© S. Ramesh / Kavi Arya / Krithi Ramamritham 1 IT-606 Embedded Systems (Software ) S. Ramesh Kavi...

1© S. Ramesh / Kavi Arya / Krithi Ramamritham

IT-606Embedded Systems

(Software)S. RameshKavi Arya

Krithi Ramamritham

KReSIT/ IIT Bombay


Esterel Tools & Illustrative Examples

S. Ramesh


Esterel Tools• Compiler

– C-code for simulation – C-code for target implementation in SW – bliff code for implementation in HW and

verification• Simulator - Xes• Verifer

– Xeve – fctools – atg


Make file - An example

all: blif genc obj es blif: esterel –Lblif :-soft -causal -main simple

auto.strl genc: esterel -simul -main simple auto.strl obj: gcc -w -c auto.c es: xes auto.o


The simulation tool - Xes


Verification Tools• Xeve

– converts bliff code into fc2 format – hiding of signals

• FcTools – Automata minimization – Automata abstractions

• Atg – display of automaton – Manual inspection


Code generator • Compiler (without special options) produces

– reactive engine that implements the automaton – one function for each input signal

• the reactive engine is just a procedure • user has to write a main program that calls the

engine • user has to write a function for each output

signal and sensor• when to call the engine, which input signals

are simultaneous decided by the user • the engine calls the output functions


ExampleMain:: every milli second for every input that has occurred call f_input(par); call f_kernel; end

• Assume interface functions run concurrently with the main program

• Input parameter gets the value from specific registers or memory

• f_kernel calls output functions corresponding to emitted outputs


A Simple Example

An Auto Controller:• initially waits for the engine to be on• when car is running,

acceleration/deceleration controls the throttle valve

• car stops when the ignition is off


The codemodule simple:input ignition_on,ignition_off,accel;output control_throttle;loop abort await ignition_on; every accel do emit control_throttle end every when ignition_off endend module


Use of Esterel Tools• compile the program to simulate (-simul

option)• compile the program to generate bliff code• use xeve to generate automaton• use atg for visual display


Automaton for Simple controller


A Complex Controller

Additional safety feature:• monitors status of the door (closed or

open) while in motion• sends out alarm when door opens• ensures that doors are closed while starting


The codemodule complex:input ignition_on,ignition_off,accel;input door_opened, door_locked;output alarm,control_throttle,door_lock; loop abort await ignition_on; emit door_lock; loop await door_locked; abort every accel do emit control_throttle end every when door_opened; emit alarm; emit door_lock; end; when ignition_off end end module


Automaton for Complex controller


Lego Mindstorm Robot


Mindstorms robots• Smart toys assembled using certain Lego

bricks called, Robotics Invention System– RCX brick (microcomputer), inspired by MIT

media lab. Programmable Brick– touch sensors– light sensor– Motors– IR Transceiver– Serial cable


RCX • Lego Micro computer

– 8 bit 16 MHz Hitachi controller– 8K ROM, 19K RAM– Supports three touch sensors, three motors and

one light sensor– Programmed using PC – Loaded using IR transmitter connected through

serial cable• Programmed using RCS programming language• Program receives sensor inputs and controls motor

movements


Synchronous Programming • Mindstorms can be programmed using

synchronous languages, like Esterel.• Thanks to an effort by some french groups

– http://www.emn.fr/x-info/lego//

• Makes use of LegOS, its tools and APIs


LegOS• An open source OS for lego Mindstorms

initiated by Markus L. Noga – Web page: http://www.noga.de/legOS/

• Supports (version 0.2.0)– Dynamic loading of programs and modules – Full IR packet networking – Preemptive multitasking – Dynamic memory management – Drivers for all RCX subsystems


Cross Compilation• The OS cross - compiled on a PC and

downloaded onto the RCX via IR transceiver• Runs in both Linux and windows• Provides many APIs for application

programs– Inputting from Sensors– Actuating motors

• Application programs (in C) use these APIs to control

• cross-compiled and loaded onto the RCX


Esterel Programming• Applications can be written in Esterel• An extension of Esterel compiler is

available• Need to use specific names for inputs and

outputs– touch_1, touch_3, motor_a_speed,

motor_b_speed, cputs etc.• Here is an example


A simple program module lego1 :

input TOUCH_1, TOUCH_3; output MOTOR_A_SPEED(integer),

MOTOR_C_SPEED(integer), MOTOR_A_DIR(integer),

MOTOR_C_DIR(integer), CPUTS(string); relation TOUCH_1 # TOUCH_3;

constant MOTOR_FWD, MOTOR_REV, MAX_SPEED : integer;


var t : integer in emit MOTOR_A_SPEED(MAX_SPEED/2); emit MOTOR_C_SPEED(MAX_SPEED/2);

loop emit MOTOR_A_DIR(MOTOR_FWD); emit MOTOR_C_DIR(MOTOR_FWD); emit CPUTS("fwd"); await [TOUCH_1 or TOUCH_3]; present TOUCH_1 then t:=1; else t:=3; end present;


emit MOTOR_A_DIR(MOTOR_REV); emit MOTOR_C_DIR(MOTOR_REV); emit CPUTS("rev"); await 100 tick; % 1 tick = 1 ms if t=1 then emit MOTOR_A_DIR(MOTOR_FWD); emit CPUTS("right"); else emit MOTOR_C_DIR(MOTOR_FWD); emit CPUTS("left"); end if; await 100 tick; % 1 tick = 1 ms end loop

end var.


