The symbol ofp means this function is for ECHO-W2 only; all descriptions with this symbol are not suitable for ECHO-W1 A. PHYSICAL DESCRIPTIONS
1. LCD DISPLAY 2. MODE BUTTON 4. SET BUTTON 5. SILDE ON/OFF SWITCH 7. BRACKET 8. SENSOR MARKING LINE 10. SENSOR BATTERY CAP 11. SENSOR BAND 13. RING 14. MAGNET 16. 1.5V BATTERY (LR44 IS TYPICAL) 17. SCREW
6. Refer to the TEST section to testing the installation before tighten the sensor band with a screwdriver.(Fig. I) 7. Fix the excess sensor band 11 by thrusting it into the band carrier 12. (Fig. J)

English

1. The main unit has a "Slide On/Off Detecting Switch " (patents pending) to turn ON/OFF the power of the wireless receiver. It can receive the wireless wheel signal only after the main unit is slid onto the bracket. " 2. Spin the front wheel to check if installation is correct. Installation is correct if the main unit flickers " ". Please check the relative position symbol. It is an incorrect installation if there is no symbol of " among the main unit, the sensor and the magnet, or refer to the trouble-shooting table.
D. FUNCTIONS and SPECIFICATIONS : Current Speed
MX: Maximum Speed 0.0 199.9 Km/h or 120.0 Mile/h +/- 1% (Typical) / p : Speed Pacer : Lubrication Reminder: (For W2 only)
0.0 199.9 Km/h or 120.0 Mile/h

+/- 1%

It shows the highest speed from the last RESET operation. It flashes the " " speed pacer arrow while the current speed is higher than the average speed and the down arrow " " flickers conversely.
3. MAIN BATTERY CAP 6. RUBBER PAD 9. SENSOR (TRANSMITTER) 12. BAND CARRIER 15. 3V BATTERY (CR2032) 18. NUT
1. The current speed is always displayed on the upper display when riding. It displays current speed up to 199.9 KM/h or 120.0 M/h (for wheel diameters of over 24 inches). 2. When riding is stopped, the speed will continue to count 4 seconds for Bike 1 and count 2 seconds for Bike2 to confirm that no more wheel signals have been sent.

10.00 990.00 Km or Mile

+/- 0.1%

ODO: Odometer

0.0 99999.9 Km or Miles
B. INSTALLATIONS BRACKET AND MAIN UNIT MOUNTING
1. Attach the bracket to the handlebar and fit the rubber pad between the handlebar and the band of the bracket. Tighten the screw securely till the bracket cannot turn. (Fig. A) 2. Slide the main unit onto the bracket from front to rear till it clicks into position. To remove the main unit, press down on the lock lever of the bracket then pull the main unit forward and off. (Fig. B)
1. The odometer cumulates the total distance as long as the bike is running. 2. The ODO data can not be cleared to zero by RESET operation.
C. THE WIRELESS SYSTEM AND PERFORMANCES
1. The sensor transits the wheel rotating signal to the receiver in the main unit by the wireless transmission. To prevent the receiver from interfering by other wireless noises and causing the main unit to display false data, install the transmitter according to the following key points to get better performance. a). The receiver is designed to receive a signal with only a certain direction and angle to reduce the noise interference from other sources. Adjust the installation angle of transmitter to aim at the direction to the main unit within a +/- 15 angle, the best performance is at a vertical direction. b). The receiver will receive a stronger wireless signal if the transmitter is more close to the receiver. A stronger sensing signal not only has better noise immunity, but also increases the transmitter batterys operating life. For good wireless performance, please install the transmitter as close to the main unit as possible and within 45 cm (1.5 feet). 2. Precaution a). This computer has almost no cross-talking interference when 2 bicycles carrying the same or similar wireless cycle computers are ridden side by side, as long as the cross-distance is over 40cm (15.8). b). This computer has excellent noise immunity for some electromagnetic interference, but it may be interfered with by a strong electromagnetic wave and make the main unit displays error data while it is near strong interference such as TV transmission stations, radar stations, and some heavy industrial machines. 3. This computer has a Slide On/Off Detecting Switch to check the main unit to slide on/off from the bracket. a). To reduce the power consumption of the main unit to increase the battery operation life, but also to delete all indoor electromagnetic interference from electrical equipment (such as PC monitors, handy-phones, etc.). It will turn off the power supply of the receiver when the main unit takes off from the bracket. b). The main unit can only receive the wheel signal after it is slid onto the bracket.

