1. Programming the ATmega16
B. Furman
14SEP2010

2. Mechatronics Concept Map
User Interface
ME 106
ME 120
Power Source
Controller (Hardware & Software)
ME 106
ME 190
ME 187
Power Interface
ME 106
Signal Conditioning
ME 106
ME 120
Actuator
ME 106
ME 154
ME 157
ME 195
Sensor
ME 120
ME 297A
System to Control
ME 110
ME 136
ME 154
ME 157
ME 182
ME 189
ME 195
BJ Furman 26JAN06

3. Audience participation required!
Recap Last Lecture
Audience participation required!
Binary and hex numbers
Digital pins as inputs or outputs
Pins are bidirectional for digital I/O
DDRx (x=A, B, C, or D) register determines direction
8-bit register
a ‘1’ means
a ‘0’ means
main_RC.c
Programmer’s block
#include
Initialization function, init();
DDRA, DDRB, and uart_init() 1 2 3 4 5 6 7
Ask students regarding what the ‘big ideas’ were for each of the bullet items.
I mentioned that the lectures will highlight the important things to know in the class. Yes, try to read all the reading assignments.

4. Test Your Comprehension
Write a statement that will make all pins of PORTC to be outputs
DDRC =
DDRC = 0b ;
DDRC = 255;
Write a statement that will make pins 5, 3, and 1 of PORTC to be outputs, and the rest inputs
DDRC = 0b ;
0xFF;

5. Structure of main() Look again at main_RC.c init() printf_example()
Declaration of variables
char, string, uint8_t, uint16_t, uint32_t, double
printf()
format string
while(1)
Why?
PORTB = PINA;
Explain what is going on as a result of this statement

6. ATmega16 Port Pin Details
See the ATmega 16 data sheet, p
Port pins consist of three register (special memory location) bits:
DDRx
Data Direction bit in DDRx register (read/write)
PORTxn
PORTxn bit in PORTx data register (read/write)
PINxn
PINxn bit in PINx register (read only)

7. PORT Pin Schematic

8. ATmega16 Internal Architecture

9. ATmega16 Features

10. Make bits 5 and 3 of PORTB high and the rest low
Bit Manipulations
Examples of how to work with Port pins
Setting bits
Clearing bits
Toggling bits
Make bits 5 and 3 of PORTB high and the rest low
Challenge:
Work up the example on the board, so you can sketch out the bit positions, and talk about the operators, such as left shift ( << ) and logical OR

11. Summary of Bit Manipulation
Setting a bit (making it a ‘1’)
Bitwise OR the PORTx register with the corresponding bit mask
Ex. PORTB | = _BV(3);
Clearing a bit (making it a ‘0’)
Bitwise AND the PORTx register with the corresponding complemented bit mask
Ex. PORTB & = ~( _BV(3) );
Toggling a bit (making it flip)
Bitwise XOR the PORTx register with the corresponding bit mask
Ex. PORTB ^ = _BV(3);

12. Pull-up Resistors Pins configured as INPUTS can be ‘pulled up’ to VTG
Why is this useful?
Puts an input pin in a known state (logic high) if no external influence has pulled it down (to logic low)
Example of a switch connected between a pin and ground
How is it done?
When the pin is configured as an input, SET the corresponding bit in PORTxn
Undone by clearing the bit

13. Recap ATmega16 Digital I/O
Pins are bi-directional. Can configure as:
Inputs – _______ determines the pin voltage
Outputs – ______ determines the pin voltage
Direction determined by bits in DDRx register
Where x is A – D (and corresponds to all 8 pins associated with the port)
If configured as output:
Program can specify a pin to be high (VTG) or low (GND) by writing a corresponding 1 or 0 (respectively) to PORTx register
Ex. To make Port C pins 7, 3, and 4 low, and the rest high
PORTC=___________; (write in binary, then in hex)

14. Recap ATmega16 Digital I/O, cont.
If pins configured as input, this means:
External device can pull pin voltage high or low
i.e. take up to VTG or take down to GND
You can determine the state of the port pins by reading the PINx register
Grabs all eight logic levels at the same time
Ex. PORTA configured as inputs
PA0
PA1
PA2
PA3
PA4
PA5
PA6
PA7
VTG
unsigned char a_pins;
a_pins=PINA;
What is the content of a_pins:
binary:__________
hex:_____

15. Recap ATmega16 Digital I/O, cont.
If pins configured as input, cont.:
Can turn pull-up resistors on or off by writing a 1 or 0 to corresponding pins in PORTx
A pull-up resistor internally connects a pin to VTG to give it a defined state (logic high, i.e., 1)
Ex. Write the code that will:
Make Port A pins inputs
Turn on pull-up resistors
Read the voltages on the pins and store them in a variable, testA
What is the value of testA in binary and hex?
PA0
PA1
PA2
PA3
PA4
PA5
PA6
PA7
VTG

16. Reading PORTA Pins Example
unsigned char testA;
DDRA=0;
testA=PINA;
What is the content of testA?
binary:
hex: F9
PA0
PA1
PA2
PA3
PA4
PA5
PA6
PA7
VTG