This is the first part of the development of Project Koyomi, read this blog post
for more.
The purpose of this Raspberry Pi hat is to test and play around with the
display of the Vaio P before further development of the motherboard.
The board uses Texas Instruments' SN75LVDS83B LVDS transmitter using the Pi's DPI signals to send video out to the display. I might consider dropping DPI and replacing it with a DVI receiver to free up the Raspberry's GPIO, but those ICs tend to be bulky so it'll be considered in the later stages of development.
The display connector is made by I-PEX, and the model numbers are
20374-030E-31/20374-R30E-31, they're the same but the 0 variant seems to be
more common.
The display, in my case a LT080EE04100 by Toshiba (it should be the same for
all Vaio Ps), has no backlight driver, and for that the backlight pins are
broken out, allowing testing of different drivers.
The driver will be controlled using software I2C since all the hardware I2C
pims are already used by DPI. The assigned GPIOs are 23 for SDA and 24 for SCL.
More info about software I2C on this page.
The current configuration being tested in config.txt (on top of the default)
is:
dtparam=i2c_arm=off
dtparam=spi=off
display_auto_detect=0
dtoverlay=vc4-kms-dpi-generic
dtparam=hactive=1600,hfp=32,hsync=65,hbp=97
dtparam=vactive=768,vfp=1,vsync=1,vbp=8
dtparam=width-mm=182,height-mm=87
dtparam=clock-frequency=83600000,rgb666
framebuffer_width=1600
framebuffer_height=768
dtoverlay=i2c-gpio,i2c_gpio_sda=23,i2c_gpio_scl=24
disable_overscan=1
Keep in mind the aforementioned issues with color reproduction.
Huge thanks to Arya (@CRImier) for her help during most phases of the design!