p ODO1, ODO2 and T- ODO: Bike1, Bike 2 and Total Odometer (For W2 only)
1. The odometer cumulates the total distance as long as the bike is running, either Bike 1 or 2 has its odometer ODO 1 or ODO 2 individually. The T-ODO is the sum of the ODO 1 plus ODO 2. 2. The ODO1, ODO 2 or T-ODO data can not be cleared to zero by RESET operation.
1. This user-friendly function is created by ECHOWELL and patents are pending worldwide. It will remind you to lubricate your beloved bike after you preset the reminder. 2. The preset distance will be counted down, the LCD will flash the " " symbol when the preset distance will count down to 0 to remind you to lubricate your bike. 3. The reminding distance will count up after counting down to zero and the "o" symbol will display on the left of distance to indicate the distance is over the lubrication reminding distance if you did not reset the lubrication reminder.
: Maintenance Reminder: (For W2 only)
SENSOR AND MAGNET MOUNTING
1. Install the sensor and the sensor band 11 with the screw 17. (Fig. C) 2. Mount the band carrier 12 onto sensor band. (Fig. C) 3. Mounting the sensor unit on the right front fork with rubber pad. (Fig. D) 4. Mount the magnet 14 on one spoke of the front wheel and let the magnet face the sensors mark line. Place the ring 13 around the magnet to enhance the reliability of the fixed screw. (Fig. G) 5. Adjust the relative position between the main unit and the sensor, according to the following key points: a). It will receive a stronger wireless signal if the sensor is more close to the main unit. The arrow of the sensor must point to the main unit, and install the sensor as close to the main unit as possible and within 45 cm (1.5 feet) to get a better wireless performance. (Fig. F) It is workable when the arrow symbol is down (Fig. E), but keeping the arrow up is better because its sensing distance is shorter than with the arrow down. b). Adjust the installation angle of the sensor to aim at the direction of the main unit within +/- 15, the best performances is at vertical direction (90) between the sensors arrow and the battery cap of the main unit. (Fig. F) c). Adjust the magnet fixed position to let the center of the magnet align to the sensors marking line. (Fig. G) d). Adjust the sensor to let the gap between the magnet and the sensors marking line is about 5mm (0.2"). (Fig. H)
TM: Riding Time T-TM: Total Riding Time
0M00.0S-59M59.9S, 1H00M00S-99H59M59S 0H00M 9999H59M

+/- 0.003% +/- 0.003%

1. The TM totals the riding time from the last RESET operation. The T-TM accumulates total riding time from the beginning of computer use and can not be cleared by the RESET operation. 2. It will automatically begin counting upon riding, and continue to count 4 seconds for Bike1 and 2 seconds for Bike2 to confirm that no more wheel sensing signals have been sent when riding is stopped. But this computer revises back the over-counted 2 or 4 seconds automatically.

: 12HR AM/PM or 24HR Clock 0.003% AV: Average Speed
0:0000 12:5959 AM/PM or 23:5959 0.0 199.9 Km/h / 0.0 120.0Mile/h
It can display the current time in 12HR AM/PM or 24HR clock.
1. It is calculated from the DS divided by the TM. The average data counted is from the last RESET to current point. 2. It displays "0.0" when TM is less than 4 sec., and is updated by about one second when TM is over 4 seconds. 3. It displays an "Err" symbol when either the TM is over 100 hours or the DS is over 1,000km (or miles). Reset the unit in order to restart.
All descriptions are similar as the Lubrication Reminder except the word of Maintenance instead of Lubrication and the symbol " " shall be replaced by the symbol " ". Remarks: All functions data are updated about one second. Sensor with Transmitter: No Contact Magnet sensor with Wireless Transmitter. Suitable Fork Size: 12mm to 50mm& (0.5" to 2.0" &) Forks. Wireless Sensing Distance: 55cm (1.8 feet) between the transmitter and the main unit. Cross-Talking Interference: Within 40 cm (15.8"), no interference by 2 bicycles carrying similar cycle computers, even when ridden side by side. Wheel Circumference Setting: 1mm - 3999mm (1mm increment) Operation Temperature: 0C ~ 50C (32F ~ 122F) Storage Temperature: - 10C ~ 60C (14F ~ 140F) Main Unit Battery Power: 3V battery x 1 (CR2032), battery operating life is about 2 years. (Based on an average of 1.5 hours use per day) Transmitter Battery Power: 1.5V battery x 1 (typical LR44). About 24,000km/15,000 miles riding distance or 2 years battery operating life. (The original factory-attached battery life may be shorter than this period due to shipping and storage time).

