PiBox

The build seems to work on the dev platform if I use the following command from a terminal window.

FRAMEBUFFER=/dev/fb1 startx

This is with the HDMI plugged in and acting as the default display. Touchscreen works but might be rotated incorrectly - the display is in landscape mode but touchscreen appears to be in portrait mode. I'll deal with the touchscreen later.

So now I need to see how I can force the TFT to be used at boot. I might need to use fbcon on the cmdline or con2fbmap 1 1. But mostly I just need to find out if there are one or two fb devices when HDMI is not plugged in, then set the X.org startup to use the correct device. This could be done, potentially, by using different xorg.conf files and specifying the TFT device conf like so.

Section "Device" 
        Identifier      "Allwinner A10/A13/A20 FBDEV" 
        Driver          "fbturbo" 
        Option          "fbdev" "/dev/fb1" 

        Option          "SwapbuffersWait" "true" 
EndSection

Oh look - someone else is doing exactly what I'm doing. This could be really helpful.

I have scripts to switch from HDMI to TFT and back, but they're hacks that just rerun startx. Exiting the xterm that gets started from that drops me back to the last startx. So running pibox-tft puts me on the TFT and exiting that puts me back on the HDMI.

That's good enough for testing purposes to get the rest of the display working but not a production method of swapping. I need either fbcp or con2fbmap apparently.

The current problem is the display size. Setting the framebuffer wxh did squeeze the width but not the height.

1. https://github.com/notro/fbtft/wiki
2. https://learn.watterott.com/hats/rpi-display/fbtft-install/
3. https://learn.watterott.com/hats/rpi-display/faq/
4. http://www.willprice.dev/2017/09/16/adventures-with-tft-screens-for-raspberry-pi.html
5. https://www.raspberrypi.org/forums/viewtopic.php?t=111817#p1041032
6. https://philipp-weissmann.de/touch-display-auf-raspberry-pi-mit-arch-linux/ (German)
7. https://forum.armbian.com/topic/13221-fbtft-with-device-tree-overlay-on-mainline/ (DTS info) #

Turns out the display is working just fine. All I need to do is add

FRAMEBUFFER=/dev/fb1
export FRAMEBUFFER

to /etc/init.d/S99UI and the UI starts on the small display. Running pibox-hdmi on there will launch the HDMI display, albeit at the width of the TFT display.

Now I need to test the touchscreen. I should use xinput-calibrate and ts-calibrate for this. I can also do:

TSLIB_FBDEVICE=/dev/fb1 TSLIB_TSDEVICE=/dev/input/event0 ts_test
TSLIB_FBDEVICE=/dev/fb1 TSLIB_TSDEVICE=/dev/input/event0 ts_calibrate

An initial attempt at ts_test locked up the screen. I'll need to write some simplified scripts to make this easier to rerun since there is no shell history to rerun commands in the dev platform.

For xinput-calibrate I should be able copy the output from the following into an xorg.conf file.

DISPLAY=:0.0 xinput_calibrator

This doesn't work either. I just get "No calibratable devices found". Might need to set an environment variable to find the correct input event file.

The touchscreen is on event4, which I can see by running evtest with no arguments which gives me a list of events with associated names. I need a way to identify the event file in a script - evtest is interactive (at least without arguments).

To get the names of the devices you need an ioctl, which is not easy to call via a shell script. evtest.c has the scan_list() function that I could add to piboxlib/ptools/<new tool> to handle this.

Added pbeventlist to piboxlib. Needs to be tested on hardware, then used with the TBD scripts that I can use to test the touchscreen.

Preparing to test I found I wanted to switch back and forth between the TFT and HDMI. LCDShow-hdmi does this for LCDShow, but it's much simpler than that.

1. Edit config.txt
   1. Comment out framebuffer_<width,height>
   2. Comment out dtparam=i2c_arm=on
   3. Comment out dtparam-spi=on
   4. Comment out dtoverlay=tft35a:rotate=90
2. Edit /etc/init.d/functions
   1. Change FRAMEBUFFER=/dev/fb1 to FRAMEBUFFER=/dev/fb0
3. Reboot

That FRAMEBUFFER change also requires using that variable in /etc/init.d/S99UI.

I need to edit pibox-hdmi to comment these out or uncomment to go back to TFT and then do the reboot.

It's annoying that a reboot is required, but at least I can edit directly on the device for testing purposes. Editing with the TFT is very difficult due to the very small display, which requires very small fonts to get enough visible to be useful.

FRAMEBUFFER would need to be used to manually edit the xorg.conf file, which needs a Device section like so:

Section "Device" 
        Identifier      "Allwinner A10/A13/A20 FBDEV" 
        Driver          "fbturbo" 
        Option          "fbdev" "/dev/fb1" 

        Option          "SwapbuffersWait" "true" 
EndSection

So I can either have a copy of this that is edited by the pibox-hdmi script or I can have two copies with ".hdmi" and ".tft" suffices which the script chooses to symlink to the real xorg.conf.