In the two previous articles on model remote control with joystick, a “completely normal” remote control transmitter was used to transmit commands. The control sticks and various switches of the transmitter were not needed because the control itself is done by the joystick.
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 first entry in this series used a notebook to translate the joystick inputs into commands for the USB2PPM. Alternatively, an Android (TM) smart device with a corresponding app can be used for selected joysticks.
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.
I am currently working on the restoration of a Metz MECATRON ‘BABY’ radio remote control. For testing and commissioning the rowing machine, I didn’t want to switch on the entire remote control every time, so I built a simple tester.
This tester reproduces the output of the receiver 191/S – a relay with a switching contact – with a corresponding button. Thus, the function of the rowing machine, which depends on the control panel used, can then be tested.
In my case, the control panel 1 is inserted; the following switch rhythm is realized according to the user manual:
Transmitter key pressed: Rudder left as long as button remains pressed
Press the transmitter button briefly (approx. 0.4 seconds), release briefly (approx. 0.4 seconds) and hold down: Rudder on the right, as long as the button is pressed the second time.
After letting go of the transmitter button, the rudder always goes neutral by itself.
In the setup presented here, of course, the transmitter button corresponds to the button.
The tester can be easily mounted on a laboratory circuit board and the wiring effort is minimal. As can be seen in the picture, I realized the required 7-pin plug for connection with the rowing machine by inserting soldering nails into a 7-pin tube socket.
This article shows how a Spectrum DXe remote control transmitter can be used with the help of a USB2PPM adapter and a notebook to fly a quadcopter with a joystick.
The project includes the following steps:
Preparation of the remote control transmitter
Building of the USB2PPM Adapter
Download the Joystick2PPM program
Settings and commissioning
In addition to the remote control transmitter, PC or notebook with Windows 10, USB2PPM adapter and the joystick, a trainer cable is required to connect the remote control transmitter to the USB2PPM and a USB cable.
Preparation of the remote control transmitter
The spectrum DXe remote control transmitter is controlled by the teacher/student jack on the back of the transmitter. An external PPM signal can be fed into this jack – usually from a second transmitter, the student transmitter. The jack is a 3.5 mm standard jack and the cable connection is made via a corresponding mono-aux cable.
In order for the teacher to be able to take control quickly at any time, the student’s signal is only transmitted as long as the teacher pushes the bind / panic button. This practical implementation of the teacher-student operation naturally makes it difficult to take over the transmitter permanently, since you probably cannot or do not want to manually push the button down while flying.
Therefore, I have installed an additional switch in my Spectrum DXe in order to be able to permanently switch the remote control transmitter to student operation. Although the installation is simple, you should only consider it if you accept the likely loss of the warranty.
Installation of the additional switch for permanent student operation
The housing is opened as described in the manual. In the back half of the transmitter housing there is already a hole at the ideal position, which is covered from the outside by a sticker (see red arrow in the picture).
Expose the hole and insert the additional switch (see details).
The wiring is done in such a way that the Bind/Panik/Trainerbutton is shunted (see picture). For this purpose, a short piece of wire is soldered to the small printed circuit board.
I then attached a small arrow on the outside so that I always know in which mode the transmitter would be currently (see picture).
Building of the USB2PPM Adapter
Of the USB2PPM is implemented according to the assembly instructions, but the last step is omitted (soldering in the three-pole PIN bar for the PPM signal). Instead, a 3.5 mm jack is placed in the experimental field of the printed circuit board (see pictures) to connect to the Spectrum DXe.
With this, all hardware bits and pieces for setting up the remote control are ready.
Download the Joystick2PPM program
The Joystick2PPM program takes over the evaluation of the joystick positions and the conversion into corresponding commands to the USB2PPM. This in turn generates the PPM pulse frame as an input signal for the remote control transmitter.
Now connect the USB2PPM adapter and joystick to your PC. When connected for the first time, Windows 10 will automatically install drivers and associate the adapter with a COM port.
After completing the driver installation, start the Joystick2PPM program. The program automatically connects to the USB2PPM and the first joystick it finds and displays the available axes and switches on the left-hand side of the screen.
Now you can start to configure the channels for your application model-specifically.
For this blog I have chosen a Blade INDUCTRIX quadrocopter as an example, but you can of course also connect other copters.
For configuration, assign the joystick controls to the individual channels of the remote control on the right-hand side (the instructions for the model may contain information on how to assign the channels). If you click on the selection box for a channel, all control elements that have not yet been assigned are displayed and you can make your selection for this channel by clicking on them.
As soon as you have made an assignment, the current value for this control element is transferred to the right-hand side as the channel value. You can see the complete configuration for my application in the following screen dump.
