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275 lines
17 KiB
275 lines
17 KiB
\documentclass[11pt]{article}
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%Gummi|065|=)
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\usepackage{graphicx}
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\usepackage{caption}
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\usepackage{xcolor}
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\usepackage[vcentering,dvips]{geometry}
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\geometry{papersize={6in,9in},total={4.5in,6.8in}}
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\title{\textbf{Air Quality Sensor}}
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\author{Steak Electronics}
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\date{2018 (revised 2019)}
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\begin{document}
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\maketitle
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\tableofcontents
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\textcolor{green!60!blue!70}{
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\section{Overview}}
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To know when I need to clean my room. I usually vacuum every two or three weeks, but sometimes am lazy and I need a reminder. The dust sensor will be more motivation to get me to clean, when I see the dust levels increase. \footnote{Technically, I also get a rash from excess dust, which is another great motivator.}
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\begin{center}
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\includegraphics[scale=0.3]{../pics/dustsensor.JPG}
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\captionof{figure}{Shinyei Dust sensor PPD42}
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\end{center}
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\textcolor{green!60!blue!70}{
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\section{Work Log}}
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\textcolor{green!60!blue!70}{
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\subsection{Parts List}}
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\begin{itemize}
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\item Shinyei PPD42NS Air Quality Sensor
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\item MSP-EXP430G2553 V1.5
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\item 5V adapter (required as MSP is 3.3V only)
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\item SD Card adapter
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\item Ethernet Module
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\item Energia version 0101E0012 (or later, possibly)
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\end{itemize}
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\subsection{Beginning}
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Here are some things I learned working on this project.
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\textbf{IDE}
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I'm using Energia from energia.nu which is an Arduino IDE clone for TI Launchpads. This will allow for rapid development. And ease me into the TI platform.
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\textbf{MSP-EXP430G2 V1.5}
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There are different version of this. My particular board is the
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and as explained here: http://energia.nu/pin-maps/guide\_msp430g2launchpad/ and http://energia.nu/pin-maps/guide\_msp430g2launchpad/
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You need to rotate the UART jumpers to get UART to display correctly. Oddly enough you can choose a different chip in the boards list and serial will print out right... But switch the jumpers and the correct board will work with UART. Otherwise, it does not work out of the box for serial.print. Though the blink example sketch works.
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\textbf{Dust Sensor}
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The code for the dust sensor is found online easily. The pinout is tricky as the colours of the wire are nonsense, but the pinout seems to be the same for all sensors, and is: PIN 1 (closest to black box) GND, PIN 3, VDD (5+V), PIN 4 output A. there is also an output B for different readings (I think size) of dust. I'm not that particular (no pun intended) about my dust so I will go with the one most people are using.
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\textbf{3.3V only on TI}
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The TI takes input of USB but only outputs 3.3V. Fail. I'll through a 5V PSU on the board. It won't be connected to USB for its use anyways.
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\textbf{POW function}
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There is a pow function (power exponent) in arduino. In TI, I changed it to powf, and included math.h.
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I'm not sure if my change was correct.
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EDIT: looks like there is a LED tied to pin 14. I'm moving to pin 13. I meant to use 13 earlier but accidentally used the wrong pin and kept using it. Oops.
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EDIT 2: Actually, I was reading from the wrong pin in software. Maybe I will leave it on the LED pin as you can see when the dust is firing off the sensor. Hm.... Neat.
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EDIT 3: Yes, so I had to use powf instead of pow, and it works. The accidental incorrect pin was a bonus as it allows me to see visually how often the sensor is going off. Over time, I should have a vague grasp of the dust levels just looking at the light. Actually, I won't. Nevermind. The dust sensor reading, is too irregular for that.
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\textcolor{green!60!blue!70}{
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\subsection{Work Log 08/2018}}
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I've put everything on a single piece of plywood, and need to do some more work on the code. I've decided to forgo the SD card, as I don't want to deal with reading a 2MB sd card with the buffer provided by the SRAM. I'm not quite sure how to manage that, and whether it's possible to read such large data files. I did some quick research and did not find what I wanted. It is likely possible, but let's do something simpler. Instead, I will use the EEPROM to store the last 5 minutes of data or so, and then have the server read the data every five minutes. This keeps the client simple, and puts the burden of complexity on the server.
