MAKE-ing with LabVIEW & Raspberry Pi: Part 3 – Raspberry Pi Setup

In Part 3 of this series on using the Raspberry Pi with LabVIEW I will be configuring a Pi 3 B and installing the LINX Toolkit on it. I will also cover some handy hints & tips when setting up the Raspberry Pi.

Introduction

This guide is based on the official set up guide from the Raspberry Pi foundation – found here.

We’ll be setting up the Pi with the latest Raspbian OS package downloaded from the official Pi website and then installing the LabVIEW Run-time.

The Raspberry Pi website offers Raspbian and NOOBS – NOOBS is an easy way to download and try out different OSes for it but it takes up more space on your SD card and may prevent things like configuring it to run headlessly (without a display). I also expect that only Raspbian is supported by the LINX Toolkit.

Prerequisites:

For the initial setup, you’re going to need the following:

• Raspberry Pi: The LINX Toolkit officially supports the Pi 2/3 but I will provide an update or a separate post on other targets such as the new Pi 4 and the Pi Zero W.
• Power Supply: For the Pi 2/3 you need a MicroUSB with an output of at least 2.5A and 3.0A USB-C for the Pi 4.
• >=8GB microSD card: You can use a blank/formatted card or you can buy microSD cards with NOOBS (the Raspberry Pi OS launcher) preinstalled. The SD card will be the disk drive of your Raspberry Pi so will contain the OS and all of your programs/files – it’s worth getting a decent Class 10 SD card or above.
• SD Card Reader: You’ll need to format & install the OS image using another computer with an SD card reader. You might also need a microSD to SD adapter.
• Screen and Keyboard/Mouse: Recommended for the initial setup but read the hints & tips at the bottom of the post to learn how you can set up the Raspberry Pi without these and use SSH and/or VNC to access the Pi remotely.
• Ethernet Cable / WiFi Credentials: To install the LINX Toolkit / LabVIEW Runtime to the Raspberry Pi it will need to be connected to the internet (to download the LabVIEW Runtime) and be on the same network as your LabVIEW 2019 installation (to configure/setup the Raspberry Pi and to deploy code to it).

Of course, you’ll also need your laptop/PC with LabVIEW 2019 and the LINX Toolkit installed – as discussed in Part 2.

How to: Set up a Raspberry Pi for LabVIEW

Hints & Tips

Remote Access – VNC

Once you have done the initial setup of the Pi and it is connected to your network, you might not want to keep a display/mouse/keyboard attached to it. The solution is to enable VNC – it’s the Raspberry Pi equivalent to remote desktop and allows you to view and control the Raspberry Pi remotely.

The first step is to enable the VNC server on the Raspberry Pi using the configuration tool (or via sudo raspi-config). You will then need to install the VNC Viewer which you can download from here.

Once installed, you can enter the hostname/IP address of your Raspberry Pi and then connect using the same username/password as SSH.

Headless Raspberry Pi (no display)

If you don’t have a mouse/keyboard/screen available for the initial setup, you can still setup and configure your Pi over the network.

You can do this by modifying the contents of the ‘boot’ partition of the SD Card on your computer after you have written the Raspbian OS image to it.

WiFi

If you need to use the Pi over WiFi, you can confgure the WiFi credentials by creating a file called wpa_supplicant.conf in the ‘boot’ partition of the SD card. Its contents will then be copied over to the Raspberry Pi when it boots up.

The file needs to look like this:

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
country=«your_ISO-3166-1_two-letter_country_code»

network={
    ssid="«your_SSID»"
    psk="«your_PSK»"
    key_mgmt=WPA-PSK
}

You will need to fill in the country code, SSID and pre-shared key. Ensure that the file has Linux line endings (LF or ‘\n’ instead of CRLF ‘\r\n’).

SSH

Create/copy a file called ‘ssh.txt’ (case-sensitive) onto the ‘boot’ partition of the SSD card. The contents of the file doesn’t matter.

