Файл: C Programming for microcontrollers (Joe Pardue, 2005).pdf

Chapter 2: Quick Start Guide

Software

We will use three FREE software packages, the WinAVR compiler from sourceforge.net, the AVRStudio 4 from ATMEL, and Br@y++’s Terminal.

WinAVR – Oh, Whenever…

WinAVR is a set of tools for C programming the AVR microcontroller family. A bunch of folks have volunteered their time to write this software and give it away as part of the free software movement (www.sourceforge.net). These folks generously giving there time to help others is almost enough to change my cynical opinion of humanity. You can spend thousands on C compilers for microcontrollers and before WinAVR you had to spend several hundred even for a crappy compiler. This software is FREE, but SourceForge has expenses so send them some money at www.sourceforge.net/donate.

At http://sourceforge.net/projects/winavr/ you see the summary:

“WinAVR (pronounced "whenever") is a suite of executable, open source software development tools for the ATMEL AVR series of RISC microprocessors hosted on the Windows platform. Includes the GNU GCC compiler for C and C++.”

Go to: http://winavr.sourceforge.net/index.html and check out their homepage.

But don’t get too distracted with all that yet, just use the tools as shown here, and once you reach the end of this book, then you’ll have the skills to fully exploit those web sites.

Programmers Notepad

We’ll be writing our software using the most excellent Programmers Notepad, another FREE program available at sourceforge.net and included in the WinAVR distribution package. Imagine what Microsoft would charge for this FREE software. Be a good guy or gal and send them some money at http://www.pnotepad.org.

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Chapter 2: Quick Start Guide

AVRStudio – FREE and darn well worth it.

AVR Studio is provided free by the good folks at ATMEL Corporation, who seem to understand that the more help they give developers, the more they will sell their microcontrollers. Actually, this too could cost hundreds and still be darn well worth it, but unless you just really like Norway, don’t send them any money, they’ll get theirs on the backend when you start buying thousands of AVRs for your next great invention.

The AVR Studio will be used for two things: first, to download your software to the AVR Butterfly, and second, to simulate the ATMEGA169 running your software.

Br@y++ Terminal:

The original Quick Start Guide chapter used HyperTerminal, which is hard to setup, clunky, and hated by so many folks on the AVRFreaks.net forum that I contacted Br@y++ and he gave me permission to use and distribute his highly recommended and easy to use and understand terminal package. You can get it at http://bray.velenje.cx/avr/terminal or http://www.smileymicros.com. It is shown in Figure 7: Bray's Terminal. The examples in the text still show the HyperTerminal, but it shouldn’t be a problem substituting Bray’s. If you want to use HyperTerminal, the introduction to it is in Appendix 1.

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Hardware

Constructing Your Development Platform

ADC

USART

USI

PORTB

Pin 2

Figure 2: The Butterfly front

Solder the female headers to the ADC, PORTB, and PORTD lands. Note that the square pads are pin1 and that PORTB and PORTD seem to have 10 pins, but they don’t, pins 9 and 10 are ground and power respectively (see Figure 2).

The RS-232 Connection:

Communication with the PC requires three lines: TXD, RXD, and GND. The TXD is the transmit line (data from the PC to the Butterfly), RXD is the receive line (data from the microcontroller to the PC) and GND is the common ground. Notice that there is a bit of relativity in this equation, the microcontroller’s RXD wire is the PC’s TXD wire and vice versa. I can’t count the number of times I’ve

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Chapter 2: Quick Start Guide

done stupid things like connecting the microcontroller’s RXD pin to the DB-9 RXD pin, because I didn’t think ‘RXD – receive - relative to what?’

The parts list has a DB-9 female solder cup RS-232 connector. Follow the illustrations in Figure 3.

USART (J406) connector: pin1 RXD

USART (J406) connector: pin2 TXD

USART (J406) connector: pin3 GND

Solder cup backside pin 5 - GND

Solder cup backside pin 3 - TXD

Solder cup backside pin 2 - RXD

Figure 3: RS-232 connections.

NOTICE HOW THE RXD AND TXD LINES CROSS OVER – PAY CAREFUL ATTENTION AS IT IS EASY TO GET THESE REVERSED.

Constructing the power supply:

The Butterfly comes with a CR2450 coin battery that will power the LCD for a long time, but will be used up quickly by the RS-232 connection and our experiments. Remove the coin battery and construct a battery pack with parts from the JAMECO parts list (Appendix 7) using the following pictures. Be sure and get the power, red wire, and ground, black wire, correct: as shown in Figure 4 and Figure 5.

