So, I have a sharp LQ038Q5DR01 lcd, and tried to use dpi connection. All looks good except grey scale colors. Tried a lot of configurations but result is the same. Problem is the same as yours,
but I do not use any breadboard, raspberry pi 2 and lcd connected with 20cm(I think) wires.
Here is my images https://goo.gl/photos/KZwVV4gBNXahSyiD7
Could it be that wires are too long ? I dont have shorter to try. What other problems could be ?
Btw, lcd itself is 18bit color, but custom exposed 40pin connector(came with lcd) uses 16bit(rgb 565)

Here is my config.txt

gpu_mem_1024=256
hdmi_ignore_cec_init=1
disable_overscan=1
start_x=1
#dtoverlay=lirc-rpi
disable_splash=0
gpu_mem_256=112
#sdtv_aspect=0
#dtparam=gpio_in_pin=18
gpu_mem_512=144
#dtparam=gpio_out_pin=17
#dtoverlay=spi-bcm2835-overlay

###
# For use with the adafruit 5′ tft only.
##

dtparam=spi=off
dtparam=i2c_arm=off
dtoverlay=dpi24

#overscan_left=0
#overscan_right=0
#overscan_top=0
#overscan_bottom=0

framebuffer_width=320
framebuffer_height=240
#test_mode=1

enable_dpi_lcd=1
display_default_lcd=1
dpi_group=2
dpi_mode=87
dpi_output_format=19

hdmi_timings=320 0 0 0 72 240 0 0 0 5 0 0 0 0 0 3840000 1

This is an excellent post. Thank you very much.

I would like to use this VGA interface but I would like to use Red Bear’s IoT pHAT as well with Raspberry Zero. And this is the problem: their pins do not fit together.

I have another idea to add a VGA interface to the Raspberry Pi and I would like to know what is your opinion about it. In the original VGA666 there are 18 pins used to output the three color components plus HSYN and VSYN, in total of 20 pins. My idea is to multiplex the color components on only 6 (or 8) pins and to add a clock output with twice of pixel clock.There is – of course – an additional FPLD integrated circuit on the board. The output of the FPLD feeds the D/A converter built with the resistor ladder. The FPLD contains five 6 (or 8) bit latches: two for red and green components and one for the blue. The two latches of the red and green components are connected in serial thus forming a two-stage chain. The first rising edge of the clock writes the red component into the input latch of the red chain, the first falling edge writes the green component into the input latch of the green chain, the second rising edge writes the blue component into the blue latch and in the same moment it transfers the red and green component from the first latch into the second one. Thus the three color components of a pixel are fed in the same moment into the input of the D/A converter.

The advantages of this solution are:
1. pixels are sharp
2. uses less pins than the original version.

This solution needs that red, green and blue pixel components be multiplexed inside the GPU onto the same GPIO pins and a double pixel frequency be provided from the GPU. And this is the point where I do not have enough knowledge. Is this possible to get with the device tree?

Could you tell me your opinion, please?

Best regards,
Aromo

– couldn’t figure out many of the variables that I need to calculate the config options…

Thanks in advance !

Thanks so much,
Nicola