Other Configuration Options

After setting up the WiFi and enabling SSH, you should be able to boot up and then SSH into the Pi. You can try connecting to the default hostname ‘raspberrypi’ or check your router/network settings to find its IP address.

Once you have connected via SSH, you can run sudo raspi-config to access a terminal-based configuration editor which allows you to change all of the settings of the Pi as per the initial setup etc.

Controlling the LabVIEW Run-time

The LabVIEW Run-time runs as a service on the Pi, to start/stop/restart it you can use the following terminal commands:

sudo systemctl [stop|start|restart] labview.service

This can be useful in case you want to ‘reboot’ LabVIEW without restarting the Pi. Note that this will abort any currently running LabVIEW VIs that are running on the target.

Fixing the LINX Toolkit Beta

Update 10/10/2019: The LINX Toolkit has now been updated to Beta 2 on the NI Software Technology Preview – the fixes below are no longer necessary to install the LabVIEW Run-time to the Raspberry Pi. This update potentially breaks the ability to create Real-Time Applications (rtexe) in LabVIEW 2019 – performing a repair on LabVIEW Real-Time from NI Package Manager fixed this for me.

At the time of writing the LINX Toolkit Beta is just a copy of the 2014 version of the Toolkit. It has not been updated or fixed to work with LabVIEW 2019 and newer Pi Targets.

Fortunately I have been able to resolve most of the issues to get the Wizard working to install the Toolkit and launch the examples. This requires changes to some of the VIs to update it for the new LabVIEW Run-time for the Pi.

Most of the VIs are located in C:\Program Files (x86)\National Instruments\LabVIEW 2019\vi.lib\MakerHub\LINX\

Remove LabVIEW 2014 Prompt

Open LMH-Linx.lvlib:System Check.vi and change the string in the case structure from “2014” to “2019”. This will remove the dialog that appears when opening the dialog that you’re using the wrong version of LabVIEW.

Update for 2019 LabVIEW Run-time

Open LMH-LINX.lvlib:Install LV Support.vi and change the package name to ‘lvrt19-schroot’:

Open LMH-LINX.lvlib:Add MakerHub Feed.vi and modify as follows:

Open LMH-LINX.lvlib:Check Target LV Package Version.vi and change the package name to ‘lvrt19-schroot’:

Note: It will still show the latest version as the LV2014 version but it doesn’t affect the installation

Add Raspberry Pi 3 (& 4?) Support

The library detects the target type according to the CPU name retrieved from the cat /proc/cpuinfo command. This is different for the Raspberry Pi 3 (and also the Pi 4 and maybe the Pi Zero etc.).

To add support in the Wizard for new targets we need to do the following:

1. Determine the CPU type on the Raspberry Pi by running cat /proc/cpuinfo in a terminal or via SSH. At the end of the output it will show a line saying something like Hardware: BCM2835. This is the CPU type used by the LINX Toolkit wizard.
2. Open LMH-LINX.lvlib:Get Device Type.vi and add a new entry for the Raspberry Pi you are using (e.g. 3/4):
   
3. To fix the ‘Launch Example’ button in the Wizard, we also need to modify it to use the Raspberry Pi 2 B example files. Open LMH-LINX.lvlib:Script Example Project.vi and modify as follows:
   

If you want to look into the LINX Target Configuration VI, you can open it from the Tools menu and then press ‘Ctrl+.’ to abort the VI. You can then look through its block diagram. Be aware that any changes you make might be overwritten by a new version of the Toolkit. Feel free to leave a comment if you’ve made any other useful changes!

Conclusion

This has been quite a long post, but we’ve now covered everything required to setup a Pi for use with LabVIEW. I’ve also provided fixes for the current Beta version of the LINX Toolkit so you can use the Wizard to install the LabVIEW Run-time and provided some hints & tips for remotely accessing the Raspberry Pi and for setting up the Pi without a mouse/keyboard/screen attached.

In the next post, I’ll go into some details about some of the on-board communications methods on the Raspberry Pi. I will cover network communications and serial ports. Tune in next time!