= Arduino Nano =

A very small arduino product, better for hobby embedding 

see [[arduino_techniques|Programming Techniques]]

== Features ==

* ATMEL AVR ATmega328P microcontroller
* 8 bit @16Mhz
* 2Kbytes SRAM 
* 32Kbytes flash
* 1Kbytes EEPROM
* Three on board LED's * 20 IO pins
* 6 PWM and 6 ADC

== Notes ==

* WHEN UPLOADING BE SURE TO SET BOARD TO ATMEGA328OLD
 - this is the atmega328old for BOARD_SUB in the makefile

=== Memory ===

* AVR instructions are 16 or 32bits wide, therefore the flash is 16K x 16
* EEPROM has endurance of ~10000 write cycles
* Program counter is 14 bits wide
* First 32 memory locations (0x0000 - 0x001F) are registers
* Next 64 registers are standard IO (0x0020 - 0x005F)
* Next 160 are extended IO (0x0060 - 0x00FF)
* Everything else is SRAM (0x0100 - 0x08FF)

=== IO ===

* GPIO pins
* Have a Data Direction Register (DDR)
  - Sets if data should go in or out
* Is kept up via a [[multiplexer]] to decide which bit

=== Pins ===

Pins are controller by the atmega's ports. Each port has different port
registers. Each bit of the 8 bit register controls a single pin. Port D
controls pins 0 through 7, C controls the analog pins, and B controls 8 through
13

* PortC
  - Port C data regiser
  - 0x28
  - R/W 8bits
* DDRC
  - Port C data direction register
  - 0x27
  - R/W 8bits
* PINC
  - Port C input pints address
  - 0x26
  - R 8bits
* PortB
  - Port B data register
  - 0x25
  - R/W 8bits
* DDRB
  - Port B data direction register
  - 0x24
  - R/W 8bits
* PINB
  - Port B Input pins address
  - 0x23
  - R 8bit

Same pattern:
* PortD
  - 0x2B - 0x29

=== Interrupts ===

Interrupts are the same as OS typical interrupts, controlled by the Interrupt
lookup table. On this device the ILT is instead a control register. 

[[embedded]]