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.