Intel Do-It-Yourself Challenge Maestro Pololu card + Bluetooth

Transcription

1 Intel Do-It-Yourself Challenge Maestro Pololu card + Bluetooth Cédric Andreolli paul.guermonprez@intel.com Intel Software

2 Agenda

3 Agenda Introduction How does it work? Sending commands via bluetooth Adapting the project Conclusion

4 Introduction

5 Introduction We still want to use the micro Maestro card but we want to avoid using a USB cable. This new approach offers many advantages : - The USB cable can't be unplugged with unexpected vibrations - The robot/drone will be lighter - The Android phone will not have to be USB host

6 Introduction In the previous course, we learned how to build:

7 Introduction In this course, we will learn how to build:

8 How does it work?

9 How does it work? We must use a bluetooth card. You can use cheap cards such as the JY-MCU Bluetooth Wireless Serial Port Module (=~ 8$). This card must be plugged with the micro maestro.

10 How does it work? The Intel phone send the commands via bluetooth, the bluetooth card receives those commands and send them to the micro maestro card via serial port.

11 Sending commands via bluetooth

12 Sending commands via bluetooth The android application will have to deal with bluetooth communications. Bluetooth communications use sockets. All the documentation can be found : vity/bluetooth.html

13 Sending commands via bluetooth The Android interface: BluetoothAdapter: Allows to get a reference on the bluetooth devices. BluetoothDevice: Represents a device with bluetooth activated. BluetoothSocket: A socket that allows to send data on a device. We will only need those interfaces!

14 Sending commands via bluetooth Step 1: Retrieve the bluetooth adapter Step 2: Get the list of bounded devices Step 3: Iterates over those devices

15 Sending commands via bluetooth Step 4: Connect to the device The UUID can be found in the documentation

16 Sending commands via bluetooth Once you have the output stream, you are ready to use the socket. Sending a message via bluetooth is straight forward. Android provides high level interfaces to do it!

17 Adapting the project

18 Adapting the project The previous project worked with a USB connection. It could be interesting to keep this possibility. The best way is to create an interface! Let's call this interface IMessageSender.

19 Adapting the project The IMessageSender interface provides a set of usefull methods that we will use to control a drone. This interface must be implemented for the USB and for the bluetooth.

20 Adapting the project The bluetooth implementation is straight forward has we saw previously. We just need to add few overhead to check that variables are correctly initialized. The following slide shows the constructor of the class BluetoothMessageSender that implements IMessageSender.

21 Adapting the project

22 Adapting the project Best practices! Create a constant instead of using directly the UUID in the function call. Log the errors and display them to let you know if something goes wrong.

23 Adapting the project How to send a command via bluetooth? We've seen that the bluetooth interface allows us to communicate via sockets. We only need to write the appropriate set of bytes on the socket. The commands can be found in the maestro documentation.

24 Adapting the project Here is a screenshot of the Pololu official documentation.

25 Adapting the project The Pololu card can understand different protocols. Our following examples will use the MINI SSC protocol. This protocol requires short messages. The following example shows how to reset the position of a servo motor to it's neutral point (127 because the range of the servo goes from 0 to 255).

26 Adapting the project We can now implement the method : The parameter position is a value between 0 and 100. We need to rescale this value between 0 and 255 :

27 Adapting the project The full method :

28 Adapting the project Implement the interface for USB We will not explain the USB implementation in details here (see previous course). Use the constructor to initialize the USB connection. Then re-implement each function of the IMessageSender interface.

29 Conclusion

30 Conclusion Through the 2 previous set of slides, we've seen how to develop a server application that controls the pololu card via bluetooth or via USB. Those courses are also a good illustration of the Android course. You should be able to program some nice Android applications right now!

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