Logo for NXT

Welcome to Logo for NXT

Eurologo2007 Workshop

This page contains information about the project of programming NXT in Logo language.

The project is under intensive development, and there are no releases yet. However, the projet is open-source and the latest development version is available in the CVS.

Features

• Implemented in Imagine and Next Byte Codes (NBC)
• Three levels of use:

1. Interactive Imagine project with direct GUI controls that allow interfacing with NXT robot over Bluetooth
2. Loadable imagine library (nxt.imt) that contains set of procedures for direct control of NXT robot over Bluetooth from your Imagine projects
3. Interpreter of Logo running on the NXT that can run logo programs (with restricted syntax), which can communicate with Imagine projects and control the robots motors and sensors.

Motor & Sensor procedures

(motor m cmd arg)

  where m is the number of motor(s) as in NBC:
   0 - motor A
   1 - motor B
   2 - motor C 
   3 - motors AB
   4 - motors AC
   5 - motors BC
   6 - motors ABC
   
  and cmd is one of (with the corresponding argument, similar to NBC):  
    onfwd       power
    onrev       power   
    off         (ignored)
    float       (ignored) 
    fwdr        [power regmode]
    revr        [power regmode]
    fwds        [power turnpct]
    revs        [power turnpct]
    onrot       [power angle]
    rst         kind  (1-4)     

(readmotor m cmd)

  where cmd is one of:
    rotations
    tacho
    blocktacho

(sensor N)

(setsensor N type)

   where type is number according to NBC:
     0 - raw
     1 - switch
     2 - temperature
     3 - refl
     4 - angle
     5 - light active
     6 - light inactive
     7 - sound db
     8 - sound dba
     9 - custom
     10 - lowspeed
     11 - lowspeed with 9V
     12 - high speed
   add the following constants for adjusting the output:
     32 - boolean output (0/1)
     64 - transition count
     96 - period counter
     128 - percentage (0-1023 value normalized to 0-100)
     160 - temperature in C
     192 - temperature in F
     224 - angle steps
     31 - slope mask
     224 - mode mask

Supported primitives

NXT Logo supports the following primitive procedures and operations:

1. Arithmetic: add, sub, mul, div, mod, neg
2. Logic: and, or, xor, not
3. Bitwise: bitand, bitor, bitxor, bitnot
4. Lists and words: first, bf, last, bl, item, se, list, word
5. Maps & co.: map, apply, foreach, run, remote
6. Loops and conditions: repeat, while, foreach, if, ifelse
7. Predicates: empty? number? list? word? equal? gt? lt? ge? le? member?
8. Variables and procedures: make, let, to, op, stop, erase, launch
9. NXT file handling: load, printto, fopen, fwrite, fread, fclose, fremove
10. Sounds: tone, sound
11. Motors, sensors: motor, readmotor, sensor, setsensor, battery
12. Other: wait, random, print, draw, ascii, char, boot, gc, fm

The expressions must be in prefix notation. Variables are used the same way as in Logo - as "name when referring to variable name, and as :name when referring to its value. There are global variables as well as local variables, lexical scoping as usual in Logo.

The (remote "expression) operations allow to start evaluating an expression on NXT when started from PC, and vice-versa. This can be used for communication. Of course, one could then easily say, for example:

remote "|[print "hello]|

or

remote "|[my_program 123]|

or read value of remote variable:

remote "|:var|

However, one has to keep in mind that BlueTooth communication is slow due to switching of the direction of the transceiver and receiver. Therefore, it is preferable to implement higher-level functions and procedures that can run on NXT brick autonomously. Logo programs have about 30kb of memory available - for storing both the logo programs and data, however, programs can load/erase data and code from NXT files that are stored in the large flash.

Examples

Some sample code for Logo for NXT is in the Examples folder.

Syntax

Detailed syntax is shown in the file syntax.txt.

Reference Guide

More detailed description of all commands and the system are located here: Logo for NXT Reference Guide.

Internals

Short specification of the Logo for NXT internals is in the file specification.txt.