Changing the Information Delivery Method

After spending large periods of time researching various methods of image and colour recognition in various environments including PureData, Quartz Composer and JavaScript, most of my trials were unsucessful. PureData and Quartz Composer were both unable to recognise the MJPEG stream coming from the Raspberry Pi in order to import it. Even though I found many working examples of JavaScript tracking colours and doing various things once the colour was detected, I could not manage to get it to work with the stream from the Pi either. The following videos demonstrate this.

http://player.vimeo.com/video/48443629

http://anavallasuiza.com/popcorn/

The main issue seemed to be that they are working with a video, and the MJPEG stream outputs images and writes them to the canvas. I found an example that detected a red ball in an image on the JavaScript canvas, however that had specific checks for the size of the ball, and i could not compile the two scripts together without causing the stream to cease being displayed.

I have had to settle for a working but less interesting alternative, which is different to the  other contingency plans that I initially thought up, as it is more reliable.

On the left hand side of the main viewing screen I have created a script that will randomly redirect the user from the iframe with the telemetry .gif inside of it to one of a number of different facts about Mars. The user will then be redirected after a period back to the telemetry. I have also added a flashing warning triangle .gif and alert noise to draw the user’s attention.

warning

The warning .gif which animates for a short period of time when the page loads

Creating the User Interface

The user interface and controls are both web based due to the ease of customisation and wide range of functions that can be achieved via the various web languages such as HTML, JavaScript and PHP.

Main Screen

interfaceFor the main viewing screen I have decided that the central focus should of course be the camera’s video feed. I decided to centre this, and then overlay a clear .png image of the same size in a separate ‘div’ on the page  to create the ‘artificial horizon’ overlay on the camera. I found however that when the screen resolution is changed, it moved the png from the correct position. This is mainly an issue when moving it from the computer that I am developing it on to the projector or other monitor that might be of a different resolution. I solved this by leaving one page with the video feed and png overlay, and creating a new page with an iframe in the centre of it.

Similarly, I decided that to make the main page as simple and flexible as possible that everything should be in iframes, so the code for the main page only consists of three iframes, each aligned to a spate part of the page.

For the telemetry and satellite displays I decided that they should occasionally change to reflect new data coming in. I looked into JavaScript’s random function for this, and I decided that it would require a too high of a refresh rate to achieve the effect that I wanted. I therefore opted to create looping .gif images instead. For the telemetry, I decided to use two separate .gifs on two separate pages, and have a JavaScript function that occasionally refreshes the page to the other one.

Control Interface

controls

My Initial draft of the control interface.

For the first draft of the controls I have stuck to the triangular design for the buttons, and I have redesigned the .gif on the ‘waiting’ page that is called when using some of the controls so that it incorporates the font and feel that is used on the main viewer page.

Additionally, it only runs through once before returning to the previous page as opposed to the old gif that was on a loop.

Note that the wheel direction triangles change colour depending on what the current direction is.

Original .gif

Original .gif

 

For the final design I want to smarten up the interface and make the buttons resemble what they are more clearly. I want to keep the triangle theme, but I also would like to make it feel more like a professional user interface, whilst retaining some of the brightness to engage younger users.

Working with Electronics: Controlling the Electronic Speed Controller via the Web

The Electronic Speed Controller (ESC) can be controlled in the same way as the servo using the Raspberry Pi’s GPIO pins. The biggest difference is that theCapture pulse widths to control it are different.

To find out what pulses made it do what I decided that it would be easier to set the duty cycle to 10o and then to change the pulse widths based on this. I discovered that then at a pulse width of 15 the ESC made the motor go forwards, and after much trial and error, that a pulse width of 13 made it go backwards.

Control via PHP

PHP runs python scripts on page load, so I needed to have the control buttons link to a page with the python script called on it. I could do this in a similar way to how I did with the servo control and have several different pages that look the same but with different scripts called when they load, however this would leave me with over 10 different pages, and this seems like a lot.

I therefore decided that I would load a page that calls the ‘forwards’ or ‘backwards’ script, then goes back to the page the user was just on. To do this I needed some JavaScript.

<script type=”text/javascript”>

window.setTimeout(‘history.back();’, 1000); // waits a specified number of seconds before going back

</script>

This simple bit of script went into the <head> of my document. By changing the value ‘1000’ to another number you can change the time period that the page waits before going back. I then decided to add a simple message to the page that told the user that their previous command was currently in progress. I decided a .gif would make the page more interesting.