is that I need a frequency larger than 19.2MHz for my panel. Can this be accomplished?
For reference, the frequency I am trying to obtain is 27MHz. I don't want to assume, but I feel as though this should be achievable given a faster frequency(32MHz) is being produced by the GPIO clock with custom timings.

From what i've found, the clock sources are as follows:

Oscillator - 19.2MHz
PLLA - 0Hz
PLLC - 1GHz
PLLD - 500MHz
HDMI - 216MHz

Which clock source is the 30 - 32 MHz pclk being generated from?
Can another clock source be assigned to GPIO0/SDA0 outside of the oscillator with DPI enabled?
Also, are the frequencies available for the DPI interface fixed based on CEA/DMT timings?

Any help would be much appreciated.

Best regards,
Steffensq

Re: Gert's VGA add-on for the B+

Posted: Sun Aug 28, 2016 5:26 pm
by michasanyi
Dear Sirs,

I'm new on this forum. I apologize if my questions are answered already somewhere later, but I couldn't read through all topics and posts yet.
I bought my Pi Zero a couple of month ago and I find it awesome. Then I found Gert's VGA666 board - it is also excellent - and I managed to use it with my old VGA monitor. Now I would like to use Red Bear's IoT pHAT as well but its pins on GPIO are in conflict with VGA666 pins.
I'm wondering if it is possible to reduce number of required pins of the VGA board still keeping the color resolution of 666 (or even 888). The solution could be building a new VGA interface board which contains an FPLD circuit in between GPIO pins of Raspberry and passive D/A converter resistor ladder. The red, green and blue components have to be output on the same set of GPIO pins out of Raspberry: first red, followed by green and blue components. This assumes a clock signal too of which frequency is double of pixel clock (its rising and falling edges are synchronized with color compnents and write the them into the FPLD). The RGB components are latched into the FPLD serially and gated out at once.
My questions are:
1. In the overlay definition file it is possible to set dpi_mode and dpi_group, but I couldn't find a list of possible values and what those mean. Is there a dpi_group/dpi_mode combination with which the RGB components are output time-multiplexed on the same GPIO pins?
2. Is it possible to get the doubled pixel frequency clock on another GPIO pin?
3. Is it possible to move HSYN and VSYN to other GPIO pins in order to build a real HAT?

Any help would much appreciated.

Best regards,
Sanyi

Re: Gert's VGA add-on for the B+

Posted: Sun Aug 28, 2016 5:53 pm
by mahjongg
All answers can be found in this document:
https://www.raspberrypi.org/documentati ... herals.pdf

Paragraph 6.2

when/if you have figured it out post your conclusions here, so that others do not have to do their own research, even when the result is negative!