Read Data From Serial Port Javascript For Loop

EaziF.png' alt='Read Data From Serial Port Javascript For Loop' title='Read Data From Serial Port Javascript For Loop' />LZW Data Compression. Dr. Dobbs Journal. October, 1. 98. 9Note I have an updated article on LZW posted here. Please check out the new article and tell me what you think. I hope it improves on this post and makes LZW easier to understand. Thanks to Jan Hakenberg for correction of a couple of errors In Figure 4, the values for new table entries 2. Thanks to David Littlewood for pointing out the missing line of pseudocde in Figure 6. Thanks to Joe Snyder for pointing out a line where a macro should replace a hard coded constant. Any programmer working on mini or microcomputers in this day and age should have at least some exposure to the concept of data compression. In MS DOS world, programs like ARC, by System Enhancement Associates, and PKZIP, by PKware are ubiquitous. ARC has also been ported to quite a few other machines, running UNIX, CPM, and so on. CPM users have long had SQ and USQ to squeeze and expand programs. Unix users have the COMPRESS and COMPACT utilities. Getting input from the Arduino serial monitor window. Using, checking and converting serial port input. How to get a string and number into the Arduino from the. Responses to Building An Active RFID People Asset Tracking System With Mesh Networking RFID tracking system Hack a Day Says February 21st, 2010 at 12. Serial tutorial More than you ever wanted to know about serial communications with the Particle Photon and Electron. Updates to this document are here httpsgithub. InformationWeek. com News, analysis and research for business technology professionals, plus peertopeer knowledge sharing. Engage with our community. A wide range of single, dual multi channel data loggers suitable for logging to fully assembled bespoke systems for data acquisition. GPS, GPRS, GSM etc. Libraries for Arduino. This page includes a list of community contributed libraries for Arduino. Check out the Official Arduino Libraries or Interfacing With Hardware. Free HTML Website Maker. Create awesome website with slideshow in seconds. For Mac and WindowsIve been playing with the Arduino sleep modes and i wanted to be able to wake up from the sleep when receiving data on the serial port. Mainly, because in my. This document defines a set of ECMAScript APIs in WebIDL to allow media to be sent to and received from another browser or device implementing the appropriate set. Yet the data compression techniques used in these programs typically only show up in two places file transfers over phone lines, and archival storage. Data compression has an undeserved reputation for being difficult to master, hard to implement, and tough to maintain. Read Data From Serial Port Javascript For Loop' title='Read Data From Serial Port Javascript For Loop' />In fact, the techniques used in the previously mentioned programs are relatively simple, and can be implemented with standard utilities taking only a few lines of code. This article discusses a good all purpose data compression technique Lempel Ziv Welch, or LZW compression. The routines shown here belong in any programmers toolbox. For example, a program that has a few dozen help screens could easily chop 5. K bytes off by compressing the screens. Or 5. 00. K bytes of software could be distributed to end users on a single 3. K byte floppy disk. Highly redundant database files can be compressed down to 1. Once the tools are available, the applications for compression will show up on a regular basis. Read Data From Serial Port Javascript For Loop' title='Read Data From Serial Port Javascript For Loop' />LZW Fundamentals. The original Lempel Ziv approach to data compression was first published in in 1. Terry Welchs refinements to the 1. The algorithm is surprisingly simple. In a nutshell, LZW compression replaces strings of characters with single codes. It does not do any analysis of the incoming text. Instead, it just adds every new string of characters it sees to a table of strings. Compression occurs when a single code is output instead of a string of characters. The code that the LZW algorithm outputs can be of any arbitrary length, but it must have more bits in it than a single character. The first 2. 56 codes when using eight bit characters are by default assigned to the standard character set. The remaining codes are assigned to strings as the algorithm proceeds. The sample program runs as shown with 1. This means codes 0 2. Compression. The LZW compression algorithm in its simplest form is shown in Figure 1. A quick examination of the algorithm shows that LZW is always trying to output codes for strings that are already known. And each time a new code is output, a new string is added to the string table. Routine LZWCOMPRESSCODE STRING get input character. WHILE there are still input characters DO    CHARACTER get input character    IF STRINGCHARACTER is in the string table then        STRING STRINGcharacter    ELSE        output the code for STRING        add STRINGCHARACTER to the string table        STRING CHARACTER    END of IFEND of WHILEoutput the code for STRING The Compression Algorithm. Figure 1. A sample string used to demonstrate the algorithm is shown in Figure 2. The input string is a short list of English words separated by the character. Stepping through the start of the algorithm for this string, you can see that the first pass through the loop, a check is performed to see if the string W is in the table. Since it isnt, the code for is output, and the string W is added to the table. Since we have 2. 56 characters already defined for codes 0 2. Read Data From Serial Port Javascript For Loop' title='Read Data From Serial Port Javascript For Loop' />After the third letter, E, has been read in, the second string code, WE is added to the table, and the code for letter W is output. This continues until in the second word, the characters and W are read in, matching string number 2. In this case, the code 2. The process continues until the string is exhausted and all of the codes have been output. Input String WEDWEWEEWEBWETCharacter Input. Code Output. New code value. New StringW2. 