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In addition, I don't want to read SD cards manually, as that is cumbersome, though possibly scripts could be made.
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The PPD42 was made sure to be put vertically.
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\begin{center}
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\includegraphics[scale=0.3]{../pics/woodboard.JPG}
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\captionof{figure}{Everything on a piece of plywood, is a nice presentation. Sand and finish with urethane as well.}
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\end{center}
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\textcolor{green!60!blue!70}{
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\subsection{Work Log 12/2018}}
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I have decided to change how I do this slightly. Instead of an SD card, I will connect on the LAN and use thingspeak from a locally hosted instance (and deployed with docker, possibly) or some other aggregating server to pull the data. I'll also make a shield, to simplify deployment. That might not be necessary, but I can make a shield in a few hours, and pcbs are cheap. These options such as thingspeak sometimes have graphing / plotting included.
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I'm going to use this library:
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https://github.com/reaper7/EtherEncLib/releases
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so git clone that, then
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git tags -l
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git checkout tags/v0.4.2
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to get the latest release (or a newer one if possible).
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The pinout for the ENC is viewable at the figure to the right. This is from the 43oh.com forum.
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\footnote{You will see later, that this library turns out to be not developed enough, and results in overall failure for this project. Next time, use a well vetted library!}
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\textcolor{green!60!blue!70}{
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\subsection{PCB Layout}}
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Layout is simple for the most part. I again, flipped the ENC as I had done on the Uno board, so it is inserted upside down on the board. This time I went only with the 2x5 pin enc for simplicity sake. The shield is below the MSP, so longer pin headers will be used (already have those) to give space for the barrel plug. The board needs a 3.3v regulator and 5v for the PPD42. To get the sizing of the shield right, I aligned my grid with that of the design files for the msp430 dev board, and made sure the spacing between the 0.1” headers was exactly the same – easy. Ran all traces of 20 mils and made the board small as reasonably possible. Now to get them made, and actually test this.
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\textcolor{green!60!blue!70}{
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\subsubsection{Aligning shield with Eagle and KiCad}}
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So here was an interesting segway. I had design files in Eagle, and I wanted to make a shield for the MSP in Kicad. What I did, was align the grid in Eagle, to be the same as Kicad, and then as appropriate, sized points on the Kicad grid to fit exactly where the MSP shield was. In fact, it turned out 100\% correct the first try. Here is where FOSS and OSHW worked out well. Without the design files (say if I had only a PDF with some measurements), I can't say it would've turned out as well. Open file formats for all components and shields!
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\begin{center}
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\includegraphics[scale=0.5]{../pics/pcblayout.jpg}
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\captionof{figure}{See caption on picture.}
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\end{center}
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\textcolor{green!60!blue!70}{
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\subsection{Revision 1 Results}}
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I built up the PCB today. A few errors were made, but this is much better than the mess I had on the plywood originally. First off, the ENC pins are wrong, so that is not going to be able to be mounted (unless I wanted to wire pins manually). Second, the orientation of the MCP part is wrong. I'm not sure how this was done incorrectly, but I suspect that the default KiCad libraries were wrong. I have a few other changes to do, but this was overall successful, and I can respin another board quick quickly. On my todo list is:
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\begin{itemize}
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\item add gnd breakout
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\item add 5v breakout
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\item add 3v3 to enc NOT 5v
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\item fix enc pins
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\item fix orientation of main board
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\item add anime picture to back of board
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\item fix orientation of 3v3 reg
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\item buy more msps (need two more at least)
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\item buy 100 1uf 0805 caps put in main box (I'm surprised I don't keep these in stock. I do have through hole 1uf but not 0805).
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buylist + pcb : header so you can just plug in ppd. This is a sort of wish list thing, but something that will save a few seconds on build time. Although NOT necessary.
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\end{itemize}
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It looks like the connector between the board to the PPD42 is a type of 2.54 or 0.1” header. I will add a separate connector for the PPD42 that has all five pins. No need for any special connector.
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\textcolor{green!60!blue!70}{
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\subsection{BOM Creation Notes}}
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Here's some notes on creating the BOM.\footnote{This is a tounge in cheek reference to automated searches for weapons, etc... Yes, the algorithms read everything on every computer.}
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The MSP-EXP430G2 is being obsoleted, in favor of the MSP-EXP430G2ET. This is not a good thing, and shows poor sport on TI's part. I was always wary of the two dozen MSP430's, and now they are removing the original one from production, according to digikey. Ugh. Makes me think I should've just used an Arduino, but I digress.
