The Rusty Spike

A Railroad Fan's Website

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LED And Resistor Combinations Quick Reference

I got tired of continuously calculating resistor values for various low-voltage applications (Launchpad, USB power, Batteries, etc), so I put together a Quick Reference Chart. To use: If you want about 20mA through an LED, the LED has a listed Voltage Drop (Forward Bias) of 2.8V, and you have a 4.5V supply (3x AA Batteries), then your appropriate resistor value is 85 Ω

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Uploading a CSS Project to a TI Launchpad Board

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  1. Import a project into CCS.
  2. Select the root of the project. Screen should look similar to: CSS_WITH_IMPORTED_PROJECT
  3. Connect a TI Launchpad to your computer via USB.
  4. On the ‘Run’ Menu, select ‘Debug’. (note: Hitting F11 on the keyboard performs the same function)
    Run_Menu_Debug
  5. You may see a pop up window talking about ‘Low Power Modes’. It is okay to check ‘Do Not Display This Again’ and then ‘Proceed’.
  6. CCS will now shift over to the ‘Debug Perspective’ and should look like this:Debug_screen
  7. At this point, your code has been uploaded onto the Launchpad and code execution has commenced, but has been paused on the first line of the ‘main’ method. Press F8 to unpause.
  8. Find the red square in the ‘Debug’ tab of the ‘Debug Perspective’ and click it. (It should be on the upper left of the CSS window.) This stops the debugger and releases the Launchpad board to operate without the need of the computer.StopDebugger
  9. Since your code has been uploaded, you can unplug your Launchpad from your computer and use it wherever you plan to use it.

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Importing a Project into CCS

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  1. Download a project. Here’s one in a ZIP file that you can right-click and download: PoliceLightbar-Rev3.1.zip
  2. Unzip the downloaded file in your Code Composer Studio’s workspace.
  3. Launch Code Composer Studio.
  4. There are many ways to import a project. Here is the way I do it: On the File Menu, select ‘Import…’
    ImportMenu
  5. On the Import Screen unroll the ‘Code Composer Studio’ group and select ‘Existing CCS Eclipse Projects’. Click Next.
    ImportScreen
  6. Click the ‘Browse’ Button. Find your way to CCS’s workspace and select the project’s folder.
    ImportScreen2
  7. Properly selected project should result in a import screen that looks similar to:
    ImportScreen3
  8. Click ‘Finish’.
  9. The resultant CCS screen should now look similar to: CSS_WITH_IMPORTED_PROJECT
  10. Congrats! You’ve imported a project into CCS!

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Getting Code Composer Studio

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Code Composer Studio(CCS) is the Interactive Development Environment(IDE) you will need for creating and/or uploading software onto your TI board. While there are a few choices when it comes to IDEs, CCS is the ‘standardized’ IDE for the Launchpad For Model Railroaders (LP4MRR) initiative.

CCS can be obtained here:

http://processors.wiki.ti.com/index.php/Download_CCS#Code_Composer_Studio_Version_5_Downloads

You will likely have to fill out a form explaining why you are worthy of downloading TI’s software. Don’t sweat it. Just fill out the info and make sure you don’t use CCS for commercial purposes (without paying TI their due, anyways).

Installing is a snap on windows and is just the same as installing nearly any other piece of software.

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Basic Electricity 101: American Wire Gauge Chart

gauge Diameter Inches X-Section (in2) Diameter mm X-Section (mm2) Ohms per 1000 ft Ohms per km Maximum amps for chassis wiring Maximum amps for power transmission
OOOO 0.46 0.166196 11.684 107.222966 0.0490 0.16072 380 302
OOO 0.4096 0.131772 10.40384 85.014313 0.0618 0.20270 328 239
OO 0.3648 0.104524 9.26592 67.434449 0.0779 0.25551 283 190
0 0.3249 0.082909 8.25246 53.489874 0.0983 0.32242 245 150
1 0.2893 0.065736 7.34822 42.410073 0.1239 0.40639 211 119
2 0.2576 0.052119 6.54304 33.625122 0.1563 0.51266 181 94
3 0.2294 0.041332 5.82676 26.666068 0.197 0.64616 158 75
4 0.2043 0.032782 5.18922 21.149928 0.2485 0.81508 135 60
5 0.1819 0.025988 4.62026 16.766312 0.3133 1.02762 118 47
6 0.162 0.020613 4.1148 13.298485 0.3951 1.29593 101 37
7 0.1443 0.016355 3.66522 10.551272 0.4982 1.63410 89 30
8 0.1285 0.012969 3.2639 8.367166 0.6282 2.06050 73 24
9 0.1144 0.010279 2.90576 6.631690 0.7921 2.59809 64 19
10 0.1019 0.008156 2.58826 5.261633 0.9989 3.27639 55 15
11 0.0907 0.006461 2.30378 4.168566 1.26 4.1328 47 12
12 0.0808 0.005128 2.05232 3.308224 1.588 5.20864 41 9.3
13 0.072 0.004072 1.8288 2.626861 2.003 6.56984 35 7.4
14 0.0641 0.003227 1.62814 2.082036 2.525 8.282 32 5.9
15 0.0571 0.002561 1.45034 1.652131 3.184 10.44352 28 4.7
16 0.0508 0.002027 1.29032 1.307674 4.016 13.17248 22 3.7
17 0.0453 0.001612 1.15062 1.039845 5.064 16.60992 19 2.90
18 0.0403 0.001276 1.02362 0.822967 6.385 20.9428 16 2.3
19 0.0359 0.001012 0.91186 0.653072 8.051 26.40728 14 1.8
20 0.032 0.000804 0.8128 0.518886 10.15 33.292 11 1.5
21 0.0285 0.000638 0.7239 0.411587 12.8 41.984 9 1.2
22 0.0254 0.000507 0.64516 0.326919 16.14 52.9392 7 0.92
23 0.0226 0.000401 0.57404 0.258815 20.36 66.7808 4.7 0.729
24 0.0201 0.000317 0.51054 0.204722 25.67 84.1976 3.5 0.577
25 0.0179 0.000252 0.45466 0.162360 32.37 106.1736 2.7 0.457
26 0.0159 0.000199 0.40386 0.128105 40.81 133.8568 2.2 0.361
27 0.0142 0.000158 0.36068 0.102176 51.47 168.8216 1.70 0.288
28 0.0126 0.000125 0.32004 0.080448 64.9 212.872 1.4 0.226
29 0.0113 0.000100 0.28702 0.064704 81.83 268.4024 1.2 0.182
30 0.01 0.000079 0.254 0.050672 103.2 338.496 0.86 0.142
31 0.0089 0.000062 0.22606 0.040138 130.1 426.728 0.7 0.113
32 0.008 0.000050 0.2032 0.032430 164.1 538.248 0.53 0.091