4DPI-32-II

4DPi-32-II Datasheet Revision 2.19 Copyright © 2023 4D Systems Content may change at any time. Please refer to the resource centre for latest documentation. Contents 1. Description 3 2. Features 4 3. Pin Configuration and Summary 5 4. Connecting the Display to the Pi 7 4.1. Hardware Connection 7 4.2. Software Download/Installation 8 4.3. Calibrating the Touch Screen 10 4.4. Change the Display Orientation 11 4.5. SPI Frequency and Compression 12 4.6. Backlight Control 13 4.7. Parameters Listing 14 4.8. HDMI or 4DPi Output 14 4.9. DPI Adjustment 15 5. Display Module Part Numbers 16 6. Latest Kernel Versions 16 7. Mechanical Details 17 8. Schematic Diagram 18 9. Specifications 19 10. Appendix 1 - Code Examples - Push Buttons 21 10.1. Example for communicating to Push Buttons, for C language 21 10.2. Example for communicating to Push Buttons, for Python language 22 10.3. Example for Shutdown and Reset buttons, for C language 24 10.4. Example for Shutdown and Reset buttons, for Python language 26 11. Revision History 4D Systems 28 DATASHEET Page 2 of 28 4DPi-32-II Description 1. Description The 4DPi-32-II (Revision 2.x Hardware) is a 3.2" Primary Display for the Raspberry Pi, which plugs directly on top and displays the primary output like what is normally sent to the HDMI or Composite output. It features an integrated Resistive Touch panel, enabling the 4DPi-32-II to function with the Raspberry Pi without the need for a mouse. Communication between the 4DPi-32-II and the Raspberry Pi is interfaced with a high-speed 48Mhz SPI connection, which uses an onboard processor for direct command interpretation and SPI communication compression, and features a customised DMA-enabled kernel. This combination allows this display to output 25FPS when displaying a typical image/video and can achieve higher depending on if the image can be compressed. The 4DPi-32-II is designed to work with the Raspberry Pi Operating System (previously named Raspbian) running on the Raspberry Pi, as that is the official Raspberry Pi operating system. It is also compatible with Pixel. Note • 4DPi-32-II Hardware states 4DPi-32 as the part number but is identifiable as the HW Rev of the PCB is 2.0 or above. • Raspberry Pi is a trademark of the Raspberry Pi Foundation, and all references to the words 'Raspberry Pi' or the use of its logo/marks are strictly about the Raspberry Pi product, and how this product is compatible with but is not associated with the Raspberry Pi Foundation in any way. 4D Systems DATASHEET Page 3 of 28 4DPi-32-II Features 2. Features • Universal 3.2" Primary Display for the Raspberry Pi. • Compatible with Raspberry Pi A+, B+, Pi2, Pi3, Pi3 B+, Pi4, Pi Zero, Pi Zero W and Pi Zero 2 W. Revision 2.x hardware is not compatible with older A or B models. • 320x240 QVGA Resolution, RGB 65K true-to-life colours, TFT Screen with integrated 4-wire Resistive Touch Panel. • Display full GUI output / primary output, just like a monitor connected to the Raspberry Pi • High -Speed 48MHz SPI connection to the Raspberry Pi, featuring SPI compression technology. • The typical frame rate of 25 Frames per second (FPS), is higher if the image can be compressed further by the kernel. Lower if no compression is possible. • Powered directly off the Raspberry Pi, no external power supply is required. • On/Off or PWM controlled backlight, selectable by onboard jumper. • On board EEPROM for board identification, following the HAT standard. • Module dimensions: 57.3 x 92.4 x 20.5mm (including corner plates). • Weighing ~ 55g. • Display Viewing Area: 48.60 x 64.80mm • 4x corner plates with 2.6mm holes for mechanical mounting. • RoHS and CE Compliant. 