EE 476: Laboratory 1

Introduction to the lab hardware/software.

Introduction.

This assignment introduces you to the software and hardware development tools you will use this semester to work with the Atmel AT90-series microcontroller chips.

modified Feb 2, 1999 (in red below)

Hardware

The hardware you will be using to support the AT90-series is the Flash MCU evaluation board, a small board providing:

• A target AT90-series microcontroller (mcu) with onboard flash program memory.
• A programmer for the target flash memory, including a serial connection to a PC.
• Eight general pushbuttons, eight LEDs and a RESET button.
• A serial connection for applications.
• Connectors for bringing out the microcontroller signals to user-designed peripheral equipment. Note that there is no protection on these lines. You are connecting directly to the mcu. Prudent design suggests you might want to use buffers when you are uncertain of voltage levels or other conditions. The pin definitions for the connectors are shown below. The G represents ground. The inner squares represent pins. The outer border is a white line surrounding the plug.

  

A small power supply provides power to the development board.

Most lab exercises will involve using a prototype board. A separate power supply will be used for powering the prototype board.

Software

Software you will use consists of:

• The AVR assembler which takes assembler source code and produces an object file, a hex file and a listing file.
• AVR Studio which simulates the execution of an object file.
• AvrProg which downloads the hex file to the target mcu.

1. Make sure the evaluation board is connected to power and to the PC as specified in the Evaluation Board description. Turn on the power supply with the little blue switch on the board. The LED D144 should come on and the red-yellow-green LEDs should come on, but extinguish again within a second. For this first lab, there should be jumpers from PortB to the LED connector and from PortD to the switch connector. Ask your instructor for help if these are not installed.

2. Make a subdirectory for your group in the c:\users directory. Be sure to put all your files there and to back up daily to floppy. Random user files found outside the c:\users directory may be erased.

3. The software you will use can be found in the Start menu under AVR Tools.

4. You can use the AVR assembler source-editor window to construct a text file of assembler code. For now, paste this source code into the editor window. Be sure that you have placed the 1200def.inc header information in your directory and modify the include line in the assembler source so that the assembler can find it.

5. Click on the assemble button on the assembler menu. A message window will open to tell you if there are errors in the code. If there are errors, The open the listing file to see where they are.

6. Open AvrProg, but note that the prgram will fail to open if the target board is not attached and turned on. Use the Browse button to locate the hex file you have just produced with the assembler, then click the "Program Flash" button. The code should download and start to run. Pushing ARESET on the development board will restart the program on the target mcu. This demo program should cause the LEDs to count up at 10 per second.

All timing must be done with interrupt-driven hardware timers and not with software wait-loops. Each of the following modifications should be saved separately for demonstration.

1. For the program you were given, check the clock rate by timing enough cycles of 0-to-255 to show a difference from the rate you would calculate from the interrupt time. Probably six cycles is enough.

2. Modify the program you were given to count up at one count per second only when switch0 is pressed and held. The LED displayed count should stop counting when the switch is not pressed.

3. Modify the program to cause the LEDs 0-6 to count up in binary from 00H to 07FH and back down to 00H again, and repeat indefinitely. The count rate should be 10 per second. LED 7 should blink at a rate of one per second.

Your written lab report should include:

• How accurate was the interrupt time base in the program you were given? How could you make it more accurate?
• Why did we make you use interrupts rather than wait-loops?
• The listings of your programs.

December 1998 Cornell university 1999