In this lesson you are going to construct a Metromini/Arduino Uno on your breadboard. The advantage of building a the Arduino on a breadboard is that:
- It costs less. The Metro Mini costs $12.50. The parts to build this device cost under $3.00. This is important if you are building a permanent project and don’t need features such as on-board USB, a voltage regulator and reset button.
- It is more configurable: Using breadboard version of the device, you can easily change the power supply from 1.8V to 5.0V. You can also easily change the clock speed from a slow 32.768 real time clock pulse to a fast 20Mhz.
Above is a diagram of the Metro Mini broken down into functional groups of components. Below is a description of each of these groups. For these devices the name used on your breadboard schematic is included.
- USB Converter. This section of the board is responsible for converting the USB signal from the computer to a pair of serial signals that can be used by the microcontroller.
- Power Conversion: This section of the board is responsible for providing direct power from the USB as well as regulated power for 5V and 3.3V.
- LEDs: This section includes LEDs and their resistors which are used to indicate power on the board and whether data is being sent to or from the device.
- Microcontroller: This is a surface mount version of the ATMega328p, which is the microcontroller that you program. (IC1)
- Clock: This is the crystal clock resonator that used to provide the correct timing “heartbeat” for your controller. (Y1)
- Reset: The reset button is used to reset the code on the controller back to the beginning. It is useful if the code gets stuck in a bad state. (S1)
- Filter: This is a capacitor that is being used to filter or clean the power supply against voltage spikes. (C2)
- Pullup: This is a resistor that is used to prevent the microcontroller from going into the reset state. (R2)
You will now build a working version of the Metromini or Arduino Uno using individual components and on a breadboard. Below are the components you need to collect. You will only need one of each.
| Item | Image |
| ATMega328p microcontroller |  |
| 16Mhz Resonator |  |
| .1uF Capacitor |  |
| 4.7K Resistor |  |
| Momentary switch |  |
The following is the basic microcontroller circuit. Carefully construct this circuit on your breadboard. Make sure to use short wires for your all your connections. Neatness counts! Important: The numbers on the IC1 correspond to order of the pins on the actual IC. All ICs start their pin counts at 1 under a notch or divit. The counting always continues in a counterclockwise direction around the IC. An example is below.
| Name | Description |
| IC1 | The ATMega328p At |
| Y1 | The crystal clock resonator |
| C2 | The filter capacitor |
| R2 | The pullup resistor |
TEACHER CHECK ____