4D Systems DATASHEET Page 4 of 28 4DPi-32-II Pin Configuration and Summary 3. Pin Configuration and Summary P1 Pinout (Raspberry Pi Connector – Female Connector) Pin Symbol I/O 1 +5V P +5V Supply Pin, connected to the main 5V supply of the Raspberry Pi 2 +3.3V P +3.3V Supply Pin, connected to the main 3.3V supply of the Raspberry Pi. 3 5V P +5V Supply Pin, connected to the main 5V supply of the Raspberry Pi 4 SDA1 I/O 5 GND P Ground Pin, connected to the main system Ground of the Raspberry Pi 6 SCL1 O I2C SCL1 7 GPIO14 I/O GPIO on the Raspberry Pi - unused 8 GPIO4 I/O GPIO on the Raspberry Pi - unused 9 GPIO15 I/O GPIO on the Raspberry Pi - unused 10 GND P 11 GPIO18 I/O 12 PENIRQ I Interrupt for the touchscreen controller 13 GND P Ground Pin, connected to the main system Ground of the Raspberry Pi 14 KEYIRQ I Interrupt for the push buttons 15 GPIO23 I/O GPIO on the Raspberry Pi - unused 16 GPIO22 I/O GPIO on the Raspberry Pi - unused 17 GPIO24 I/O GPIO on the Raspberry Pi - unused 18 +3.3V P +3.3V Supply Pin, connected to the main 3.3V supply of the Raspberry Pi 19 GND P Ground Pin, connected to the main system Ground of the Raspberry Pi 4D Systems Description I2C SDA1 Ground Pin, connected to the main system Ground of the Raspberry Pi GPIO on the Raspberry Pi – Can be used for PWM Backlight, else unused DATASHEET Page 5 of 28 4DPi-32-II Pin Configuration and Summary Pin Symbol I/O Description 20 MOSI O SPI MOSI Pin 21 GPIO25 I/O 22 MISO I SPI MISO Pin 23 SPI-CS0 O SPI Chip Select 0 – Used for Xilinx Processor for Display, to Raspberry Pi 24 SCK O SPI SCK Clock Pin 25 SPI-CS1 O SPI Chip Select 1 – unused 26 GND P Ground Pin, connected to the main system Ground of the Raspberry Pi 27 ID-SC O I2C ID EEPROM 28 ID-SD I/O I2C ID EEPROM 29 GND P 30 GPIO5 I/O GPIO on the Raspberry Pi - unused 31 GPIO12 I/O GPIO on the Raspberry Pi - unused 32 GPIO6 I/O GPIO on the Raspberry Pi - unused 33 GND P 34 GPIO13 I/O GPIO on the Raspberry Pi - unused 35 GPIO16 I/O GPIO on the Raspberry Pi - unused 36 GPIO19 I/O GPIO on the Raspberry Pi - unused 37 GPIO20 I/O GPIO on the Raspberry Pi - unused 38 GPIO26 I/O GPIO on the Raspberry Pi - unused 39 GPIO21 I/O GPIO on the Raspberry Pi - unused 40 GND P GPIO on the Raspberry Pi - unused Ground Pin, connected to the main system Ground of the Raspberry Pi Ground Pin, connected to the main system Ground of the Raspberry Pi Ground Pin, connected to the main system Ground of the Raspberry Pi Note • I = Input, O = Output, P = Power • The onboard processor of the 4DPi-32-II uses one of the Chip Select(CS) pins on the Raspberry Pi's SPI Bus (SPI-CS0). There is SPI-CS1 still available for use by the User. • The on-board Touch Screen Controller utilises the I2C bus (SDA1, SCL1) to communicate to the Raspberry Pi. The SPI Bus can communicate with other devices also, so is not restricted only to the 4DPi's touch controller. 4D Systems DATASHEET Page 6 of 28 4DPi-32-II Connecting the Display to the Pi 4. Connecting the Display to the Pi 4.1. Hardware Connection The 4DPi-32-II is easily connected to a Raspberry Pi, by simply aligning the Female 40-way header with the Raspberry PI's Male 40-way header, and connecting them - ensuring the aligning is correct and all pins are seated fully and correctly. Note The 4DPi-32-II is supported only by the 40-way header, and therefore pressing on the touch screen may result in the 4DPi-32-II moving towards the Raspberry Pi, and therefore the circuitry touching the Raspberry Pi. This could result in damage to either product if a short circuit were to occur. It is therefore highly encouraged to mount the display and attach the Pi to the mounted display. If development is desired on the bench before the mounting of the display, please ensure some sort of support is provided between the 4DPi-32-II and the Raspberry Pi so they do not touch inadvertently. Included in the box is a small double-sided sticky rubber pad. This is optional, however, can be placed on the top of the Ethernet connector of the Raspberry Pi, to provide some support to the display. 4D Systems DATASHEET Page 7 of 28 4DPi-32-II Software Download/Installation 4.2. Software Download/Installation 4D Systems has prepared a custom DMA-enabled kernel for use with the Raspberry Pi Operating System (previously named Raspbian OS), which is available for download as a single package. This can be installed over your existing OS installation, or it can be applied over a fresh image. We recommend that you apply it over a fresh image. If you are starting from a fresh image, start from Step 1, or else skip to step 3 if you already have an OS image and want to apply this kernel to that. If you are not installing from a fresh image and you encounter issues, we won't know the settings of your OS so please try and use a fresh image to determine any modifications that conflict with our kernel release. If you are running an OS with a Kernel version later than our Kernel Pack, you might encounter problems. Please contact support if you have problems. If you already have a custom Kernel, then applying our Kernel Pack over your custom Kernel will likely stop your previous modifications from working. You will need to build the kernel from scratch using the steps below. STEPS (recommendations): 1. Install a fresh operating system as discussed on the Raspberry Pi website. Enable SSH and Wi-Fi as preferred. 