Dimensions and Weight

Main Unit: 44.0 x 53.0 x 19.3mm/31.5g
Transmitter: 20.0mm& x 48.0mm/14.1g

DS: Trip Distance

0.00 999.99 Km or Miles
The DS function accumulates the distance data from the last RESET operation as long as the bike is being ridden.
* The specifications and designs may be changed without notice.

I NDEX:

MEANS PRESS BUTTON N MORE THAN 2 SECONDS. MEANS PRESS BUTTON N QUICKLY {N=KEYNUMBER: MODE Button. SET Button. }
p LUBRICATION or MAINTENANCE REMINDER SETTING (For W2 only)
p BIKE 1 or BIKE 2 SELECTION (For W2 only) (Fig. 2)
2. BATTERY CHANGE FOR SENSOR (TRANSMITTER)
a). The patent-pending transmitter circuit is designed to reduce power consumption; a 1.5V battery (typically an LR44) can operate for over 24,000km (15,000miles) riding distance or 2 years. b). Replace a new battery when the transmitters battery power is nearly exhausted, otherwise the transmission power of the wheel signal will be weak, causing the main unit to display unstable data. c). Replace with a new LR44 battery 16 with the positive (+) pole toward the sensor cap 10. (Fig. L)

E. MAIN UNIT SETUP (Fig. 1) INITIATE THE COMPUTER (ALL CLEAR)
1. A battery is already loaded in the main unit when purchased. Hold down the MODE button and SET button simultaneously for more than 3 seconds to initiate the computer and clear all data. IMPORTANT: Be sure to initiate the computer before it is be used, otherwise the computer may run errors. 2. The LCD segments will be tested automatically after the unit is initiated. to stop LCD test, then the flickering "KM/h". 3. Press the MODE button
1. The users friendly function is to remind you about lubricating or maintaining your beloved bike after presetting the desired reminding distance. 2. It displays the " " or " " symbol for Lubrication or Maintenance Reminder setting. (Default: Lubrication Bike1: 100 km or Miles, Bike2: 300km or Miles; Maintenance: Bike1:300km or miles, Bike2:990km or miles.) 3. Adjust the reminder distance data as described in the Data Setting Processes. 4. The function will be skipped if you set the distance at 000.00. 5. Press the SET button to store the desired data and change to the next setting.

CLOCK SETTING (Fig. b)

1. It displays the " " symbol at this clock setting. 2. 12H/AM, 12H/PM or 24H selection. to select 12H/AM, 12H/PM or 24H. Hold down the MODE button A quick press of the MODE button for more than 2 second to change to the clock setting screen. 3. Adjust the clock data according to the Data Setting Processes.
1. The ECHO-W2 design has 2 sets of circumference memory to calculate 2 bikes data separately. It also cumulates each Odometer, Lubrication and Maintenance reminding distance. 2. The Bike 1 is designed for MTB bikes and the Bike 2 is designed for racing bikes. 3. Hold down the MODE button for more than 5 seconds until it enters the bike selection screen. Dont worry if the LCD display is blank while the MODE key is held for over 2 seconds. The DS, MX, TM, AV data will keep no changes after Bike 1 or 2 is selected. a). Press the MODE button to change the Bike 1 or 2 selection. It displays wheel circumference c****. b). Hold the MODE key for over 2 seconds to store the selection and jump to the normal operation mode.

TROUBLE SHOOTING

PROBLEM CHECK ITEMS Main unit 1. Is the battery dead? No display 2. Is there incorrect battery installation? No current speed or Incorrect data 1. Is it at the MAIN UNIT SETUP or another setting screen? 2. Are the relative positions and gap between sensor and magnet correct? 3. Is the circumference correct? 4. Is the sensing distance too long or the installation angle of the sensor incorrect? 5. Is the sensor battery nearly exhausted? 6. Is any strong interference source nearby? REMEDY 1. Replace the battery. 2. Be sure that the positive pole of the battery is facing the battery cap. 1. Refer to the setting procedure and complete the adjustment. 2. Refer to (Fig. G) and (Fig. H) and re-adjust position and gap correctly. 3. Refer to "Circumference Setting" and enter correct value. 4. Refer to (Fig. F) to adjust distance or angle between the main unit and the sensor. 5. Replace with a new battery. 6. Move away from the source of interference. Refer to the "Main Unit Setup" and initiate the computer again. Place main unit in the shade to return to normal state. No adverse effect on data. Unit will return to normal state when the temperature rises.

