This has given me the basis to process more sensors in a standard environment in the future and to plan and execute missions for the DiddyBorg.

Software installation on the Raspberry Pi (RPi)

On the RPi, first install pymavlink, the Python version of the MAVLink libraries. The easiest way to do this is with PIP:

pip install pymavlink

Then create a directory, e.g. diddy2QGC, into which you copy the Python modules diddy2QGroundControl.py and ThunderBorg3.py from the Github repository of this project. In this directory you then start the Python script later with:

 python diddy2QGroundControl.py

Software installation on the desktop

Install QGroundControl on your desktop.

Starting the applications

Make sure the RPi and your desktop are on the same network and run QGroundControl (QGC) and the Python script (the order is irrelevant).

The DiddyBorg sends heartbeat messages, which are recognized and answered by QGC. After exchanging a few more messages (please do not be confused by the error messages), the connection is established and you will then find the option to teach in your joystick in the vehicle settings. Please note that diddy2QGroundControl.py in mode 2 uses the roll channel for right/left control and the inverted value of the pitch channel for motor control.

The DiddyBorg sample programs published by the manufacturer PiBorg also include a Python remote control script with joystick, but it uses Bluetooth and therefore has a rather limited range.

The app presented here uses the existing WLAN and UDP as protocol to ensure sufficient agility of the remote control. For safety reasons, the time-out logic of the ThunderBorg motor controller is activated.

Software installation

The DiddyBorg needs a Python script JoystickRC4DiddyBorg as receiver, which you can find on github.com. In addition to the receiver program, you will also find a version of the ThunderBorg – Library for Python 3.x in the repository (the sample programs for the DiddyBorg are still based on Python 2.x).

The easiest way is to copy the two files additionally into the directory with the examples – then the script should work without further adjustments of path names.

On the PC side, install the Windows app JoystickRC4DiddyBorg of the same name, which you can get for free from the Microsoft App Store.

Operation

First start the Python script on the DiddyBorg. If you have a screen connected, then the program will log in and indicate that it is waiting for a client.

When you start the PC app, it will automatically search for a DiddyBorg with an active and compatible receiver on the local WLAN (to which both the DiddyBorg and the PC being used must be connected). If no connection can be established, a corresponding error message is displayed.

After the connection has been successfully established, the channels can be assigned to the various joystick axes and keys. Channels 3 and 4 are used as push buttons and allow for example fast / slow rotation (the function of the push buttons can be traced in the Python script).

The assignment of the channels is saved and restored at the next program start.

In this blog, an even more compact structure is described in which the USB hub, the USB2PPM PiKoder and the multi-protocol module are mechanically combined into one unit, which then only needs to be connected to the smart device and the joystick.

The following steps are required for the implementation:

1. 1. Extend the USB hub cable
   2. Modify USB2PPM PiKoder with USB connector
   3. Realize mechanical rack
   4. Assemble and wire modules

Extend the USB hub cable

The common USB OTG hubs (on the go) usually have a very short connection cable (0.1 – 0.15 m). In practical use, this results in restrictions, since the hub must always be close to the smart device and possibly hangs in the air next to the holder and so a “rigid connection” with the PiKoder is not possible.

The extension of the connection cable is not a problem. It is only to be noted that an OTG connector with the corresponding coding (see picture) is still used as the connector, because otherwise the hub will not be recognized and will not be supplied with voltage.

The easiest way to extend the extension is to solder a piece of USB cable of the desired length to the hub board and attach the existing plug with the short cable end to the other end and fix it with shrink tubing.

Modify USB2PPM PiKoder with USB connector

For the direct connection between the USB hub and the PiKoder, the USB2PPM requires a USB plug (see picture on the right) instead of the normal USB micro socket. So that the connector can be installed, saw the circuit board in order to then be able to push through the fastening straps. In addition, a hole is required in order to be able to wire the connection cables of the plug (see picture below).

Then stick the connector to the circuit board with two-component adhesive and equip the circuit board with the remaining components (see pictures below). Note: In the further course of the project I replaced the three-pin header with a Molex connector.

Finally connect the pins of the USB connector with the corresponding PiKoder pins; a thin, insulated wire is used for this. The following pictures show the schematic connection and then you can see the actual wiring on the underside of the circuit board.

Realize mechanical rack

The subrack consists of a simple angled wooden structure. The square base plate with a side length of 85 mm accommodates the hub and the USB2PPM Pikoder. The multi-protocol module is clamped in the vertical fork. To improve the appearance of the cable routing, I drilled a corresponding channel.

Assemble and wire modules

You can see the complete setup in the following pictures. The hub is fixed with double-sided adhesive tape, the USB2PPM PiKoder is plugged in and fixed with screws through the two front mounting holes. It is best to use some washers as spacers so that the circuit board does not bend.

With the micro USB connector, the “compact transmitter” is initially intended for connection to an Android device. With a small adapter, e.g. from Micro USB to USB C plug, the transmitter can of course be easily connected to a Surface Notebook.

The overall structure can therefore be simplified by using a multi-protocol TX module such as the iRangeX iRX4 + instead of the complete remote control transmitter.

The module can – just like the remote control transmitter – be controlled directly via the PPM signal from the USB2PPM – PiKoder. Since the iRangeX already operates with an operating voltage of 5 volts, the power supply is also provided via the USB2PPM PiKoder and no additional battery is required.

Setup

The USB2PPM PiKoder is set up according to the instructions. Even if you have only equipped one cynch socket so far, the three-pin header can be retrofitted without any problems.