2. Connect the 4DPi and insert the uSD card into the Raspberry Pi. You will need network connectivity to proceed with the installation. A monitor, keyboard and mouse are required if not using SSH. SSH can be configured in Step 1. Power on the Raspberry Pi and make sure it is connected to your network. 3. Login to the Raspberry Pi using the standard 'pi' and 'raspberry' credentials or as configured in Step 1. If SSH is not used, open the Terminal app. 4. You are welcome to perform a system update if prompted, but please take note that if you install a newer kernel than what our Kernel Pack offers, then you could encounter problems. Therefore, it's not advisable to update the system, as this could update the Kernel. 5. Typically, on modern versions of the Pi OS, this following step is not required or is done automatically. However, it is here for reference. Expand the file system on the downloaded image using raspi-config (submenu Expand Filesystem). After exiting raspi-config a reboot is needed. $ sudo raspi-config $ sudo reboot 6. Once rebooted, you need to do an apt-get upgrade , because doing this after applying the Kernel Pack will render the 4DPi modifications disabled. Please note that doing an upgrade could change your current Kernel which could make the version installed newer than the Kernel Pack you are about to install next. The Kernel pack must be applied to a kernel very close (a newer Kernel Pack is generally OK) if not identical to the kernel your OS is running, or there will be issues. 7. Log into your Raspberry Pi again, you will need to download and install the Kernel Pack which supports the 4DPi. The following step requires sudo root access. 4D Systems DATASHEET Page 8 of 28 4DPi-32-II Software Download/Installation 8. To download and install files, enter the following commands in terminal/shell/SSH to download the kernel from the 4D Systems Server: $ wget https://4dsystems.com.au/download/14644/ -O gen4-hats.tar.gz • Then extract the kernel pack: $ sudo tar --keep-directory-symlink -xzvf gen4-hats.tar.gz -C / • If you encounter issues running the above command, try adding --no-same-owner $ sudo tar --no-same-owner --keep-directory-symlink -xzvf gen4-hats.tar.gz -C / • The package selects the kernel required for the Raspberry Pi model, automatically. If you want to check for the kernel packages released by 4D systems, proceed to the Latest Kernel Versions section. 9. Reboot the Raspberry Pi by running the command sudo reboot now 10. The desktop should begin to show on the 4DPi once the Raspberry Pi has booted. 11. Doing an apt-get upgrade after the Kernel Pack has been installed, will disable the 4DPi and its modifications, as the modules and Kernel would be updated in this process. To reenable, be sure to download the latest Kernel Pack (check this datasheet again if there has been an updated version) and perform the same steps to get up and running again. Results may vary, and it's always advisable to apply the 4DPi Kernel Pack to a fresh image, but this is not always possible. Warning An upgrade should only be done if the latest RPi OS kernel is supported by the latest 4D kernel pack. Otherwise, installing the 4D kernel pack will downgrade the kernel and problems may occur. 12. ADVANCED USERS: If you need to make custom modifications to your Kernel, and want the 4DPi to function, you will need to build the Kernel from the source, and include the 4DPi files in the process. The link to our source is on our website, along with the steps required to add in the 4DPi files so this can be enabled in menuconfig while building the Kernel. Note • It is advisable to use the RPi OS release with a matching kernel version as one of the latest 4DPi packages that you plan to use. If support for a newer version is not yet available, please raise a ticket for assistance. • RPi OS based on Debian Bullseye is not fully compatible with our kernel release. Please use the latest Legacy version which is based on Debian Buster instead. 