Gil worked hard on the project even before it started (see “Gil’s electronics lab”). To agree to do the Euro RPi-Rover project dad had him learning electronics, assembling circuits and programming in Python for quite some weeks, and that was even before dad said yes to this project.
We wanted to design and build a rover similar to NASA’s Sojourner, a rover that traveled and explored Mars for the first time back in the nineties, way before Gil and I were born. Before that the only information known about Mars was collected from orbit. Sojourner got humanity on the ground, and it was like walking around on Mars. The scientists in NASA’s command centre would send commands and the little rover would execute them, far away, on a distant planet. Some time after the command was sent, data would arrive and they would get back photos and groundbreaking pieces of data.
The basic idea for the rover was decided. We would have a system with two elements: a command centre and a rover. The commands would come from the command centre and reach the rover by radio. The rover would answer using data from its multiple sensors, including a camera.
With this basic design, we started selecting a chassis and sensors. We googled for components and thought about how they could be connected simultaneously to the Raspberry Pi that would be the brain of the rover.
In this phase of the project, which we called the design phase, we created a list with all the different alternatives available for each sensor. We listed different distance measuring devices, like sonars and infrared rangers, different radios, GPS antennas, etc. We started adding to the list, and when we had enough alternatives to choose from, we proceeded to eliminate the alternatives, until we got down to one choice per module.
We discussed for some time what we would like the rover to be able to do, the difficulty of implementing each module and how it all could be connected. As this went along, we tuned our component list and it became the shopping list for our project!
During this phase we created the first crucial diagram of the project: the system component diagram, or the boxes diagram, as we call it most of the time.
This diagram, depicted below, describes the modules that make up the rover/command centre system, and explains how all the components “talk” to each other, using the various communication buses available on the RPi, namely the UART, SPI and I2C.
Having created the shopping list we had the reference of every component we had to buy, which is different from knowing where to buy them. We had bought the RPi’s starter’s kit and the (rather poor) electronics kit at Amazon UK, but the store’s delivery restrictions meant the stuff we bought could not be delivered to the countries we live in, and had to be delivered in the UK, to our aunt that lives in Cambridge, who then had to mail them again to us in Brussels or Madrid (thanks!). This took forever and meant that our aunt would have to keep going to the post office for us. That was not an option. Other Amazon stores had limited inventories and higher prices (for electronics, at least), so we ended giving up on Amazon altogether for this project. We then started looking for online shops, in Belgium and Spain, and found two that would sell us all the components we needed, that were mostly produced by Pololu and Sparkfun. Later we ended up visiting the physical shop of the Pololu representative in Spain, the Complubot shop, that is a veritable paradise for a robotics enthusiast (recommended, a must see for like minded enthusiasts).
The design phase for our rover lasted until the end of April 2015. By then we had ordered every component needed, collected every data sheet and links to tutorials for every component we would use on the project. We had collected a lot of information and felt confident we could see the project through.
We knew what we were doing. It was time to start planing how to do it.
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Euro RPy-rover 