Adafruit PiTFT 2.8" Capacitive Screen with Buttons (solved)

rlsten

I have been working on a number of ways of interfacing with Rune in some kind of portable enclosure using resistive screens, touchpads, etc. I've found that the resistive screens are somewhat difficult to operate, especially scrolling, and touchpads can too easily be triggered when in a bag or pocket. I have followed with great interest the threads here regarding the use of a simple LCD panel to display the currently playing music and hardware buttons to control the interface as a sort of compromise pending the availability of a small (3.5" or less) capacitive screen that works with Rune. So along those lines, I tried the Adafruit PiTFT 2.8" capacitive screen (No. 2423), which comes with 4 buttons supposedly mapped to 4 GPIO pins (17, 22, 23, 27).

So far, I have been able to get an image of RuneAudio on the screen with a Raspberry Pi 2 and Pi 3; however, as expected I have not been able to get the capacitive touch to work. I assume this is because Adafruit embedded the touch drivers in the kernel, and they can't be simply added to Arch.

The screen serves the purpose of displaying what is playing now, as in the excellent thread "LCD display and buttons in Python (tutorial and code)" #1191. But I am having trouble getting the 4 buttons to work. I tried the PeteB's script from #366514, using pin 17, which is supposedly mapped to one of the screen's buttons, but I got the following error:

File "hw_pause_play.py", line 10, in <module>
GPIO.setup(InputPin, GPIO.IN, pull_up_down=GPIO.PUD_UP)
ValueError: The channel sent is invalid on a Raspberry Pi

When I tried pin 22, I got the following message:

hw_pause_play.py:10: RuntimeWarning: This channel is already in use, continuing anyway. Use GPIO.setwarnings(False) to disable warnings.
GPIO.setup(InputPin, GPIO.IN, pull_up_down=GPIO.PUD_UP)
Traceback (most recent call last):
File "hw_pause_play.py", line 13, in <module>
GPIO.wait_for_edge(InputPin, GPIO.FALLING)
RuntimeError: Error waiting for edge

Also the "Stop" button on the display kept changing color.

When I used pin 7, it seemed like the script was working, but I don't know how to assign specific GPIO pins to the Adafruit buttons.

Can anyone tell me what I am doing wrong?

Thanks,
Rod

hondagx35

Hi Rod,

as expected I have not been able to get the capacitive touch to work.

Why as expected? Should be no problem to get it working.

First question is:
RP0, RP1 RP2/3?

What is the output from:

modprobe stmpe_ts

On the RP2/3 images this driver is loadable, so should be no problem to get the touch working.

Can anyone tell me what I am doing wrong?

You know about the difference between
- GPIO.setmode(GPIO.BOARD)
and
- GPIO.setmode(GPIO.BCM) ?
see here

Frank

rlsten

Frank, thanks for your suggestions. I think you have solved my button issue, but the touch screen is still a puzzle.

hondagx35 wrote Why as expected? Should be no problem to get it working.

Because the Adafruit people seem to be saying (although I could be misunderstanding them) that the screen will not work with any distribution other than raspbian without recompiling the kernel. See https://learn.adafruit.com/adafruit-2-8-pitft-capacitive-touch/software-install

First question is:
RP0, RP1 RP2/3?

RP2 and RP3

What is the output from:

modprobe stmpe_ts

nothing

On the RP2/3 images this driver is loadable, so should be no problem to get the touch working.

I saw that, and tried using that driver in 99-calibration.conf. Is there somewhere else I should be referencing that driver? In /boot/config.txt, I inserted the following:

# --- added by adafruit-pitft-helper Thu 31 Mar 11:25:42 UTC 2016 ---
[pi1]
device_tree=bcm2708-rpi-b-plus.dtb
[pi2]
device_tree=bcm2709-rpi-2-b.dtb
[all]
dtparam=spi=on
dtparam=i2c1=on
dtparam=i2c_arm=on
dtoverlay=pitft28c,rotate=270,speed=32000000,fps=20
# --- end adafruit-pitft-helper Thu 31 Mar 11:25:42 UTC 2016 ---

I copied the driver pitft28c-overlay.dtb to /boot/overlays from the Adafruit raspbian distribution. I also tried the pitft28-capacitive driver, and the screen worked, but not touch.

You know about the difference between
- GPIO.setmode(GPIO.BOARD)
and
- GPIO.setmode(GPIO.BCM) ?
see here

No, I didn't know about that!

My python script was using GPIO.setmode(GPIO.BOARD)
and apparently the numbers used by the screen were the BCM numbers. I went back and changed the number and it worked. Thanks very much, Frank!