4D Systems DATASHEET Page 9 of 28 4DPi-32-II Calibrating the Touch Screen 4.3. Calibrating the Touch Screen Each 4DPi which is shipped from the 4D Systems factory is slightly different, in the sense that each of the touch screens has a slightly different calibration. To get the best from your 4DPi, you will need to calibrate the display, so it is as accurate as possible. To calibrate the touch screen, the xinput_calibrator is required, and the following steps should be carried out. Make sure the Desktop is not running before you start, quit the desktop if it is and return to the terminal prompt. Note Only resistive touch display modules could be calibrated. 1. Install xinput_calibrator (if not installed by default) by running this command in the terminal. sudo apt-get install xinput-calibrator 2. Install the event device input driver: sudo apt-get install xserver-xorg-input-evdev 3. Rename 10-evdev.conf file to 45-evdev.conf. sudo mv /usr/share/X11/xorg.conf.d/10-evdev.conf /usr/share/X11/xorg.conf.d/45-evdev.conf 4. Check if evdev.conf has a higher number than libinput.conf. ls /usr/share/X11/xorg.conf.d/ • The user should get something like this: 10-quirks.conf 40-libinput.conf 45-evdev.conf 99-fbturbo.conf 5. Perform a reboot sudo reboot now 4D Systems DATASHEET Page 10 of 28 4DPi-32-II Change the Display Orientation 6. Reconnect to SSH and run xinput calibrator. DISPLAY=:0.0 xinput_calibrator • Perform the calibration and copy results. The result should be something like this: Section "InputClass" Identifier "calibration" MatchProduct "AR1020 Touchscreen" Option "Calibration" "98 4001 175 3840" Option "SwapAxes" "0" EndSection 7. You may test the changes after xinput calibrator ends. To make the changes permanent, paste the results to /etc/X11/xorg.conf.d/99-calibration.conf . sudo nano /etc/X11/xorg.conf.d/99-calibration.conf 8. Save the file and perform a reboot sudo reboot now 9. The Display should now be calibrated. 4.4. Change the Display Orientation To change the display orientation, simply edit the /boot/cmdline.txt file Add the parameter below after the console parts in the parameter list: 4d_hats.rotate = 90 And change this to have the value of 0, 90, 180 or 270. It should look something like this: console=serial0,115200 console=tty1 4d_hats.rotate=90 root= (etc etc) Save the file and restart your Raspberry Pi. The touch screen will automatically remap the alignment thanks to the custom kernel. After changing the Display Orientation, you need to calibrate again the screen. 4D Systems DATASHEET Page 11 of 28 4DPi-32-II SPI Frequency and Compression 4.5. SPI Frequency and Compression The 4DPi can be adjusted to work with a range of SPI Frequencies and levels of compression, depending on the requirements of the product/project. Increasing the frequency can result in a higher Frame Rate (FPS), however, will use more power and processor time. Increasing the level of compression can also result in a higher FPS but may cause the display to corrupt. By default, an SPI Frequency of 48Mhz is used, with a Compression level of 7. The following parameters are the defaults in the /boot/cmdline.txt file and can be edited to adjust the Frequency and Compression level. 4d_hats.sclk=48000000 4d_hats.compress=7 Setting compress to 1 will enable the kernel to control the level of compression based on the frequency selected. This however is not guaranteed to have a good result and may require manually setting the compression level of corruption on the display is experienced. If corruption or display anomalies occur at any given compression level, try to lower it by 1 value and check if this has improved. Note Changing the frequency and compression requires a restart of the Raspberry Pi. 4D Systems DATASHEET Page 12 of 28 4DPi-32-II Backlight Control 4.6. Backlight Control The backlight is controllable in two possible ways. One is using simple on/off control, which is done by sending a GPIO command to the onboard processor, which then turns the backlight on and off. The other is