Nuts and Volts - September 2011

SMILEY’S WORKSHOP ☺

We test the code by intentionally sending scripts with errors. When we click on each error macro, we see the output shown in Figure 2. Note that the third line shows that the first command was handled correctly since it has no errors. Further note that the ‘Sixth test, no terminator’ macro results in nothing showing on the Receive Text box since the command_line_demo has no way of knowing that we think we have sent it a valid script. So, it sits spinning its wheels waiting for the TERMINATOR character (hint — it isn’t a former governor of California). This is not a rigorous validation of the code. For one thing, it won’t catch improper use of the SEPARATOR and TERMINATOR characters, but it is certainly good enough for now. If you find a problem, well, you’ve got the source code.

If we want to convert the demo to a real application like the robot pick and drop we mentioned above, we would modify the COMMANDS array as shown next:

const CMDS COMMANDS[] PROGMEM = {
{“UP”,move_up},
{“DOWN”,move_down},
{“LEFT”,move_left},
{“RIGHT”,move_right},
{“PICKUP”,close_gripper},
{“DROP”,open_gripper},
{“HELP”,help},
{0,NULL}
}

■ FIGURE 2. Catching script errors.

buy my C Programming book, Butterfly projects kit, and the Virtual Serial Port Cookbook from the Nuts & Volts shop mentioned previously. NV

We would write the indicated functions: move_up(), move_down(), move_left(), move_right(), close_gripper(), and open_gripper(). Now, all you have to do is call them with a command-line script. Simple, huh? Well, I think so, and you are going to see this thing a lot in the coming months where I’ll use it for lots of software and hardware micro machinations.

Questions? As usual, if you want to be helpful when you find a problem or have a question, you’ll need to put on your biohazard suit and start a thread on www.avrfreaks.net with the word ‘avrtoolbox’ in the title. This way, I’ll probably see it. (First, read my blog entry that will tell you why you need the biohazard suit: http://smiley micros.com/blog/2011/01/24/using- an-internet-forum.)

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Cana Kit

www.canakit.com

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USB-LOGIC

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DSO-NANO-V2

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ASSEMBLED

Next month, I think we are going to take a look at digital input and output, so stay tuned and find out. If you just can’t wait and want to get a leg up on all this serial stuff and real C programming for the AVR (while helping support your favorite magazine and technical writer), then