The connection between the iRX4 + module is made via a three-wire cable (Vcc, PPM and Gnd) (see picture below left). At one end of the cable there is a three-pin socket for plugging into the corresponding pin header of the USB2PPM, on the other side the five sockets of the module are adapted – you can see the pin assignment that the module expects in the picture on the right.

No further adjustments or changes are required.

And the structure described here can of course also be used in connection with a Windows notebook.

The hardware structure in the title picture is the same as the configuration in the Part 1 Except for the computer, which is replaced by the smart device, and the hub: a USB OTG hub must be used in conjunction with the smart device.

With regard to the preparation of the remote control transmitter, the same considerations for ergonomics apply and it is advisable to expand the remote control with a switch as described in Part 1.

With regard to the app itself, you can choose between the free app Joystick2PPM and a special app for quadrocopters Joystick4UAV (see below); you can find both apps in the Google Play Store.

Joystick2PPM (Android App)

The user interface of the app largely corresponds to the Windows implementation and is intuitive and easy to understand. The joystick controls are on the left and the servo channels are mapped to the right with drop-down boxes.

The joystick and the USB2PPM are automatically recognized after starting the APP. When using the application for the first time, the user must enable access to the corresponding USB interfaces.

Please note that the app currently only supports a limited number of joysticks and other operating devices. The current list of the compatible devices can be found in the Playstore at any time.

Joystick4UAV (Android App)

The Joystick4UAV app is an advanced version of the Joystick2PPM application, which is geared towards the needs of remote control of quadrocopters or other vehicles (UGV) and boats (USV) with a flight controller.

The basic structure of the Joystick4UAV corresponds to the apps already described. The four joystick axes are mapped to the remote control channels 1-4 according to the usual assignment for flight controllers. You can of course adapt this assignment within the four channels according to your preferences. All channels can be inverted by checking the associated box.

The flight mode is coded in channel 5. There are six modes available. The flight mode selection takes place by pushing the joystick buttons 7-12 (see figure below right), where button 7 sets flight mode “1” and button 12 sets flight mode “6”. The selected flight mode is displayed numerically (“1” in the picture above) and the bar corresponds to the transmitted channel value.

The remaining buttons 1-6 (button B1 .. B6 in the upper area) and the hat switch are available for special functions and can be assigned to channels 6-8 as required. If the box belonging to the channel is activated, the button behaves as a switch.

Please note that only the Logitech Extreme 3D Pro joystick is currently supported in the app.

The Ardupilot Mega (APM) and other flight controllers are frequently controlled by a PPM stream rather than the parallel input per channel which I described in part 1 of this blog. The new PiKoder/PPM wRX receiver with its PPM frame output brings this capability to you. The connection between the receiver and the flight controller is reduced to a single 3 strand cable as shown in the featured image.

Description

The PiKoder/PPM wRX receiver will be controlled by the udpRC4UGV App as described in part 2 of this blog.

The feature set of the app has been extended to allow you to freely determine the position of the direction and throttle channel within the PPM frame through the app preferences.

To change the channel setting please select the respective preference and enter the channel number (1 .. 8). E.g. the APM Rover configuration features direction on channel 1 and throttle on channel 3.

Please note that setting the APM’s input mode from parallel to PPM requires a jumper between channel 2 and channel 3 input as shown below.

As already indicated in the previous blog on the topic “Ardupilot Mega Rover with the smartphone remote control“, now, after some further work on the topic, a new Android(TM) app “udpRC4UGV” with rover-specific functions is available. The most important enhancements are the selection of the flight mode and the toggling of channel 7 making a number of APM special functions available.

Description

As outlined in the previous blog a PiKoder/SSC wRX receiver replaces the standard RC receiver in the rover. The smartphone RC uses WLAN for command transmission: the PiKoder does offer an access point (AP) to which the smartphone will connect.

The remote control app offers a variety of user interfaces: from simple key control to a virtual joystick to an accelerometer-based option.

In addition to the general controls for remote control, each user interface also offers the possibility to choose the flight mode. In addition, channel 7 can be triggered via the “CH7” button (for example, in LEARNING mode, the current position is saved as a waypoint).

The app is available free of charge from the Google Play Store. The User Manual can be downloaded from the PiKoder website; it describes not only the program operation in detail, but also the hardware setup.

In the standard setup of the Ardupilot Mega (APM) for Rovers you would deploy a conventional RC for manual control: the RC receiver feeds the input channels of the APM with PWM signals for Rover movement and for executing special functions such as switching flight modes.

If you replace the conventional remote control receiver with a PiKoder receiver – either WLAN- (PiKoder/SSC wRX or Bluetooth -communication (PiKoder/SSC RX), then the Ardupilot can be controlled via an Android based smartphone or tablet using the remote control apps udpRC or respectively btRC.

Setting up the rover

First, the APM is loaded with the Mission Planner with the ROVER configuration; a further adjustment of the parameters was not necessary in my case.

The following image shows the very simple hardware setup.

The PiKoder – channel 1 is connected to the APM input 1 (steering) and the PiKoder – channel 2 to the input 3 (throttle). The standard rover wiring is used at the output side (steering servo on channel 1, ESC with BEC on channel 3). In this configuration, the Ardupilot takes over the power supply of the receiver.

The Ardupilot does not respond to PWM signals that are below or exceeding the typical range of approx. 1,000 – 2,000 µs. Therefore, the minimum and maximum values of the pulse values of the PiKoder/SSC have to be adjusted, as shown in the following figure.

For this purpose, the PiKoder Control Center (PCC) is used as described in the User’s Manual for the PiKoder/SSC wRX.

This completes the set up; the function of the apps is described in the user manuals.