The Adafruit Metro Without Headers is a powerful, flexible development board designed for hobbyists, educators, and professionals alike. Based on the ATmega328 microcontroller, it is a robust platform for developing electronics projects and prototypes. With its compatibility with the Arduino Integrated Development Environment (IDE), users can easily write, upload, and run custom code, making it ideal for a wide range of applications from simple LED blinkers to more complex robotic controllers.
Explore Projects Built with Adafruit Metro Without Headers
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This circuit features an Adafruit Proto Shield R3 configured with a DS18B20 temperature sensor, a WS2812 RGB LED matrix, and an LCD I2C display. The microcontroller on the Proto Shield reads the temperature from the DS18B20 sensor and displays it on the LCD. It also controls the LED matrix to show random colors and indicates temperature status with onboard LEDs.
This circuit is a monitoring system for a subway platform, utilizing an Arduino UNO to control an RFID reader, an ultrasonic sensor, and two LEDs. The RFID reader authenticates users, and upon successful authentication, the ultrasonic sensor monitors for objects within 50 cm, triggering alerts if abnormal behavior is detected. The LEDs provide visual feedback for the system's status.
This circuit features a Raspberry Pi 4B interfaced with an IMX296 color global shutter camera, a Neo 6M GPS module, an Adafruit BMP388 barometric pressure sensor, an MPU-6050 accelerometer/gyroscope, and a Sim800l GSM module for cellular connectivity. Power management is handled by an MT3608 boost converter, which steps up the voltage from a Lipo battery, with a resettable fuse PTC and a 1N4007 diode for protection. The Adafruit Perma-Proto HAT is used for organizing connections and interfacing the sensors and modules with the Raspberry Pi via I2C and GPIO pins.
This circuit uses an Arduino Mega 2560 to read temperature data from multiple DS18B20 sensors, display the data on an ILI9341 TFT display, and maintain time using an Adafruit DS1307 RTC module. It also receives IR signals using a VS1838B IR receiver and includes an Adafruit MS8607 PHT sensor for additional environmental monitoring.
Digital I/O Pins: 20 (of which 6 provide PWM output)
Analog Input Pins: 6
DC Current per I/O Pin: 20 mA
DC Current for 3.3V Pin: 50 mA
Flash Memory: 32 KB (ATmega328) of which 0.5 KB used by bootloader
SRAM: 2 KB (ATmega328)
EEPROM: 1 KB (ATmega328)
Clock Speed: 16 MHz
Pin Configuration and Descriptions
Pin Number
Function
Description
1
RESET
Resets the microcontroller
2-7
Digital I/O
General-purpose digital input/output pins
8-13
Digital I/O
General-purpose digital input/output pins
14 (A0)
Analog Input
Analog input pin 0
15 (A1)
Analog Input
Analog input pin 1
...
...
...
19 (A5)
Analog Input
Analog input pin 5
20 (AREF)
Analog REF
Reference voltage for the analog inputs
21 (GND)
Ground
Ground
22 (RESET)
Reset
Additional reset pin
23-28
Digital I/O
General-purpose digital input/output pins
...
...
...
29 (VIN)
Voltage Input
Input voltage to the board
Note: This table is not exhaustive and only includes a selection of the available pins.
Usage Instructions
How to Use the Component in a Circuit
Powering the Board:
Connect a 7-12V power supply to the VIN and GND pins, or plug in a USB cable to provide power.
Connecting I/O:
Digital pins can be used as inputs or outputs. Set the pin mode in your code using pinMode(pin, mode);.
Analog pins are primarily used for input but can also serve as digital I/O.
Programming the Board:
Connect the board to a computer using a USB cable.
Open the Arduino IDE, select the correct board and port.
Write your sketch and upload it to the board using the IDE.
Important Considerations and Best Practices
Always ensure the power supply is within the specified limits to prevent damage.
When connecting external components, consider the current limits of the I/O pins.
Use a current-limiting resistor when connecting LEDs to digital pins.
Avoid making connections or disconnections to the board while it is powered.
Troubleshooting and FAQs
Common Issues
Board not recognized by the computer:
Check the USB cable and connections.
Ensure the correct drivers are installed.
Sketch not uploading:
Verify the correct board and port are selected in the Arduino IDE.
Press the reset button on the board just before uploading.
Unexpected behavior in circuits:
Double-check wiring and connections.
Ensure power supply is stable and within the recommended range.
FAQs
Can I use the Adafruit Metro Without Headers with Arduino shields?
Yes, it is compatible with many Arduino shields. However, since it comes without headers, you will need to solder headers or use jumper wires.
What is the difference between the Metro with headers and without headers?
The functionality is the same; the only difference is the presence of pre-soldered headers, which can be an advantage for breadboarding but may be less flexible for custom projects.
How do I reset the board?
You can reset the board by pressing the onboard reset button or by connecting the RESET pin to GND briefly.
For further assistance, consult the Adafruit forums or the extensive online community resources.
Example Code for Arduino UNO
// Blink an LED connected to pin 13
void setup() {
pinMode(13, OUTPUT); // Set pin 13 as an output
}
void loop() {
digitalWrite(13, HIGH); // Turn the LED on
delay(1000); // Wait for a second
digitalWrite(13, LOW); // Turn the LED off
delay(1000); // Wait for a second
}
Note: The Adafruit Metro Without Headers is compatible with Arduino UNO code, so this example will work as is. Ensure you have selected the correct board in the Arduino IDE before uploading.
Remember to keep your code comments concise and within the 80 character line length limit.
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