NOTE: ALL THE ILLUSTRATIONS SHOW PORTD WITH AN 8-PIN HEADER AND THE POWER WIRES SOLDERED IN PLACE. THE PARTS KIT SPECIFIES 10-PIN CONNECTORS FOR BOTH PORTS B AND D. USE THE 10-PIN HEADER ON PORTD AND INSERT RATHER THAN SOLDER THE POWER WIRES.

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Chapter 2: Quick Start Guide

Figure 4: Battery holder, switch, and batteries.

Figure 5: External battery connection to Butterfly

A few days after making the power supply I left it on all night, so I added an LED (Figure 4) to the switch so that I’d know that it was on. You can solder the long leg of an LED to the rightmost pin on the switch, where the +3v goes to the Butterfly, and then solder a 330 resistor to the short leg and the resistor to the rivet at the base of the battery on the right. The LED is lit when the switch is to +3V.

Test your Connection using Brays Terminal:

Hook your RS-232 cable to the Butterfly as in Figure 6. The run Bray’s Terminal, (well, Br@y++’s to be exact – available at http://bray.velenje.cx/avr/terminal and http://www.smileymicros.com) and configure it as in Figure 7 with the radio buttons set to select your COM port, 19200 Baud rate, 8 Data bits, parity of none, 1 Stop bits, and no handshaking. Click the connect button. Turn on your Butterfly

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power supply, then with the joystick button centered press it and watch the stream of ?????? question marks that should be coming from the Butterfly. This is the Bootloader telling you that it is alive and ready to be boot loaded, or perhaps it is just curious as to what’s going on?

Figure 6: Butterfly hooked up to RS-232

Figure 7: Bray's Terminal

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If you don’t get the string of question marks, then try the other COM ports (in Figure 7 only COM1 and COM3 are shown for my machine, yours may be different. Press disconnect then connect and try again. If it still doesn’t work, carefully check that the RS-232 cable is connected. Try again. Still no? Recheck that you’ve got the DB-9 soldered correctly to your Butterfly. Try again. Still no? Is it turned on? If you move the joystick upward do you get the LCD scrolling message? Yes? Turn it off and on and press the center again. Still no? If its not working by this point go back and meticulously retry everything you can think of, including passing a dead chicken over the setup while chanting voodoo hymns. It took me a while to get all this running and I supposedly know what I’m doing, so don’t feel bad if this is a little harder than you might hope. (You get what you pay for).

In a moment you will scoop out the Butterfly’s brains, toss them aside, and stick in some brains that Igor got from a garage sale, so let’s do one final test on the Butterfly as it came out of the package. If all goes well, you will eventually be able to reload the Butterfly’s original brains, but all seldom goes will, as Igor will readily attest.

With the Butterfly hooked up to the RS-232 port and the Br@y++ Terminal running, turn the Butterfly on and click the joystick up to get the LCD scrolling. Move the joystick straight down three times till you see ‘Name’ then move the joystick to the right twice till you see ‘Enter name’ then move the joystick straight down once and you will see ‘Download name’ then push down the joystick center for a moment until you see ‘Waiting for input’. Now write a name in the bottom text panel of the Br@y++ Terminal (Figure 8) and hit enter (or push it gently if you prefer). The name you entered should be scrolling across the LCD as shown in Figure 6.

Use this gray window to send characters to the Butterfly, not the white one above.

Figure 8: Enter name to send to the Butterfly

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Let’s Blink Some LED’s:

Figure 9: Blinky wiring diagram and photo of wired board

All the parts are listed in the JAMECO parts list Appendix 1. Put the LEDs in the breadboard with the short leg on the resistor side. Use the 330-Ohm resistors to jumper to the ground strip. You’ll need to make a bunch of jumper wires, cut 9 pieces about 4 inches long strip each end about 3/8 inch, and connect them to the breadboard as shown in Figure 9, with the right most LED connected to pin 1 of PORTD (Figure 2) and subsequent pins connected sequentially. The pins are numbered with the odd pins on the bottom of the PORTD land and the even pins on the top. Cut a 6” wire and use it to connect the ground strip to the ground pin of PORTB as shown.

Now connect your RS-232 cable between the computer and the RS-232 connector you soldered to the Butterfly. Your hardware should look like Figure 10.