CIRCUMFERENCE, CLOCK, LUBRICATION AND MAINTENANCE REMINDER RE-SETTING
1. Press the MODE button to change to one of the following mode displays. a). Change to ODO screen to set Circumference. b). Change to screen to set Clock. (Fig. b) c). Change to screen to set Lubrication Reminder only. d). Change to screen to set Maintenance Reminder only. e). Change to DS screen to set both Lubrication and Maintenance Reminders. to enter to the relative setting screen. 2. Press the SET button 3. Adjust the desired value according to the Data Setting Processes. to store the desired data and complete the current setting. 4. Press the SET button

UNIT SELECTION

Press MODE button to choose KM/h or M/h (Mile/h). Press the SET button to recognize either as desired.
ODO1, ODO2 and T-TM DATA SETTING (ODO2 Is only for W2)
1. The function is designed to re-key in former data of ODO1, ODO2 and T-TM when battery is replaced. A new user does not need to set this data. Each press of the SET button skips one setting data process. 2. Data Setting Processes (621 741): (Fig a) A). The data is adjusted per each digit separately. The digit to be set flickers. B). Press the MODE button to increase the digital value by 1. C). To change the setting digit by hold down the MODE button for more than 2 seconds. D). Press the SET button to store the data and change to the next setting.
F. BUTTON and NORMAL OPERATIONS MODE BUTTON (Fig. 5)
1. Quickly press this button to move in a loop sequence from one function screen to another. 2. It skips the T-TM, ODO, T-ODO, Lubrication and Maintenance Reminder function data while it riding.
CIRCUMFERENCE DATA SETTING (Default Bike 1)
1. It displays the c2155of the default value 2155mm. Measure the value for your wheel or refer to the quick table provided in the manual for your bicycle. 2. Adjust the circumference data as described in the Data Setting Processes. 3. The LCD will change to the Clock setting screen for W1 or change to the Lubrication Reminder setting screen for W2 after the "SET" button is pressed to store the desired data.
SET BUTTON Press this button to get in or out the setting screens when you want to re-set to bike circumference, Lubrication reminder, Maintenance reminder or the current time of the " ". RESET OPERATION (Fig. 6 )
till the LCD digit is blanked, then release it. The computer will reset AV, 1. Hold down the MODE button DS, TM and MX data from stored values to zero. 2. It cannot reset ODO, T-TM, , T-ODO, Lubrication and Maintenance Reminders.

p RE-LOAD LUBRICATION OR MAINTENANCE REMINDER AFTER MAINTAINED (For W2 only)
In order to avoid the Lubrication or Maintenance reminder be cleared by the RESET operation, be follow the following procedures to RE-LOAD the previous setting value after you finish either function. or screen. (Fig. 3 & 4) 1. Change it to the desired to display the previous setting value and clear the reminder symbol. 2. Press the SET button again to re-load the previous setting value and jump to the normal operation. 3. Press the SET button
Irregular display LCD is black Display is slow
MAIN UNIT SLIDE ON/OFF DETECTION
The computer has a slide on detecting switch (patents pending) to avoid noise interference when the main unit is removed from the bracket. The main unit can receive the wheel signal only when it is slid onto the bracket only.
Did you leave main unit under direct sunlight when not riding the bike for a long period of time? Is the temperature below 0C (32F)?

WHEEL CIRCUMFERENCE

Precise Measurement (Fig. M) Roll the wheel until the valve stem is at its lowest point close to the ground, then mark this first point on the ground. Get on the bicycle and have a helper push you until the valve stem returns to its lowest point. Mark the second point on the ground. Measure the distance between the marks. Enter this value to set the wheel circumference. Quick Table (Fig. N): Get a suitable circumference value from the table.
AUTOMATIC START/STOP & POWER AUTO ON/OFF
The computer will automatically begin counting data upon riding and stop counting data when riding is stopped. The flickering symbol " " indicates that the computer is at start status. To preserve battery, this computer will automatically switch off and just displays the " " data when it has not been used for about 30 minutes. The power will be turned on by pressing the MODE button.
G. BATTERY CHANGE 1. MAIN UNIT BATTERY CHANGE
a). The symbol " " will appear to indicate the battery is nearly exhausted. b). Replace the battery with a new battery within a few days after the symbol was appeared. c). All data will be cleared when battery is replaced, but this computer allows you to re-key in ODO1, ODO2 and T-TM which you had rode after replacing battery, keeping record these data before you remove the old battery. d). Replace with a new CR2032 battery 15 (Fig. K) and initiate the main unit. (Fig. 1)

PRECAUTIONS

1. Dont leave the main unit exposed to direct sunlight when not riding the bike. 2. Dont disassemble the main unit or its accessories. 3. Check relative position and gap of sensor, magnet and main unit periodically. 4. Dont use thinner, alcohol or benzine to clean the main unit or its accessories when they become dirty. 5. Remember to pay attention to the road while riding.

