Transcript micro
http://students.iitk.ac.in/roboclub
MICRO-CONTROLLER:
A microcontroller is the brain of the robot:
These are:
1.
Integrated Circuits (ICs)
Programmable – You can define what they do.
This is what makes them different from other simpler
ICs, such as AND gates, inverters, etc
Logic tables relating Input and Output can be defined
by you
Many useful features built in to the uC itself
2.
3.
ATMEGA 16
16 KB Flash Memory…
40 pin UC…
32 I/O Pins
These pins have other functions like UART, ADC, SPI,
LCD, Interrupt, TIMERS, etc…
But we will now focus on I/O and TIMER…
Maximum Voltage 5V, current rating about 10 milliamperes
Atmega8
I/O Pins:
Setting Data Direction (I/O?): DDRX
Register
PORTX Register
PINX Register
I/O Registers
Input / Output is controlled through special
variables called “registers”.
Registers are actual hardware memory locations
inside the μCs with predefined names and sizes.
Assigning a value to these registers in the
program changes the corresponding hardware
configuration. And, these values can be altered
multiple number of time at any point in the
program.
There are 3 registers that control the I/O pins:
DDR, PORT and PIN.
Each port has it’s own registers. Hence, DDRA,
PORTA, PINA registers for port A; DDRB,
PORTB, PINB for port B and likewise.
DDR(Data Direction Register)
Decides whether the pin is Input or Output.
DDR is an 8 bit register. Each bit corresponds to a
particular pin on the associated port.
If a bit on the DDR register is 0, then the
corresponding pin on the associated port is set as
input.
Similarly, if the bit is 1, then the pin is set as output.
If a pin is configured as input, then it has some
floating voltage unless an external voltage is
applied.
For an output pin, the voltage is fixed to a particular
value.
Setting Register Values
MSB of DDRA
corresponds to the
pin A7.
If DDRA = 0b10010110,
then:
PORT register
PORT is also an 8 bit register. The bits on the
PORT register correspond to the pins of the
associated port in the same manner as in the
case of the DDR register.
PORT is used to set the output value.
If the pin is set as output, then a PORT value of
1 will set voltage at that pin to 5V, and PORT
value 0 sets the voltage to 0V.
If the pin is configured as an input, PORT value
serves the purpose of pull up or pull down.
PIN register
PIN is a register whose value can be
read, but cannot be changed inside the
program.
It gives the value of the actual voltage at
a particular pin. 1, if the value at the
required pinis 5V and 0 for 0V.
Summary
Tools Required -> CVAVR
Compiler -> CVAVR
The code is written in C language so we
need to convert it into the format that
Atmega understands .
Transfer code to Atmega AVR
Studio
Avr Programmer
So we need two softwares overall
a) CVAVR –> Editor and Compiler
b) Avr Studio –> Transfer Code to Atmega
While & For
While (conditon) { … ... }
for(initialisation; condition; increment)
{……}
Lets Begin by blinking a simple
LED
How to program a microcontroller:
A microcontroller understands only binary language (0
and 1)…We write the code in C language in CVAVR
(Compiler + IDE).
We compile the code to generate the .hex file (which
the machine understands)
We transfer the .hex file to Atmega using a
Programmer
Hardware: Serial Programmer, STK
500, USB etc… (Contains chips to
convert voltage levels and protocols)
Software: AVR Studio, AVRDUDE,
etc…
Programmer Pin connection with Atmega 8
How to Run Motors through UC?
The Atmega16 has a current rating of 5-10
mA.
The normal DC motor’s current ratings
start from 150 mA and above.
So the motor cannot be directly attached
to the Atmega, hence a motor-driver is
used… (eg: L293, L298, etc…)
TIMERS:
Atmega has:
Timer 0, 8 bit (OC0 at PB3)
Timer 1, 16 bit (2 parts A and B each of 8 bit, OC1A
at PD5, OC1B at PD4)
Timer 2, 8 bit (OC2 at PD7)
There are 2 clocks:
System Clock (fs)
Timer Clock (ft = fs or fs/8 or fs/64 or ….)
(For generating 38 KHz in TSOP Sensors)
(For MOTORS)
NOW LET US HAVE A
LOOK AT CVAVR AND AVR
STUDIO AND HOW TO
PRACTICALLY PROGRAM AN
ATMEGA 16
THANK YOU