Adafruit sure loves the ATmega328, they use them a lot for their own projects. The processor has plenty of GPIO, Analog inputs, hardware UART SPI and I2C, timers and PWM galore - just enough for most simple projects. When they need to go small, they use a Pro Trinket 3V or 5V, but when size isn't as much of a concern, and an USB-serial converter is required, we reach for an Adafruit METRO.
This is the Adafruit METRO with headers. It comes with headers soldered on. It's a fully assembled and tested board with SMT headers attached as well as through hole headers. If you don't want a Metro with through-hole headers or at least, holes for them, but not attached for super-slimness, check out their Metro without Headers.
METRO is the culmination of years of playing with AVRs: Adafruit wanted to make a development board that is easy to use and is hacker friendly. At the heart is an ATmega328P, with 32KB of flash and 2KB of RAM, running at 16 MHz
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Power the METRO with 7-9V polarity protected DC or the micro USB connector to any 5V USB source. The 2.1mm DC jack has an on/off switch next to it so you can turn off your setup easily. The METRO will automagically switch between USB and DC.
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METRO has 19 GPIO pins, 6 of which are Analog in as well, and 2 of which are reserved for the USB-serial converter. There's also 6 PWMs available on 3 timers (1 x 16-bit, 2 x 8-bit). There's a hardware SPI port, hardware I2C port and hardware UART to USB. Logic level is 5V but by cutting and soldering closed a jumper, you can easily convert it to 3.3V logic
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USB to Serial converter, there's a hardware USB to Serial converter that can be used by any computer to listen/send data to the METRO, and can also be used to launch and update code via the bootloader
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Four indicator LEDs, on the front edge of the PCB, for easy debugging. One green power LED, two RX/TX LEDs for the UART, and a red LED connected to pin PB5
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Easy reprogramming, comes pre-loaded with the Optiboot bootloader, which is supported by avrdude and only uses 512 bytes.
- Works with all Adafruit shields!
We also include 4 rubber bumpers to keep it from slipping off your desk. Metro shown with their 12x capacitive touch shield attached just to demonstrate the headers, but that shield is not included!
Don't forget to grab & install the FTDI VCP drivers from FTDI to make the COM/Serial port show up right!
Technical Details
Detailed specifications:
- ATmega328 microcontroller with Optiboot (UNO) Bootloader
- USB Programming and debugging via the well-supported genuine CP2104
- Input voltage: 7-9V (a 9VDC power supply is recommended)
- 5V regulator can supply peak ~800mA as long as the die temp of the regulator does not exceed 150*C
- 3.3V regulator can supply peak ~150mA as long as the die temp of the regulator does not exceed 150*C
- 5V logic with 3.3V compatible inputs, can be converted to 3.3V logic operation
- 20 Digital I/O Pins: 6 are also PWM outputs and 6 are also Analog Inputs
- 6-pin ICSP Header for reprogramming
- 32KB Flash Memory - 0.5K for bootloader, 31.5KB available after bootloading
- 16MHz Clock Speed
- Compatible with "Classic" and "R3" Shields
- Adafruit Black PCB with gold plate on pads
- 53mm x 71mm / 2.1" x 2.8"
- Height (w/ barrel jack): 13mm / 0.5"
- Weight: 19g
- Derivative of "Arduino UNO R3 Reference design"
- Open source hardware files on github!
Revision History:
- As of August 31, 2015 we have updated the Metro's headers to be slightly taller so that they are the same height as classic 'non-SMT' headers for a better shield-fit
- As of Oct 12, 2017 we now have fully thru-hole headers instead of SMT headers.
- As of March 30, 2018 we now have swapped the FTDI chip for a SiLabs CP2104