56WEW2. WEDE2. 58. EDD2. DWE2. WEE2. EWEE2. 60. 26. WEEW2. EWEB2. 57. WEBB2. BWET2. 60. WETEOFTThe Compression Process. Figure 2. The sample output for the string is shown in Figure 2 along with the resulting string table. As can be seen, the string table fills up rapidly, since a new string is added to the table each time a code is output. In this highly redundant input, 5 code substitutions were output, along with 7 characters. If we were using 9 bit codes for output, the 1. Of course, this example was carefully chosen to demonstrate code substitution. In real world examples, compression usually doesnt begin until a sizable table has been built, usually after at least one hundred or so bytes have been read in. Decompression. The companion algorithm for compression is the decompression algorithm. It needs to be able to take the stream of codes output from the compression algorithm, and use them to exactly recreate the input stream. One reason for the efficiency of the LZW algorithm is that it does not need to pass the string table to the decompression code. The table can be built exactly as it was during compression, using the input stream as data. This is possible because the compression algorithm always outputs the STRING and CHARACTER components of a code before it uses it in the output stream. This means that the compressed data is not burdened with carrying a large string translation table. Routine LZWDECOMPRESSCODE Read OLDCODEoutput OLDCODEWHILE there are still input characters DO    Read NEWCODE    STRING get translation of NEWCODE    output STRING    CHARACTER first character in STRING    add OLDCODE CHARACTER to the translation table    OLDCODE NEWCODEEND of WHILE The Decompression Algorithm. Figure 3. The algorithm is shown in Figure 3. Just like the compression algorithm, it adds a new string to the string table each time it reads in a new code. All it needs to do in addition to that is translate each incoming code into a string and send it to the output. Figure 4 shows the output of the algorithm given the input created by the compression earlier in the article. Drivers Microsoft Activesync 4.5 there. The important thing to note is that the string table ends up looking exactly like the table built up during compression. The output string is identical to the input string from the compression algorithm. Note that the first 2. Input Codes W E D 2. E 2. 60 2. 61 2. 57 B 2. TInputNEWCODEOLDCODESTRINGOutput. CHARACTERNew table entryWWW2. WEWEE2. 57 WEDEDD2. ED2. 56. DW2. 59 DE2. EE2. 60 WE2. 60. EWE2. E2. EE2. 62 WEE2. WEW2. 63 EWB2. BB2. WEB2. 60. BWE2. 65 BT2. TT2. 66 WETThe Decompression Process. Figure 4. The Catch. Unfortunately, the nice simple decompression algorithm shown in Figure 4 is just a little too simple. There is a single exception case in the LZW compression algorithm that causes some trouble to the decompression side. Arduino sleep mode Waking up when receiving data on the USARTIve been playing with the Arduino sleep modes and i wanted to be able to wake up from the sleep when receiving data on the serial port. Mainly, because in my project Im using the XBee in the API mode and the tricks exposed in http www. LearningArduino. Sleep. Code and http www. SavepowerinSquid. Bee sleepmode involve putting Arduino in SLEEPMODEPWRDOWN and using an extra pin on the arduino to monitor the RX pin and detecting LOW. I didnt like that much that solution so I started to look into other ways of doing it without using an extra pin and without risk of losing data in the serial interface. Because as I understood it using SLEEPMODEPWRDOWN requires to send first a burst of data to the serial interface in order to wake up the arduino. And it takes a while for the Arduino to become fully functional so that means that you will losemiss data in the serial interface. That was something that didnt fit my project. In order to be able to sleep but without missing serial data I used POWERMODEIDLE, a power saving mode that leaves the USART on and then using the functions defined in power. I disabled all other modules that I dont need to cut down the power consumption. When any data is received in the USART the Arduino will be brought back to normal power mode USART uses interrupts and any interrupt makes the ATmega. See the actual code below or in gist Sleep Demo Serial. Example code to demonstrate the sleep functions in a Arduino. Arduino will wake up. USART. Based on Sleep Demo Serial from http www. LearningArduino. Sleep. Code. Copyright 2. Mac. Simski 2. 00. Copyright 2. 00. D. Cuartielles 2. Mexico DF. With modifications from Ruben Laguna 2. This program is free software you can redistribute it andor modify. GNU General Public License as published by. Free Software Foundation, either version 3 of the License, or. This program is distributed in the hope that it will be useful. WITHOUT ANY WARRANTY without even the implied warranty of. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the. GNU General Public License for more details. You should have received a copy of the GNU General Public License. If not, see lt http www. Status0 variable to store a request for sleep. Serial. begin9. 60. NowNow is the time to set the sleep mode. In the Atmega. 8 datasheet. In the avrsleep. The 5 different modes are. SLEEPMODEIDLE the least power savings. SLEEPMODEADC. SLEEPMODEPWRSAVE. SLEEPMODESTANDBY. SLEEPMODEPWRDOWN the most power savings. SLEEPMODEIDLE sleep mode is set here. THE PROGRAM CONTINUES FROM HERE AFTER WAKING UP. Serial. printAwake for Serial. Serial. printlnsec count delay1. Serial. availableintvalSerial. SSerial. printlnSerial Entering Sleep mode delay1. Serial error otherwise Now sleep function called here. ASerial. printlnHola Caracola classic dummy message. Serial. printlnTimer Entering Sleep mode delay1. Serial error otherwise Now sleep function called here.