waveshare 35b on raspberry 3 : speed and colors

Question

I'm trying to configure waveshare 35b touchscreen on raspberry 3. I have 2 problems :

• slow refresh rate
• inverted colors (black is white)

Here is my config, (I do not need touchscreen, so it is not configured) :

in config.txt
# enable touchscreen over SPI
device_tree_param=spi=on
dtoverlay=waveshare35b


cat /etc/modules-load.d/touchscreen.conf 
spi-bcm2835
flexfb
fbtft_device

cat /etc/modprobe.d/fbtft.conf 
options flexfb regwidth=16 init=-1,0xb0,0x0,-1,0x11,-2,250,-1,0x3A,0x55,-1,0xC2,0x44,-1,0xC5,0x00,0x00,0x00,0x00,-1,0xE0,0x0F,0x1F,0x1C,0x0C,0x0F,0x08,0x48,0x98,0x37,0x0A,0x13,0x04,0x11,0x0D,0x00,-1,0xE1,0x0F,0x32,0x2E,0x0B,0x0D,0x05,0x47,0x75,0x37,0x06,0x10,0x03,0x24,0x20,0x00,-1,0xE2,0x0F,0x32,0x2E,0x0B,0x0D,0x05,0x47,0x75,0x37,0x06,0x10,0x03,0x24,0x20,0x00,-1,0x36,0x28,-1,0x11,-1,0x29,-3 width=480 height=320
options fbtft_device name=flexfb speed=8000000 gpios=reset:25,dc:24 fps=60 txbuflen=32768

cat /etc/X11/xorg.conf.d/99-fbdev-tft35.conf 
Section "Device"
  #WaveShare SpotPear 3.5", framebuffer 1
  Identifier "WaveShare3.5"
  driver "fbdev"
  Option "fbdev" "/dev/fb1"
  Option "ShadowFB" "off"
EndSection

I've tried many configurations :

• changing fbtft_device speed
• using other overlay (piscreen)
• test fbtft_device bgr option

But in all cases color are inverted and refresh rate is very slow.

Here is my kernel :

uname -a
Linux a4h-rpi-coffee-machine 4.14.62-1-ARCH #1 SMP Fri Aug 17 05:43:55 UTC 2018 armv7l GNU/Linux

Something is unclear for me, in waveshare35b overlay we can see waveshare35b values for parameters init fps

these parameters are also set in /etc/modprobe.d/fbtft.conf for flexfb configuration. It would appear that loading and configuring flexfb fbtft_device is meaningless. waveshare35b overlay already loads and configure touchscreen. But when I remove /etc/modules-load.d/touchscreen.conf and /etc/modprobe.d/fbtft.conf no driver is loaded.

dmesg |grep graphics
dmesg |grep spi

does not return anything.

Moreover waveshare35b is not in device tree :

sudo ls -R /sys |grep wave

returns nothing. I've recompiled dtbo and copied it to /boot/overlays but it did not change anything.

EDITED : Many thanks @Dirk I've also tried to check logs with vcdbg (to get it on arch :

wget -O vcdbg 'https://github.com/raspberrypi/firmware/blob/master/hardfp/opt/vc/bin/vcdbg?raw=true' && chmod 0755 vcdbg

and got :

002173.385: Failed to load overlay 'waveshare35b'
002173.484: brfs: File read: /mfs/sd/overlays/waveshare35b.dtb
003251.012: gpioman: gpioman_get_pin_num: pin EMMC_ENABLE not defined
003361.706: Device tree loaded to 0x2eff9900 (size 0x66b6)

Now I'm investigating it.

Answer 1

SOLUTION :

Loading manually:

spi-bcm2835
flexfb
fbtft_device

is meaningless. You just have to load waveshare35b in device tree, it will load

spi-bcm2835
flexfb
fbtft_device

with correct parameters. So you just have to follow steps described [here][2]

I was unable to load waveshare35b as we can see in first EDIT vcdbg logs. Problem was waveshare35b overlay name, I got a /boot/overlays/waveshare35b-overlay.dtbo if you load waveshare35b in config.txt, it must be /boot/overlays/waveshare35b.dtbo

Now, overlay is loaded as we can see :

sudo ./vcdbg log msg 2>&1 |grep wave
002167.283: brfs: File read: /mfs/sd/overlays/waveshare35b-overlay.dtb
002182.544: Loaded overlay 'waveshare35b'

Now, screen colors are fine, screen fps is quite slow.

I tried to speed up display with this config :

dtoverlay=waveshare35b:speed=32000000,fps=60

no I get :

 dmesg |grep graphics                                                                                                                                                                                                                           
[    7.845964] graphics fb1: fb_ili9486 frame buffer, 480x320, 300 KiB video memory, 32 KiB buffer memory, fps=100, spi0.0 at 32 MHz