dthUSART – C library for AVR microcontrollers (beta) and example code

I decided to create a simple C library for USART and AVR microcontrollers for the purpose of studying the USART serial interface.

This library is likely to be often updated. Open source code on my github:
https://github.com/xdth/AVR_dthUSART

Below is an example application. It will echo back strings received via serial at 9600 bit rate (defined in dthUSART.h), using the internal oscillator at 1 Mhz.
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Interfacing attiny2313 AVR with HD44780 LCD

We will use an attiny2313 AVR microcontroller to display strings on an HD44780 LCD (4-bit mode).

482 bytes of flash written. Using internal oscillator.

## Connections

+-----------------------------------+----------------+
|            HD44780 LCD            | attiny2313 MCU |
+-----------------------------------+----------------+
| PIN 1 (GND)                       |                |
| PIN 2 (+5V)                       |                |
| PIN 3 (contrast/GND)              |                |
| PIN 4 (reg select)                | PIN 2 (PD0)    |
| PIN 5 (R/W)                       | PIN 3 (PD1)    |
| PIN 6 (Enable)                    | PIN 6 (PD2)    |
| PIN 7                             |                |
| PIN 8                             |                |
| PIN 9                             |                |
| PIN 10                            |                |
| PIN 11                            | PIN 12 (PB0)   |
| PIN 12                            | PIN 13 (PB1)   |
| PIN 13                            | PIN 14 (PB2)   |
| PIN 14                            | PIN 15 (PB3)   |
| PIN 15 (220 Omhs resistor to +5V) |                |
| PIN 16 (GND)                      |                |
+-----------------------------------+----------------+

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Bit Manipulation in C

Bitwise Operators

& AND
| OR
^ XOR
~ NOT

Truth Tables

AND (“&”)

truth table

+--------+--------+-----------------+
| bit a  | bit b  | a & b (a AND b) |
+--------+--------+-----------------+
|     0  |     0  |               0 |
|     0  |     1  |               0 |
|     1  |     0  |               0 |
|     1  |     1  |               1 |
+--------+--------+-----------------+

byte example

     11001000  
   & 10111000 
     -------- 
   = 10001000

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Arduino as ISP

I prefer to develop in pure C instead of using the Arduino framework, for both learning and code size purposes. I use the Arduino board solely as an AVR programmer, using my script qAVR to flash the microcontroller.

## material
– breadboard
– jumper wires
– 10µF capacitor
– 220 ohms resistor
– LED
– Arduino
– Target microcontroller (in our example, attiny2313)

## install dev env
pacman -S avr-gcc avr-libc avrdude
wget https://raw.githubusercontent.com/xdth/qavr/master/qavr (place it in your .bin folder)

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Calculator written in C for the 555 timer IC

+5 ---+---------------+---+
      |               |   |
      R            +----------+
      |            |  8   4   |
  +---+------+-----|7        3|------/\/\/\---+------- Vout
  :          |     |  LMC555  |               |
  C to test  +-----|6         |             -----
  :                |          |             -----
ground       +-----|2        5|----+          |
             |     |    1     |    |        ground
             |     +----------+  0.1 uF
             |          |          |
   Clock ----+        ground     ground
     ^

I needed a quick calculator for the 555 chip and decided to write one in C. Enjoy.
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