Build your own Arduino on a breadboard using the ATmega8L-8PU and flash an LED

Step 1: Hardware Preparation

1.ATMEGA8L-8PU avr microcontroller (Figure 1)

figure 1

2. USBasp (a tool for burning bootloader) (Figure 2, top)

3. USB to TTL serial cable (I use the FT232 chip, which has better stability and is used to load programs under Arduino) (Figure 2 below)

figure 2

4. 16M crystal, breadboard, LED, etc., and some Dupont cables

There may be a question here: Why is ATMEGA8L-8PU equipped with a 16M crystal oscillator?

The reason is this: in principle, the ATMEGA8L-8PU uses a maximum 8M crystal oscillator, but the bootloader of the M8 platform used in Arduino is compiled based on ATMEGA8 and uses a 16M crystal oscillator; I don't have an ATMEGA8 chip (note that the chip I use has an "L" at the end), and I don't know how to recompile the bootloader, so I have to equip the existing ATMEGA8L with 16M. Although it is "overclocked", no problems have been found in the current experiment.

Step 2: Software preparation (download from Baidu)

  1.arduino的IDE：arduino-1.0.5-r2

  2. USB asp driver and serial port line driver (please note that you need to download the driver for the chip corresponding to your serial port line)

  3. progisp (this is the software used to burn the bootloader)

Note: After installing USB asp, you must copy the two files libusb0.dll and libusb0.sys in the driver directory to the directory where the burning tool progisp.exe is located. In particular, there are multiple sets of libusb0.dll and libusb0.sys files in the driver file directory of USBasp, and you must choose the file that corresponds to your computer system.

For example, Figure 3 is the x64 driver directory. My computer is x64win7 with AMD CPU, and the two files I copied are under amd64. Of course, the computer with Intel CPU uses the two files in the ia64 folder.

Figure 3

Otherwise, the following problems may occur when burning the program:

Figure 4

Step 3: Build a Minimum System on a Breadboard

Wiring as shown in Figure 5

Figure 5

Actual example Figure 6:

Figure 6

Step 4: Use usbasp to burn the bootloader

After installing and connecting the USBasp driver, open the progisp software as shown in Figure 7

Figure 7

1. Select the chip as ATmega8

2. Open the HEX file of the bootloader, which is located in the Arduino IDE software's arduino-1.0.5-r2hardwarearduinobootloadersatmega8 directory. The file name is ATmegaBOOT-prod-firmware-2009-11-07.hex

3. Configure the fuse bit to 0xCADF. Note that incorrect fuse bit configuration may lock the chip.

4. Check the Program Fuse checkbox

5. Click the automatic button to start programming the chip. After programming is completed, the word "successfully" will appear in the box in the lower left corner of the software.

Step 5: Create the Flashing LED Code in Arduino IDE

/*

  Blink

  Turns on an LED on for one second, then off for one second, repeatedly.

  This example code is in the public domain.

 */

// Pin 13 has an LED connected on most Arduino boards.

// give it a name:

int led = 13;

// the setup routine runs once when you press reset:

void setup() {                

  // initialize the digital pin as an output.

  pinMode(led, OUTPUT);     

}

// the loop routine runs over and over again forever:

void loop() {

  digitalWrite(led, HIGH);   // turn the LED on (HIGH is the voltage level)

  delay(1000);               // wait for a second

  digitalWrite(led, LOW);    // turn the LED off by making the voltage LOW

  delay(1000);               // wait for a second

}

Figure 8

After entering the code, click the first "check mark" button in the IDE shown in Figure 8 to compile.

Step 6: Load the compiled program into the Atmega8 chip under Arduino IDE

1. Disconnect any connection between USBasp and the breadboard (this is important, otherwise the download will fail. Of course, if the bootloader is downloaded correctly, you can use USB to TTL to download Arduino programs in the future, and USBasp will not be needed).

2. Connect the VCC and GND of USB to TTL to the corresponding pins of Atmega8L chip. Connect the TXD of USB to TTL to the RXD of ATmega8L, and the RXD of USB to TTL to the TXD of ATmega8L, refer to Figure 6.

3 Connect a light-emitting diode on the breadboard: the positive pole of the light-emitting diode is connected to PB5 (pin 19) of ATmega8L, and the negative pole is connected to GND through a current-limiting resistor (about 500 ohms). (Refer to Figure 10, the current-limiting resistor is not connected in Figure 10)

4. Connect USB to TTL to PC. Then in Arduino IDE, click the menu selection Tool->Board->Arduino NG or older /W ATmega8, and then select Tool->Board->Serial Port and select the COM port corresponding to USB to TTL on your computer. See Figure 9.

Fig. 9

Fig.10

5. Finally, click the "→" button on the Ardunio IDE to start loading the program. At the same time, use a DuPont line to short-circuit the RST (first pin) of Atmega8L with GND on the breadboard to reset it (of course, it is most convenient to connect a button), and then wait for the download to complete.

6. After the download is complete: you can see the experimental results. The LED light turns on for one second, turns off for one second, and so on. If this is successful, it means that the bootloader correctly guides the download and operation of the program, and the Ardunio program itself is also correct.

Fig.11

At this point, a minimal Arduino development board has been made, and the first Arduino introductory program has been run. The implementation of subsequent Arduino programs and system expansion are up to everyone.

Figure: The correspondence between the PIN pins in Arduino and the pins of the Atmega8L chip.

Additional information:

There is a board type configuration file boards.txt in the installation directory arduino-1.0.5-r2hardwarearduino of Ardunio IDE. Some of the configuration codes are as follows

##############################################################

atmega8.name=Arduino NG or older w/ ATmega8

atmega8.upload.protocol=arduino

atmega8.upload.maximum_size=7168

atmega8.upload.speed=19200

atmega8.bootloader.low_fuses=0xdf

atmega8.bootloader.high_fuses=0xca

atmega8.bootloader.path=atmega8

atmega8.bootloader.file=ATmegaBOOT-prod-firmware-2009-11-07.hex

atmega8.bootloader.unlock_bits=0x3F

atmega8.bootloader.lock_bits=0x0F

atmega8.build.mcu=atmega8

atmega8.build.f_cpu=16000000L

atmega8.build.core=arduino

atmega8.build.variant=standard

##############################################################

Here you can see the configuration of the fuse bits, the crystal oscillator frequency, and the HEX file of the specified bootloader. This is why the fuse bits are configured as shown in the fourth step and the crystal oscillator must be selected as 16M.