Now turn on your transmitter and make sure that the transmitter is “paired” with the remote control model (trainer switch to “off”). Now, without turning off the remote control transmitter, connect the USB2PPM adapter using the training cable with the remote control transmitter. After turning on the trainer switch, you can remotely control your model with the joystick. If necessary, you can perform the trimming for the individual channels and a possible servo direction reversal on the PC.
In previous blogs related to RC with a web browser I presented solutions which were suited for simple and none time critical applications due to the user interface and the system response time.
The initial concept of a button based user control was relatively slow because the web page had to be re-transmitted and rebuild on the client side after each user interaction.
The improved “joystick”-based interface was already deploying AJAX to improve the system agility. However, in order to initiate a command you would have to touch the screen and to stop the movement you would have to touch the screen at another location which is not very intuitive. You would probably expect a movement to last as long as you touch the screen.
The latest version of httpRC presented here does address both requirements based on a button based UI: a command is executed only as long as you touch it in a very agile way.
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 such as the WLAN receiver PiKoder/SSC wRX, then the Ardupilot can be controlled via a smartphone, for example in the rover configuration. As an user interface, either the Android remote control apps udpRC or picCAR can be used for this application or the browser interfacedescribed in the previous article.
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.
Outlook
The implementation of further configurations and functions has now been done and incorporated into the Android app udpRC4UGV, which is described in the continuation of this blog.
Since both the apps are open source and the receiver protocol is disclosed, you can of course also make your own modifications and extensions.
In this project, a web server is implemented on the ESP8266 – similar to my blog Model Remote Control with Web browser. Using this concept, a browser based (and therefore operating system neutral) radio control could be easily made available. In this project, especially the HTML5 based user interface implementing a joystick caught my attention.
The software is open source and so I was able to change the program for use with a PiKoder/SSC wRX. Additionally, I adapted the code for controlling a ‘normal’ car or boat (one channel for speed, one channel for direction). The customized source code is available in a github repository.
The servo tester presented here is equipped with a PIC controller to provide for very accurate pulse generation (pulse width: 1 ms – 2 ms) especially in comparison with a simpler construction with RC links. For this purpose, the internal oscillator is used, which is specified in the selected range of the supply voltage with an accuracy of 1 %.
Furthermore, the servo tester is characterized by the fact that, in contrast to other simpler digital devices, the supply voltage range is specified form 4.8 V – 6 V. With this, the servo tester can also be connected to the BEC connection of a speed controller. The polarity of the pulse for servo control can be adjusted by hardware (jumper setting).
In addition, the Servo Tester enables the use of servos for other applications, such as for rotating and panning surveillance cameras.
Circuit
The circuit is based on the PIC12F675, which controls the servo tester. The supply voltage of the controller is lowered to 3.3 V by a corresponding controller; this ensures the highest accuracy of the internal oscillator on the one hand and the large supply voltage range of the tester on the other hand.
However, this approach requires a driver transistor Q1, which performs the level adjustment to control the servo. The supply voltage of the servo is directly looped through, so that servos or motor controllers can be tested either with the already existing battery / BEC supply by the speed controller or by means of an additional power supply (in this configuration it must be ensured that no power is provided via the servo plug).
The jumper JP3 determines the polarity of the control pulse for the servo. Please note that the LED is a bi-color LED.
Operation
The operation is simple and intuitive. The servo tester has two different operating modes: the manual mode, in which the servo is controlled by a rotary knob P1 and the neutral position can be adjusted and the exercise mode, in which the servo is continuosly moving between the end points. The change between the two operating modes is carried out by pressing the button S1. The LED will indicate the active mode of the servo tester.
After switching on, the device is in manual mode and the servo position is adjusted by rotation of the potentiometer P1. In the pulse area outside the window of 1.45 ms and 1.55 ms, the LED lights up in green. To move the servo to the neutral position, the color of the LED within the window of 1.45 – 1.55 ms changes to yellow or both colors of the LED light up and when the neutral position of 1.5 ms is reached, red is finally displayed; no button has to be pressed and both hands are free to perform adjustment work if necessary.
The Exercise Mode offers two speeds to choose from. The LED flashes red in this mode and shows which speed was selected via its flashing frequency (0.25 s corresponding to 2 x flashing/second or 15 s (correspondingly once 2 s on, then 2 s off) from final rash to final rash). The speed is switched by turning the potentiometer: if a pulse length greater than 1.5 ms is set, then the Exercise Mode is selected at high speed, otherwise the servo is controlled slowly.
Software Download
The firmware for the servo tester (Release 1.0) is freeware, which can be used without restrictions for private, non-commercial purposes according to the underlying End User License Agreement (EULA).
