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mindstorms:nxt_prolog_api [2008/04/21 11:43] gjn |
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| These areas are much more accessible with the use of a declarative programming solutions, compared to classic, low-level imperative languages. | These areas are much more accessible with the use of a declarative programming solutions, compared to classic, low-level imperative languages. | ||
| - | The paper presents research developed within the //[[hekate:HeKatE]]// project [[http://hekate.ia.agh.du.pl]] aimed at providing a high-level rule-based programming solution for Mindstorms NXT, based on the Prolog language API for the NXT platform. | + | The paper presents research developed within the //[[hekate:start|HeKatE]]// project [[http://hekate.ia.agh.du.pl]] aimed at providing a high-level rule-based programming solution for Mindstorms NXT, based on the Prolog language API for the NXT platform. |
| + | |||
| ===== Design ===== | ===== Design ===== | ||
| + | Basing on the review of existing solutions presented above, the requirements of a new Prolog API for NXT has been formulated. | ||
| + | The main requirements are: | ||
| + | * support for all functions of the standard NXT components, that is sensors and motors, | ||
| + | * crossplatform solution, for both Windows and GNU/Linux environments, | ||
| + | * reuse some of the available solutions, and provide compatibility where possible, | ||
| + | * ultimately integrate with the higher XTT layer. | ||
| + | |||
| + | The whole platform based on this new Prolog API is planned as presented in the figure below. | ||
| + | In the figure the highest visual rule-based logic design with XTT is also included. | ||
| + | The focus of this paper is the design and prototype of the Prolog API layer, indicated in the figure by the dotted line. | ||
| + | |||
| + | In order to reuse and support some of the existing solutions, as well as provide implementation flexibility, it's been decided to provide in the first stage a Prolog library, with the following features: | ||
| + | it is executed on a PC, controlling an NXT-based robot, | ||
| + | the control is performed with the use of the Bluetooth or USB cable connection, | ||
| + | the low-level communication is provided by some well-tested existing communications modules, | ||
| + | at the functional level the API is coherent with other available solutions. | ||
| + | |||
| + | {{:mindstorms:prlognxtapi-design.png|Prolog NXT API Design}} | ||
| + | |||
| + | Considering the requirements the following API architecture has been designed. | ||
| + | It is composed of three main layers as observed in the figure above. | ||
| + | * //communication layer// providing the low-level communication with the robot, | ||
| + | * //sensomotoric layer// allowing the exchange information with sensors and motors, | ||
| + | * //behavioral layer// providing a higher-level functions, e.g. drive. | ||
| + | |||
| + | The behavioral layer exposes to the programmer some high level functions and services. | ||
| + | It provides abstract robot control functions, such as //go//, or //turn//. | ||
| + | Ultimately a full navigation support for different robots is to be provided. | ||
| + | (However, different robot configurations require different control logic) | ||
| + | |||
| + | The sensomotoric layer controls the components of the Mindstorms NXT set motors, all the sensors, as well as Brick functions. | ||
| + | This layer can be used to directly read the sensors, as well as program the motors. | ||
| + | This is a layer, that can be used by a programmer to enhance high-level behavioral functions. | ||
| + | |||
| + | The goal of the communication layer is to execute the actions of the sensomotoric layer and communicate with the NXT Brick. | ||
| + | Currently in this layer several modules are present, providing different means of communication: | ||
| + | * a pure Prolog module, using a serial port communication, and the NXT protocol commands, | ||
| + | * a hybrid solution based on the Java-based iCommand library, | ||
| + | * a hybrid socket-based solution, using the NXT++ library, that communicates with the robot. | ||
| + | All of these actually wrap the //Mindstorms NXT Communication Protocol//. | ||
| + | |||
| + | The first solution is the most straight forward one. | ||
| + | In this case standard ISO Prolog stream predicates can be used to control the serial port. | ||
| + | Prolog terms that wrap the NXT protocol have to be provided. | ||
| + | In the second case the Prolog communication module is integrated with iCommand with the use of the SWI Java to Prolog interface called JPL. | ||
| + | Prolog calls are mapped to the iCommand methods. | ||
| + | In the third case, a simple server written in C++ exposes NXT communication with a TCP socket. | ||
| + | The Prolog communication module connects to the server and controls the robot through a TCP connection. | ||
| + | This opens up a possibility of a //remote// control, where the controlling logic is run on another machine, or even machines. | ||
| + | |||
| + | Besides some basic send/receive functions the library has to provide certain services. | ||
| + | These are event and time-based callback. | ||
| + | For example, it should be possible to instruct the robot to e.g. "drive till you hit/approach an obstacle, then make a sound, wait for a response for some time, if you don't get one, turn and drive on". | ||
| + | So the library has to provide //timers// that trigger some callbacks, as well as //event-driven// callbacks. | ||
| + | This requires //parallel// execution of certain threads. | ||
| + | |||
| ===== Implementation ===== | ===== Implementation ===== | ||
| + | For the implementation progress see working pages (so far in polish): | ||
| + | * //communication layer// see [[pl:miw:miw08_mindstormscontrolj|iCommand]], [[pl:miw:miw08_mindstormscontrolc|TCP]], and [[pl:miw:miw08_mindstormscontrols|serial versions]]. | ||
| + | * //sensomotoric layer// see the [[pl:miw:miw08_mindstormsapi|main page]]. | ||
| + | * //behavioral layer// see [[pl:miw:miw08_mindstormsapi|the main page]]. | ||
| + | |||
| + | The [[pl:miw:miw08_mindstormsapi|main API]] page is here. | ||
| ===== Examples ===== | ===== Examples ===== | ||
| + | See [[pl:miw:miw08_mindstormsdesign|the following project]]. | ||
| + | ===== Download ===== | ||
| + | A complete downloadable version of the API will be available soon. | ||
| + | The API will be licensed on the GNU GPL v3. | ||
| + | See the main page of the API for a [[/pl:miw:miw08_mindstormsapi#section12|development version]]. | ||
| + | ===== Papers ===== | ||
| + | A first paper describing the design and the implementation of the API {{:mindstorms:prolognxtapi-draft.pdf|is here}}. | ||
