IP Display Dongle

IP Display Dongle – Usage & Software

(Click on any image to enlarge)


The IPDisp V1 is a 4-digit 7-segment LED display utilising a “retro” LED of the type found in 1970s calculators. This makes for a cute little display device that can be used to display anything you like that will fit in a 7-segment display. V2 uses a standard 7-segment display which is slightly larger. Both PCBs are the same size: 40 x 32mm (width x height).


You can purchase it here at 4tronix.


It was conceived as a device to help roboteers find the IP address of their robot so that they can connect to it via SSH or VNC for control purposes. Of course you can use a network scanner such as the excellent Fing, but that can become unwieldy in a corporate or educational establishment with a lot of connected devices. This unit is much more fun and can be setup to display the IP address directly on boot up.


IPDisp uses an I2C Port expander chip, the MCP23017, to address all the segments (anodes) as well as the individual common cathode digit drivers. The provided software, in Python, time-multiplexes the digits so that each digit is displayed for only 25% of the time.


Connecting the IP Display Dongle

The pinout is designed to match the I2C expansion socket on every 4tronix robotics controller board: PiRoCon, MicRoCon, Pi2Go and PGX. Simple select the type of header you want to use and solder it on. You may want it to lie flat, stand vertical, lie flat but higher up (extended header), etc. Then, making sure that you have it correct way round, plug it directly into the I2C expansion header. Here we show it plugged vertically into the I2C expansion connector on a MicRoCon controller board.


We also include female headers in the package, so you can plug into a male header, or use male-ended jumper wires to connect to your I2C pins. In fact, apart from the 5V connection, the layout of the pins matches the standard GPIO header on the Raspberry Pi, pins 1, 3, 5 and 7. So plug the header in to the pins as shown below, with the 5V pin hanging off the end. You then have 2 choices:

  1. Use a male-female jumper wire to connect the 5V on the IPDisp to Pin 2 on the GPIO header
  2. Solder across the last 2 pins (5V and “not connected”). This powers the IPDisp off the 3.3V from the Raspberry Pi. Although it “works”, it is not recommended except frr emergencies as it does use too much power for continuous use.

ipd02 Option 1

ipd04Option 2


Running the Software

Make sure that you have the I2C drivers enabled on your SD card. If not, follow this post by Raspi.TV

Download the python sample file and run it using sudo python ipd03.py:
$ cd ~
$ mkdir ipd
$ cd ipd
$ wget http://4tronix.co.uk/ipd/ipd03.py
$ sudo python ipd03.py

This will display the IP address and scroll it across the display a number of times, before quitting. If the Pi is not connected to a network, then it will display 0-0-0-0 and wait until the network is connected before displaying the correct IP address. As the continuous updating of the display is processor intensive, we don’t leave it running permanently.

The current version of the software will exit with an exception if the IPDisp is not connected. We didn’t bother to catch the exception as the information is what we need anyway.

Of course, this is not a lot of use  like this because we must already be connected, or running locally when running the application like this. It is much more useful to get the program to autostart when the Pi boots up. To do that follow the instructions to instigate a startup program when the desktop starts. (you can also put the code in the startup list, but we’ll do it like this for now)

Open LXterminal

$ cd ~    (back to home directory)
$ cd .config
$ mkdir autostart   (not required if it already exists)
$ cd autostart
$ sudo nano ipd.desktop

…and enter the following lines. Note that the Exec line needs to have the correct location for where you have put the program.

[Desktop Entry]
Exec=sudo python /home/pi/ipd/ipd03.py

Exit (ctrl-x) and save (y) then reboot. The IPDisplay will show the IP address of the Pi.



Converting Initio Robot Platform to Stepper Motors

Initio Robot Platform with Stepper Motors

(Click on any image to enlarge)


The Initio robot was designed to be able to use stepper motors as an option instead of the DC motors. It is fairly easy to put the motors in, but slightly trickier for the control of them.


The following instructions are mainly photo based, with only a few comments…

Starting Position



Loosen the inner 2 screws on the inside of one Gearbox



Remove the 2 outer screws to release the gearbox





NB. It is not necessary to remove the DC motor, but I show it here for completeness

Carefully unclip the motor. This probably requires 2 people: 1 to pull the motor out and one to hold back the retaining clips



Unscrew the wheel sensor from the gearbox. Keep the screws as we’ll use them to attach one of the stepper motors.

step07 step08


Slide the switch on top of the gearbox (one above each wheel) to the inside. this allows the wheel to rotate freely without turning the gears. It also means the stepper motor is mechanically disconnected from the DC motor so it is free to rotate.

step09 step10


Fit the stepper motor, ensuring that the shaft lines up with the retaining hole in the gearbox. Use the 2 screws that previously held the wheel sensor for one stepper motor. The other stepper motor will require 2 screws of the same size from the Initio pack of screws

step11 step12 step13


Repeat for all 4 stepper motors and replace the gearboxes, bringing the cables up to the top of the chassis mounting plate

step14 step15


Prepare the ULN2003 boards for connecting 2 stepper motors to each board. If you purchased your stepper motors including boards, then you can remove the JST sockets from one board for each side of the Initio and use that as shown below. Otherwise you will need to purchase the correct JST sockets. We use a single controller board for both stepper motors on one side of the Initio, and solder the extra socket over the pins on the underside of the board as shown in the photos below.



Bend over the pins at 90 degrees (away from the side with the slots in). Then solder to the underside of the board

step17 step18 step19


You can then screw the control boards into any available mounting pillars – one screw per board will keep it in place.



Next step: writing some code…