Implementation of a simple shell, xssh

What is a shell?

A process that does command line interpretation Reads a command from standard input (stdin) Executes command corresponding to input line In simple case the shell: Reads a command Forks a child to execute the command Wait for child to complete before reading another command.
A real shell handles: Foreground process groups Background process groups Signals Process pipelines Redirection

The UNIX Shell

A shell is a command line interpreter Translates commands typed at a terminal (or in a file) Input is from the terminal (stdin) or file Users /etc/passwd entry indicates the interactive shell Some Shells Bourne Shell (sh): What some use for shell scripts C-Shell, TC-Shell (csh, tcsh): Typical interactive shell Bash Shell (bash, GNU Bourne-Again Shell): Default Linux interactive shell

Shell Scripting

Shell Script (Shell Program) A file containing shell commands Used heavily in system administration Scripts in /etc/rc*.d/ are executed during system booting A Tutorial on Scripting: www.ooblick.com/text/sh

Input and Output

< File Use File as standard input (stdin) Note: stdin is file descriptor (fd 0) > File Use File as standard output (stdout, fd 1) << Word Read from the current file until end of file
or an input line containing Word alone >> File Append stdout to File Command1 | Command2 Create a pipeline
Connect stdout of Command1 to stdin of Command2
Parameter/Command Substitution
${Parameters} indicates parameter substitution The result of substitution is the value of the parameter e.g., $X
X=foo echo $XX echo ${X}X # output is null string # output is fooX
Parameters A Name: A sequence of letters, digits or underscores starting with a letter A Number: $1 is the first command line argument, $2 is the second, etc. (positional parameters) Special Parameters: * @ # ? - $ !

Special Parameters

Equivalent to "$1 $2." $@ Equivalent to "$1" "$2",. $# Number of positional parameters $$ Process number of this shell $? Value returned by last executed command in decimal $! Process number of last background command $- Options supplied to shell on invocation or by set

Our simple shell: xssh

By developing a shell from the button up we explore

the intricacies of:

Process creation

Process termination

Process identification Correct handling of signals (future?)

What will our shell do?

Execute built-in commands Execute foreground processes Execute background processes Perform variable substitution before executing
command Perform redirection Ignore comments and blank lines Implement optional features?

Built-in commands

echo W1 W2 W1, W2,. are words Compress consecutive white spaces to a single space quit S Exit shell with exit status S, an integer Real shell allows bg processes to continue; xssh shouldnt !!! wait P Wait for process P to terminate; If P is omitted, wait for all background processes to terminate

Built-in commands (2)

set V Val The shell replaces all occurrences of $V with Val, the value of V unset V Remove given variable Special variables: $$ pid of current process, $? exit status of most recent command $! pid of most recent background process NOTE: All shell variables are environment variables

Built-in commands (3)

chdir P Change PWD to P, a pathname (same as cd) Assume $HOME if P is omitted The user must have permission to cd to P or else permission denied

Non built-in commands

Built-in commands evaluated without fork-exec If first word is not a built-in command: it must be a command found in a directory listed in $PATH
Directory names are separated by colon (:)
Must be evaluated with fork-exec

Strategy

What are the requirements? Are there assumptions? What is most critical? What are the risky parts of the project? What are the main data structures? i.e., Abstract data types (data and function members) What is the overall control flow? What system calls/library functions will be needed?
Can you sketch the whole project on a sheet of paper? Assume simple implementations of each feature

Risky parts

eviron Display the environment variables HOME, PWD, PATH

getenv(3)

These are the ONLY environment variables
The root shell inherits the env vars from its parent They should be automatically passed to any children

chdir P Easiest approach

Use chdir(2) to actually change directory Use putenv(3) to set PWD chdir(2) only affects the process that calls chdir
Can also find where you are by calling getcwd(3)
quit S Need to cleanup and wait for background processes
wait P Need list/table of background processes Non-builtin commands fork-execvp-wait Variable substitution Should be separable code; i.e., inserted before command processing

Observations

All system calls and error-prone library functions

should be wrapped

E.g. static inline pid_t Fork(void) {.} in stdinc.h

Basic Control Flow

main: Initialize; while (get line not EOF) { Break line into words; if (builtin command) else }
do_builtin; do_nonbuiltin;
do_builtin: if (incorrect #args) { Display msg; return; } case command { // or directly call function. chdir,echo,quit,wait,set. }

// optional

do_nonbuiltin: if ((pid=Fork( )) error). Error. if (pid == 0) { // child. execvp code. exit(0); } Wait for child to terminate;