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Planned obsolecense means, I'll have to make my own dev board for a TI part next time. Which I may just do, the chip is simple enough, and if ICSP and energia will work with this (which I found after a short search on the 43oh.com forums), then that is good enough.
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\textcolor{green!60!blue!70}{
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\subsection{Work Log 01/24/19}}
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Adding Library to Energia
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The path for adding a library to energia is:
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/home/dev/Desktop/code/electronics/airqualitysensor/energia-0101E0012/hardware/msp430/libraries
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on my machine. The idea is to add the library to the libraries folder (but, NOT the lib folder…, a little confusing). And you might have to hunt to find that. So I git cloned the ethernet lib, and added it in Remember that this ENC library works with only certain launchpads. Including, my now OBSOLETE one. F\$\#\% companies, and their obsolescence. There’s a special place in hell for these people.
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Upon adding the Ethernet libraries, and running websrv example, I get this error:
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fatal error: avr/pgmspace.h: No such file or directory
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compilation terminated.
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After some fumbling, t looks like
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https://github.com/energia/Energia/commit/cafa204a33e6e0dfa65b2f97dd14792a5964837e
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is what I should be using.
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Make sure you grab from the msp430 section, not the other cores… There’s only two header files, and one short c file. Then it’s all dupes for different cores (not sure if 100\% alike, but we only want msp430).
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This library is poorly done. Had to manually add an include to EtherEncLibUdp.cpp for the dtostrf.h file. I also had to put that file somewhere it could be found. I think you can put it in the etherenc library folder, but perhaps I'm wrong and it should be in the reference folder of Arduino. One of those places.
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\begin{center}
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\includegraphics[scale=0.4]{../pics/DSCN1146.JPG}
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\captionof{figure}{Shield PCB and PPD42}
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\end{center}
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After that it builds.
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With the default example, you have to change a pin. It’s the CS pin that is wrong. I think it’s by default pin 10, but on the pin mappings, it should be 8 (see image in pics folder). There’s two places to change this. One in the sketch (obvious). The second is in etherenclib somewhere… I saw this mentioned in the post in resources I have saved, so refer to that in the git repo.
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Ah, looks like I also forgot to solder some pins. Oops. After that’s out of the way, let’s look at the pin mappings.
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Quote: “(you can change this pin in file enc28typedef.h - line 424, then also mandatory! in sketch pinMode(10,OUTPUT);”
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Says the forum post. I believe it’s this:
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\begin{verbatim}
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#if (ENERGIA)
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#define ENC28J60_CONTROL_CS 8
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//#define SPI_MOSI 13
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//#define SPI_MISO 12
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//#define SPI_SCK 14
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\end{verbatim}
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And with that, I was able to get this to work. Note that pings do NOT work. It should do nothing if you ping. If you are getting destination not found, then something is wrong. Pings simply reach a dead end. Now to incorporate this with the air quality sensor.
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At first, I had some memory issues. This TI chip has 512 Bytes of SRAM (compared to Atmega328p's 2K SRAM), so I had to do some cutting down of the code. Here's a short interlude where I did this. NOTE: Later on I simplified the code even more.
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\textcolor{green!60!blue!70}{
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\subsubsection{ENC28J60 on TI Launchpad Code Troubleshooting}}
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\begin{verbatim}
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Basic Server test
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Works.
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Basic Sensor test
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Works
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Basic Sensor and Server test
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Fails. Out of memory.
