The BPI-UNO Arduino Uno is a microcontroller board based on the ATmega328 (datasheet). It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz crystal oscillator, a USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started.

=Main spec=
*ATmega328P @16 MHz.
*32 KB Flash.
*2 KB SRAM.
*1 KB EEPROM

There is a self-restoring fuse on the bpi-uno that automatically disconnects the power supply when short-circuiting or overcurrent exceeds 500mA, thus protecting the USB port and bpi-uno of the computer. While most computer USB ports provide internal protection, this fuse provides additional protection.

==Power==

BPI-NANO can power with MicroUSB port,PH2.0 port and VIN port.

Power dependent pins are as follows:
*PH2.0 port: can input 7-12V,It can be controlled by a power switch。
*5V:5V power PIN。when use USB power,direct output USB supplied 5V voltage;When using external power supply, output 5V voltage after voltage stabilization压。
*3V3:3.3V power output PIN。output Max is 50 mA。
*VIN:Connect to external dc 5V power supply
*REF:I/O reference voltage. Other devices can identify the development board I/O reference voltage through this pin。

Note:FT232RL will only work if it is powered through the USB port。

==Input and Output==
Each of the 14 digital pins on the BPI-UNO can be used as an input or output, using pinMode(), digitalWrite(), and digitalRead() functions. They operate at 5 volts. Each pin can provide or receive a maximum of 40 mA and has an internal pull-up resistor (disconnected by default) of 20-50 kOhms. In addition, some pins have specialized functions: Serial: 0 (RX) and 1 (TX). Used to receive (RX) and transmit (TX) TTL serial data. These pins are connected to the corresponding pins of the FTDI USB-to-TTL Serial chip. External Interrupts: 2 and 3. These pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value. See the attachInterrupt() function for details.

Some of them have special functions and these pins are as follows:
*Serial:0(RX)、1(TX),Used to receive (RX) and transmit (TX) TTL serial data. These pins are connected to the corresponding pins of the FTDI USB-to-TTL Serial chip。
*xternal Interrupts: 2 and 3. These pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value
*PWM output:BPI-NANO have 3, 5, 6, 9, 10, and 11. Provide 8-bit PWM output with the analogWrite() function.
*SPI:10(SS)、11(MOSI)、12(MISO)、13(SCK),These pins support SPI communication, which, although provided by the underlying hardware, is not currently included in the Arduino language。
*L13:There is a built-in LED connected to digital pin 13. When the pin is HIGH value, the LED is on, when the pin is LOW, it's off.。
*I2C: 4 (SDA) and 5 (SCL). Support I2C (TWI) communication using the Wire library (documentation on the Wiring website).

BPI-NANO have 6 analog inputs, each of which provide 10 bits of resolution (i.e. 1024 different values). By default they measure from ground to 5 volts, though is it possible to change the upper end of their range using the analogReference() function. Additionally, some pins have specialized functionality:

There are a couple of other pins on the board:
*REF:Reference voltage for the analog inputs. Used with analogReference().
*Rst:Bring this line LOW to reset the microcontroller. Typically used to add a reset button to shields which block the one on the board.

==LED==

BPI-UNO arduino UNO have 4 LED,The effects are as follows:
*ON:Power indicator.When the...

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