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Chapter 2: Quick Start Guide

Figure 10: Hardware setup for Blinky.

Blinking LEDs – Your First C Program

You might wonder why blinking an LED is the first project, when traditional C programming texts start with the classic “Hello, world” program. It certainly seems that since the Butterfly has an LCD that can show the words it would be easy. But the reality is that controlling the LCD is much more complex than blinking an LED, so we’ll save the LCD for later when we’ve gotten a better handle on things.

•Make a directory called Blinky for this project.

•Copy ‘…/WinAVR/Samples/makefile’ (notice that it has no extension) to the Blinky directory.

Write it in Programmers Notepad

• Find Programmers Notepad that was installed as part of WinAVR (you should have an icon for it on your desktop) and open it. You will need to add a tool, which will let you use the AVR Studio simulator.

•Open the Tools menu and click on Options.

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•In the Options window select Tools:

•Then select Add:

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•Change the check box to look like:

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Chapter 2: Quick Start Guide

•Click OK.

•Click File, then New, then C/C++, and name it Blinky.c.

•Save in Blinky directory and CAREFULLY TYPE exactly as shown:

// Blinky.c

#include <avr/io.h> #include <avr/delay.h>

int main (void)

{

// set PORTD for output DDRD = 0xFF;

while(1) {

for(int i = 1; i <= 128; i = i*2)

{

PORTD = i; _delay_loop_2(30000);

}

for(int i = 128; i > 1; i -= i/2)

{

PORTD = i; _delay_loop_2(30000);

}

}

return 1;

}

•Open File and again save ‘Blinky.c’ to your Blinky directory

•NOTE: YOU MUST ADD THE EXTENSION ‘.c’ TO THE NAME

•Open the file ‘makefile’ in your Blinky directory.

•Change these lines:

MCU = atmega128

# Output format. (can be srec, ihex, binary) FORMAT = ihex

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# Target file name (without extension). TARGET = main

•To:

MCU = atmega169

#Output format. (can be srec, ihex, binary) FORMAT = ihex

#Target file name (without extension). TARGET = Blinky

•Close and save changes to makefile to the Blinky directory.

•Open Tools and click [WinAVR] Make All to make your Blinky.hex file

•Open Tools and click [WinAVR] Make Extcoff to make your Blinky_coff file.

Download to the Butterfly with AVRStudio

• Find AVR Studio (you should have an icon for it on your desktop) and open it.

•In the File menu Open ‘…\Blinky\Blinky.cof

•Select the AVR Simulator and the ATMEGA169 as:

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•Select Finish

•DO NOT try to run the simulation; the delay loop will take forever to run. We’ll use the simulator later.

•Turn the Butterfly off.

•Press and hold down the joystick button.

•Back to the AVR Studio, open the Tools menu and WHILE HOLDING DOWN THE JOYSTICK BUTTON click the AVR Prog menu item. Then wait until you see:

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•Release the joystick button. Your finger hurts doesn’t it? Enter Blinky.hex in the ‘Hex file’ box. Press the program button and the program should magically flow from your PC into the AVR Butterfly Flash memory.

•AVR Prog will say: Erasing Programming Verifying OK.

•WHEN YOU WANT TO DOWNLOAD A DIFFERENT HEX FILE, DON’T FORGET TO CHANGE THE HEX FILE NAME. DON’T SAY I DIDN’T WARN YOU AFTER YOU WASTE TIME SCRATCHING YOUR HEAD OVER WHY YOUR NEW PROGRAM SEEMS TO RUN EXACTLY LIKE THE LAST ONE YOU DOWNLOADED. I make this mistake a lot.

•If instead of the above window you get:

•Go back a few steps and try again. You probably left Bray’s Terminal running so it has locked the port. Then maybe not.

Blinky Goes Live

•Turn the power supply off and then back on, the LCD will be blank, click the joystick up (maybe a couple of times) and:

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•Your LEDs should be making like a Cylon with the light bouncing back and forth. If you don’t know what a Cylon is, try Googling Battlestar Galactica, not that I’m recommending the series, but the bad guys had great eyes:

Figure 11: From the cover of the Battlestar Galactica comic Red Cylon.

When you compiled Blinky.c you may have suspected that a lot of stuff was going on in the background, and you would have been right. The compiler does a lot of things, and fortunately for us, we don’t really need to know how it does what it

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