using a DMA-PWM output from the Raspberry PI and controlling the backlight brightness. The control of the backlight is selected using the Jumper J1, selecting ON/OFF or DMA control. For the simple ON/OFF control GPIO18 is used. The backlight brightness can be controlled from the terminal or a bash script. Executing the following command will control the backlight. • To turn the backlight OFF: sudo sh -c 'echo 0 > /sys/class/backlight/4d-hats/brightness' • To turn the backlight ON: sudo sh -c 'echo 1 > /sys/class/backlight/4d-hats/brightness' • To control the backlight using DMA-PWM, ensure that the Jumper J1 is on PWM. The following command can be used to set the backlight from 0 to 100%. sudo sh -c 'echo 31 > /sys/class/backlight/4d-hats/brightness' The above will set the backlight to 100%. Simply change the 'echo 31' to anything from 0 to 31. 4D Systems DATASHEET Page 13 of 28 4DPi-32-II Parameters Listing 4.7. Parameters Listing The following is a list of all the custom parameters used by the 4DPi. rotate: Screen rotation 0/90/180/270 (int) compress: SPI compression 0/1/2/3/4/5/6/7 (int) sclk: SPI clock frequency (long) Valid SPI Frequency values (4d-hats.sclk): Values can be almost anything. This has been tested up to 64Mhz. Common values would include 64000000 (64MHz), 48000000 (Default), 32000000, 24000000 etc. Valid Compression values (4d-hats.compress): 0 (compression off) 1 (compression on, auto set based on sclk value) 2 (lowest), 3, 4, 5, 6, 7 (highest compression) These parameters can be set or read from the /boot/cmdline.txt file, and they can be read from the / sys/module/4d_hats/parameters/ directory. For example: cat /sys/module/4d_hats/parameters/rotate Will display the current rotation saved. 4.8. HDMI or 4DPi Output To switch the X Windows output being displayed on 4DPi or HDMI output, X can be launched using either of the following commands: startx -- -layout TFT startx -- -layout HDMI Alternatively, these commands do the same thing: FRAMEBUFFER=/dev/fb1 startx startx 4D Systems DATASHEET Page 14 of 28 4DPi-32-II DPI Adjustment 4.9. DPI Adjustment It is possible to change the DPI output of the 4DPi in the same way as other LXDE-based systems. • Login as pi and open terminal • Check the current DPI settings by running this command: xrdb -query -all • The current dpi is listed next to the Xft.dpi listing. • You can change the DPI by doing this. • Edit the following file, and then merge it: nano ~/.Xresources • Add this line to the file: Xft.dpi: 75 . • This will set the DPI to 75. • Save and exit the file. • Merge it so the value gets used, by doing the following: xrdb -merge ~/.Xresources • You can now check the DPI settings. xrdb -query -all • Reboot the Pi, and your changes should take effect. Changing the DPI can make the screen blurry, so take care when adjusting these values. If you get to a point where it is unreadable, SSH into your Pi and change the value back to something reasonable. Ideally, DPI is set based on your resolution, however, for small-resolution displays, it can be desirable to make the DPI smaller so you can fit more on the screen. 4D Systems DATASHEET Page 15 of 28 4DPi-32-II Display Module Part Numbers 5. Display Module Part Numbers The following is a breakdown of the part numbers and what they mean. Example: • 4DPi-32-II 4DPi - Display Family 32 - Display size (3.2") II - Hardware Revision 2.0 and higher 6. Latest Kernel Versions Here is the list of the kernel patches released by 4D systems. Latest releases: • gen4-hats_5-10-103.tar.gz • gen4-hats_5-15-32_32bit.tar.gz (refer to the 2nd point from the note below) Previous releases: • gen4-hats_5-10-76-4DPi.tar.gz • gen4-hats_4-19-57-v7l+_v1.0.tar.gz • gen4-hats_5-10-63.tar.gz • gen4-hats_4-14-34_v1.1.tar.gz • gen4-hats_5-4-68.tar.gz • gen4-hats_4-9-80_v1.1.tar.gz • gen4-hats_4-9-59_v1.2.tar.gz Note 1. It is highly advisable to use a Raspberry Pi OS release with matching kernel version (first 2 numbers and 3rd number need to be less than or equal) as the Kernel Pack you decide to use. Please refer to step 1 under the Software Download/Installation section regarding current recommendations. For example, if your OS uses Kernel 5.4.60, then applying our 5.4.68 Kernel Pack is a good match. Example 2, If your OS uses 5.4.79, or 5.5.10, then applying the 5.4.68 Kernel Pack likely would not be the best idea as it would be a downgrade, and some things may not function correctly. 