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\end{verbatim}
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Let’s see at what point, the basic combination of server and sensor fails… What is pushing it over the barrier… I can put math.h and go through setup – no problem…
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Ok, it’s this block of code:
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\begin{verbatim}
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if ((millis()-starttime) > sampletime_ms)//if the sample time == 30s
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{
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ratio = lowpulseoccupancy/(sampletime_ms*10.0); // Integer percentage 0=>100
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concentration = 1.1*powf(ratio,3)-3.8*powf(ratio,2)+520*ratio+0.62; // using spec sheet curve
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Serial.print(lowpulseoccupancy);
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Serial.print(",");
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Serial.print(ratio);
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Serial.print(",");
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Serial.println(concentration);
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lowpulseoccupancy = 0;
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starttime = millis();
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}
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\end{verbatim}
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Let’s cut it down. Interestingly this code here, jumps up 4K bytes:
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\begin{verbatim}
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if ((millis()-starttime) > sampletime_ms)//if the sample time == 30s
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{
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//ratio = lowpulseoccupancy/(sampletime_ms*10.0); // Integer percentage 0=>100
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//concentration = 1.1*powf(ratio,3)-3.8*powf(ratio,2)+520*ratio+0.62; // using spec sheet curve
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Serial.print(lowpulseoccupancy);
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Serial.print(",");
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Serial.print(ratio);
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Serial.print(",");
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Serial.println(concentration);
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lowpulseoccupancy = 0;
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starttime = millis();
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},
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\end{verbatim}
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even with ratio and concentration cut out. From about 10K to 14K bytes. Wow.
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If I do this:
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\begin{verbatim}
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if ((millis()-starttime) > sampletime_ms)//if the sample time == 30s
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{
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//ratio = lowpulseoccupancy/(sampletime_ms*10.0); // Integer percentage 0=>100
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//concentration = 1.1*powf(ratio,3)-3.8*powf(ratio,2)+520*ratio+0.62; // using spec sheet curve
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Serial.print(lowpulseoccupancy);
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//Serial.print(",");
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//Serial.print(ratio);
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//Serial.print(",");
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//Serial.println(concentration);
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lowpulseoccupancy = 0;
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starttime = millis();
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}
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\end{verbatim}
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It’s back to about 10K bytes. So the serial prints, are a bit wild. I actually don’t need serial prints at all. Let’s cut those out.
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\begin{verbatim}
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ratio = lowpulseoccupancy/(sampletime_ms*10.0); // Integer percentage 0=>100
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\end{verbatim}
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this command is 2K bytes added.
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The concentration post is simply too much, even by itself. The math is too expensive. It’s 7K bytes about. There must be a cheaper way to do the math. Is there a pow alternative (pow gets the exponent, it appears)…
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https://stackoverflow.com/questions/101439/the-most-efficient-way-to-implement-an-integer-based-power-function-powint-int
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seems hopeful. Simple enough.
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Now I have:
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\begin{verbatim}
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if ((millis()-starttime) > sampletime_ms)//if the sample time == 30s
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{
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ratio = lowpulseoccupancy/(sampletime_ms*10.0); // Integer percentage 0=>100
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//concentration = 1.1*powf(ratio,3)-3.8*powf(ratio,2)+520*ratio+0.62; // using spec sheet curve
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concentration = 1.1*ipow(ratio,3)-3.8*ipow(ratio,2)+520*ratio+0.62; // using spec sheet curve
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//Serial.print(lowpulseoccupancy);
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//Serial.print(",");
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//Serial.print(ratio);
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//Serial.print(",");
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//Serial.println(concentration);
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lowpulseoccupancy = 0;
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starttime = millis();
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}
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\end{verbatim}
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Using a leaner integer pow, instead of a float exponent formula.
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Not sure how it will effect the data, but we will see. And it builds.
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\textcolor{green!60!blue!70}{
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\subsection{Power Dissipation}}
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As far as the power dissipation of the linear vreg… I have a lm7805 on there, with a 12V regulator. In Troubleshooting Analog Circuits, Bob Pease mentions the 5 second rule for heat – if you can hold your finger (or thumb) on it for five seconds without being burned, it’s about 85 deg C, and OK. If it’s hotter, then you have issues. Well, I am right on the line, possibly a little under 5 seconds. I could improve with a 7-9V AC Adapter, or a DC – DC switching regulator, but for now – this will do. I should mention, I’m touching the PCB opposite the LM7805 due to the construction. I should add more vias on the bottom of the vreg, also, to get more copper heatsinking.
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\textcolor{green!60!blue!70}{
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\subsection{Network Errors due to lack of Memory}}
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After installing everything, I found that the device was not working longer than a few minutes, due to memory constraints. Will need to use a larger TI part... Or just move to Arduino and use a Mega. Based on what happened here my two options are: 1) Give up on TI and use a more vetted part 2) Continue with Launchpad, using a custom PCB for the chip (instead of a launchpad that will be discontinued), and hopefully the memory issues will be resolved.
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I'm leaning towards \#1, as I wish only to monitor dust, not to be stuck in microcontroller details.
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\end{document}
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