= Arduino Programming Techniques =

This is mostly gonna be C++

== Accessing a GPIO line ==

{{{
    //data direction register bit
    unsigned char *portDDRB;
    
    portDDRB = (unsigned char *) 0x24;
  }}}

First we get an 8bit pointer and load it with a hard coded value of 
the data-space address for that register

See [[arduino_nano#Pins]]

== Bit masks ==

{{{
    #define BIT6_MASK 0x40 // 0100 0000
    #define BIT5_MASK 0x20 // 0010 0000
    
    *register_pointer = (*regiser_pointer) & (~BIT6_MASK);
    *register_pointer = (*regiser_pointer) | BIT5_MASK;

  }}}
  
For the first one we find the compilemnt then '&' it with the current 
register values, which will only flip the selected bit.

For the second one we '|' it with the contents, setting a 1 in the 5th position

== Polling GPIO pins ==

repeatedly reading the value of the input pins and comparing the current value
to the previously-read value to determine if an external signal event has
occurred. 

We can do this by comparing the last known value of the gpio pin with the
current one

See [[arduino_nano#Pins]]


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