2. This kernel package is versions higher than the recommended latest Buster (legacy) version release. This was built to be able to update the Buster version to a matching kernel version of the Bullseye release. To match the kernel, you can use the command: sudo rpi-update Git hash must be the commit in the Raspberry Pi Firmware Files repository with the same kernel version as the 4DPi package. 3. Some older kernel releases may be available upon request. Please contact 4D Systems Support Team for more information. 4D Systems DATASHEET Page 16 of 28 4DPi-32-II Mechanical Details 7. Mechanical Details 4D Systems DATASHEET Page 17 of 28 4DPi-32-II Schematic Diagram 8. Schematic Diagram 4D Systems DATASHEET Page 18 of 28 4DPi-32-II Specifications 9. Specifications Absolute Maximum Ratings Operating ambient temperature -15°C to +65°C Storage temperature -30°C to +70°C Note Stresses above those listed here may cause permanent damage to the device. This is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the recommended operation listings of this specification is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability. Recommended Operating Conditions Parameter Conditions Min Typ Max Units Supply Voltage (+3.3V) Stable external supply required 3.0 3.3 4.0 V Supply Voltage (+5V) Stable external supply required 4.5 5.0 5.5 V -10 -- +60 °C Operating Temperature Global Characteristics Based on Operating Conditions Parameter Conditions Min Typ Max Units Supply Current (ICC) 3.3V Supply -- 100 -- mA Backlight Current (ICC) 5V Supply -- 150 -- mA Display Endurance Hours of operation, measured to when the display is 50% original brightness -- 20000 -- H PERFORMANCE Parameter Conditions Frame Rate (FPS) Video Playback, Full Screen, 320x240. A higher FPS can be achieved if the display outputs lots of blocks of the same colour. See the SPI Frequency and Compression section 4D Systems DATASHEET Min Typ Max Units -- 25 -- FPS Page 19 of 28 4DPi-32-II Specifications LCD DISPLAY INFORMATION Parameter Conditions Specification Display Type TFT Transmissive LCD Display Sizes 3.2" Diagonal Display Resolution 240 x 320 (Portrait View) Display Brightness 5V Supply, gen4-uLCD-32D 200 cd/m2 (typical) 5V Supply, gen4-uLCD-32D-CLB 194 cd/m2 (typical) 5V Supply, gen4-uLCD-32DT 160 cd/m2 (typical) 5V Supply,gen4-uLCD-32DCTCLB 190 cd/m2 (typical) Display Contrast Ratio Typical 500:1 Display Viewing Angles Above Centre 35 Degrees Below Centre 55 Degrees Left of Centre 55 Degrees Right of Centre 55 Degrees Display Viewing Direction Display Backlighting 6 O'clock Display (Optimal viewing is from below when in Portrait mode) White LED Backlighting 1x6 Parallel LED's Pixel Pitch Pixel Density 0.2025 x 0.2025 (Square pixels) Number of pixels in 1 row in 25.44 mm 127 DPI/PPI Ordering Information Order Code: 4DPi-32-II Packaging: Module sealed in a 4D Systems box 4D Systems DATASHEET Page 20 of 28 4DPi-32-II Appendix 1 - Code Examples - Push Buttons 10. Appendix 1 - Code Examples - Push Buttons 10.1. Example for communicating to Push Buttons, for C language // test program to read state of buttons on 4D Systems 4DPi displays #include #include #include #include #include #include #define LCD4DPI_GET_KEYS _IOR('K', 1, unsigned char *) void print_keys(int fd) { unsigned char keys; if (ioctl(fd, LCD4DPI_GET_KEYS, &keys) == -1) { perror("_apps ioctl get"); } else { printf("Keys : %2x\n", keys); } } int main(int argc, char *argv[]) { char *file_name = "/dev/fb1"; int fd; fd = open(file_name, O_RDWR); if (fd == -1) { perror("_apps open"); return 2; } print_keys(fd); printf("Ioctl Number: (dec)%d (hex)%x\n", LCD4DPI_GET_KEYS, LCD4DPI_GET_KEYS); close (fd); return 0; } 4D Systems DATASHEET Page 21 of 28 4DPi-32-II Example for communicating to Push Buttons, for Python language 10.2. Example for communicating to Push Buttons, for Python language #!/usr/bin/python import array, fcntl from time import sleep # test program to read state of buttons on 4D Systems 4DPi displays # LCD4DPI_GET_KEYS = -2147202303 _IOC_NRBITS = 8 _IOC_TYPEBITS = 8 _IOC_SIZEBITS = 14 _IOC_DIRBITS = 2 _IOC_DIRMASK = (1