Testing the NXT and EV3 programs (continued)

In an earlier article, I mentioned that I wrote a small test program to send commands to a NXT or EV3 program for testing purposes. I have updated this application with the possibility to send and retrieve data over a WiFi connection. Next, you must enter the name of the Brick name to connect to. Error handling is not implemented. For example, if you switch off the NXT or EV3 while the connection is open, the application crashes. That is the reason that I don’t share this application (yet, don’t know if anyone would be interested).

Sending data over WiFi between our PC application and the EV3 (part 3)

In the previous post, I wrote that I didn’t manage to get the Direct Commands working that open and read a mailbox. And that I managed to get the workaround working to send data from the EV3 to the PC application. In this part I will tell you more about the other route that I found.

 

Sending data over WiFi between our PC application and the EV3 (part 2)

As mentioned in the first part of this article, it is possible to send data from the EV3 to the PC application. In this part, I describe how I try to learn the syntax of Direct Command programming.

Sending data over WiFi between our PC application and the EV3 (part 1)

In our project, we use 4 NXT and 5 EV3 bricks. Two of the EV3’s will be connected in daisy chain mode, so we need a grand total of eight connections to the PC application. In our version of 2013, we noticed that more Bluetooth connections results in less reliability. Because of that, our hardware architecture is now based on the NXT bricks to connect to the PC via Bluetooth and the EV3 bricks via WiFi. As mentioned in the previous article, the communication will be done by sending messages back and forth using the mailbox mechanism. By this means, we can create intelligent ‘hardware pieces’, that can handle complex instructions. For example, by sending the string “Uncouple” to a train, the responsible NXT brick will independently handle this instruction and controls the needed actions to uncouple the wagon from the train. The string is read by the Read Message Block, both available in the NXT and EV3 programming environment.

The PC application is responsible for connecting the various hardware parts (delivery station, PUI receiver, crane, etc) and the overall intelligence between these parts. This architecture makes it easy to test the several parts (see also the previous article about the test program) independently and gives more flexibility.

The Bluetooth communication was already implemented both for the NXT and the EV3. All we need is an extension that the EV3 can also communicate over the WiFi connection. That doesn’t sound to difficult. In this article you can read about the ugly truth.

Testing the NXT and EV3 programs

The PC application will connect to the NXT and EV3 bricks by Bluetooth (for the EV3, we are investigating if we can write a block for sending messages over a WiFi connection, but that isn’t easy).

EV3 has WiFi around the corner

Our final track layout will consist of four NXT bricks and four EV3 bricks. If we would connect all the bricks using Bluetooth, we expect the connections to be unreliable. To prevent this problem from happening, we bought the recommended Netgear dongles (about 15 euro per dongle) to connect the four EV3 bricks  using WiFi.

A major issue that arises with the WiFi dongle is when connected to the EV3 Brick, the dongle sticks out from the side of the EV3 brick, getting in the way of everything. Allowing it to be easily knocked out from the EV3 Brick’s USB Socket. Therefor, I used an USB ‘around the corner’ adapter:

You would expect: plug in the USB adapter, plug in the dongle, setup the EV3 software and ready. No… it took me about an hour to get the dongle working. I found out that the USB adapter was the problem. The adapter connecters are too short to function properly if you insert the dongle completely. If you insert the dongle leaving ~2 mm of space, then it works fine. So, I will have to look for other adapters 😦

But when it works, it is a relieve to have the USB cable not lying around anymore around my table. I can recommend this feature.