Compiling

• This program can be simulated• Compiled using the extended compiler to

generate C code• Use legOS cross compiler to generate

code and download onto the RCX• Look at the web-site for more examples


A Simple Case-studyPlastic Injection Controller• a simple controller• controls a plastic injection unit.• The unit injects plastic material from a tank

into a molding chamber • When chamber is empty, a motor started in

the forward direction • motor moves a piston until it reaches

position B


Illustration (contd.)• motion is reversed until position A reached

in the opposite direction• plastic material in the tank heated by a coil• temperature of the tank controlled between

Tmin and Tmax


Time Constraints• motor must stop within in time units after

signals A and B are emitted as otherwise, the piston might get stuck

• contact switch made on/off within temp after temperature limits Tmin and Tmax reached to avoid boiling and keep it flowing


The code:module simple:

constant T_min=30:integer, T_max=100:integer;input A,B,form_empty;sensor Temp: integer;output motor_on(boolean), motor_off;output contact_on,contact_off;relation A#B;


[ loop if ?Temp<T_min then emit contact_on end; if ?Temp>T_max then emit contact_off end; await tick; end

||

loop await form_empty; emit motor_on(true); await B; emit motor_on(false); await A; emit motor_off; end]end module


Use of Esterel Tools


A Cruise Controller

A more complex auto controller:• includes the feature of cruise mode of

driving• illustrates the features like modules, valued

signals and procedure calls


module cruise:input cruise;input accel,brake_pressed;input engine_off;input accel_released,ignition_on;input belt_fastened,belt_unfastened;output chk_belts,start_engine;output control_throttle:double;output alarm;input current_speed:integer;output cruising;procedure increase_speed(double)(integer);procedure compute_throttle(double) (integer,integer);


loop await ignition_on; emit chk_belts; await belt_fastened; emit start_engine;


abort [ loop abort run manual_mode; when cruise; abort run cruise_mode; when

brake_pressed; end loop when engine_off end loop end module

|| every belt_unfastened do emit alarm end

]


module manual_mode:input accel_released,accel;output control_throttle:double;var th$_value:=5.0:double,val:=0:integer in loop abort every accel do emit control_throttle(th_value + 2.0); end every when accel_released; endend var end module


module cruise_mode:input current_speed:integer;output control_throttle:double, cruising;procedure compute_throttle(double) (integer,integer); var cruise_speed:=?current_speed:integer, th_value:double in cruise_speed:=?current_speed; every tick do call compute_throttle(th_value) (?current_speed,cruise_speed); emit control_throttle(th_value); emit cruising endend varend module


A Train Controller• controls the movement of an automatic

train• train moves back and forth between a set

of stations• no request means the train is idle at one of

the stations• request are serviced eventually• door is closed when the train is in motion• buttons are provided inside the train and in

the stations


module Train:input d_closed, d_opened, stn_arrived(integer);input request(integer);output d_close,d_open, t_run, t_stop;loop var X: integer inemit d_open;await d_opened;await request; X:=?request;emit d_close;await d_closed; trap Stop in


loop abort sustain t_run when stn_arrived; if X=?stn_arrived then emit t_stop; exit Stop; endend %loopend %trapend %varend %outer loopend module


A mine pump controller• controls a pump that drains excess water in the

mines• pump should start draining when water level is high• pump has to stop when water is too low• mine has methane which is combustible when the

pump is on• high dose of CO is lethal• warnings are to be issued• auto and manual mode for pump• pump is started and stopped under operator control• default is auto


module pump_controller:input start,stop,methane,co,hw_level;input lw_level,manual;input auto;output p_run,p_stop,m_alarm,c_alarm;[ loop abort loop await hw_level; await immediate [ not methane ]; abort sustain p_run


when [ methane or lw_level ]; emit p_stop end when manual; abortloopawait start;await immediate [ not methane ];abortsustain p_runwhen [methane or stop];emit p_stop;end


when auto;end loop||every methane doemit m_alarm;end every||every co doemit c_alarmend every]end module

© S. Ramesh / Kavi Arya / Krithi Ramamritham 1 IT-606 Embedded Systems (Software ) S. Ramesh Kavi...

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Transcript of © S. Ramesh / Kavi Arya / Krithi Ramamritham 1 IT-606 Embedded Systems (Software ) S. Ramesh Kavi...