Rod

hondagx35

Hi Rod,

i searched the /boot/overlays/README file on my RP2 (4.4.20-1) and found:

Name:   pitft28-capacitive
Info:   Adafruit PiTFT 2.8" capacitive touch screen
Load:   dtoverlay=pitft28-capacitive,<param>=<val>
Params: 
        speed                   Display SPI bus speed
        rotate                  Display rotation {0,90,180,270}
        fps                     Delay between frame updates
        debug                   Debug output level {0-7}
        touch-sizex             Touchscreen size x (default 240)
        touch-sizey             Touchscreen size y (default 320)
        touch-invx              Touchscreen inverted x axis
        touch-invy              Touchscreen inverted y axis
        touch-swapxy            Touchscreen swapped x y axis

So it should work without any driver installation.
I don't know if this is also available on the stock RP2 image.

If not, you can update the kernel:

pacman -Sy --force raspberrypi-firmware-bootloader linux-raspberrypi

delete the file /etc/modules-load.d/ras....conf

rm /etc/modules-load.d/raspberrypi.conf

add "dtparam=audio=on" to your /boot/config.txt

    # Uncomment one of these lines to enable an audio interface
    #dtoverlay=hifiberry-dac
    #dtoverlay=hifiberry-dacplus
    #dtoverlay=hifiberry-digi
    #dtoverlay=hifiberry-amp
    #dtoverlay=iqaudio-dac
    #dtoverlay=iqaudio-dacplus
    dtparam=audio=on

Frank

rlsten

Hi Frank,

I am getting closer to making the screen work (thanks again), but I am still doing something wrong. I have touch capabilities now by referencing the pitft28-capacitive driver in /boot/config.txt. However, I seem to only be able to make it work in portrait mode (rotate=180). When I use the settings for rotate=270, the axes are all screwed up. The bottom is on the left, the right is on the bottom, when I move my finger horizontally, it scrolls vertically, etc.

These settings for /etc/X11/xorg.conf.d/99-calibration.conf worked for rotate=180

Section "InputClass"
    Identifier "captouch"
    MatchProduct "stmpe_ts"
    Option "SwapAxes" "0"
    Option "InvertY" "0"
    Option "Calibration" "0 240 0 320"
EndSection

But these settings did not work for rotate=270:

Section "InputClass"
    Identifier "captouch"
    MatchProduct "stmpe_ts"
    Option "SwapAxes" "1"
    Option "InvertY" "0"
    Option "InvertX" "1"
    Option "Calibration" "0 320 0 240"
EndSection

These settings also didn't work (supposedly for rotate=90)

Section "InputClass"
    Identifier "captouch"
    MatchProduct "stmpe_ts"
    Option "SwapAxes" "1"
    Option "InvertY" "1"
    Option "Calibration" "0 320 0 240"
EndSection

I did modify /root/.config/midori/config by changing
last-window-width=800 to 320
last-window-height=480 to 240
zoom-level=0.77567797899246216 to .7

and I commented about user-stylesheet-uri=file:///root/.local/share/midori/styles/local-styles.css

so that the information fit better on the screen. I don't know if that screwed anything up, but it doesn't seem to affect the screen at 180.

Any idea what I'm doing wrong?

Rod

hondagx35

Hi Rod,

These settings for /etc/X11/xorg.conf.d/99-calibration.conf worked for rotate=180

And why not doing it as it should be done?
Use device tree parameters:

Name:   pitft28-capacitive
Info:   Adafruit PiTFT 2.8" capacitive touch screen
Load:   dtoverlay=pitft28-capacitive,<param>=<val>
Params:
        speed                   Display SPI bus speed
        rotate                  Display rotation {0,90,180,270}
        fps                     Delay between frame updates
        debug                   Debug output level {0-7}
        touch-sizex             Touchscreen size x (default 240)
        touch-sizey             Touchscreen size y (default 320)
        touch-invx              Touchscreen inverted x axis
        touch-invy              Touchscreen inverted y axis
        touch-swapxy            Touchscreen swapped x y axis

Frank

rlsten

Thanks, Frank.

I didn't know that 99-calibration.conf did not control touch with this screen. So, the code below in /boot/config.txt provides for proper touch where the buttons are on the left of the screen in landscape mode:

# --- added by adafruit-pitft-helper Thu 31 Mar 11:25:42 UTC 2016 ---
[pi1]
device_tree=bcm2708-rpi-b-plus.dtb
[pi2]
device_tree=bcm2709-rpi-2-b.dtb
[all]
dtparam=spi=on
dtparam=i2c1=on
dtparam=i2c_arm=on
dtoverlay=pitft28-capacitive,rotate=270,touch-swapxy,touch-invy,speed=32000000,fps=20
# --- end adafruit-pitft-helper Thu 31 Mar 11:25:42 UTC 2016 ---

hondagx35

Hi rlsten,

So, the code below in /boot/config.txt provides for proper touch where the buttons are on the left of the screen in landscape mode:

Is this a question, or can we mark the thread as solved?

Frank

rlsten

Solved.