In previous post, I show a simple programming example of INT0. As it's already stated, the Atmega16 has up to 3 external interrupt sources. In this example, I use all its external interrupt sources, the INT0, the INT1, and the INT2.
I select the low logic level of these interrupt source to trigger the ISR. Whenever any interrupt occurs, its corresponding output LEDs will toggle its logic state. The output LEDs are PB5, PB6, and PB7.
ATMega16 is
an 8-bit microcontroller built using RISC architecture bases on flash
technology. Its original manufacture Atmel, now become a part of the
Microchip Technology since 2016. However those AVR microcontroller
series are still continuous to develop.
The ATMega16 in DIP and SMD Package
ATMega16 has three storage memory parts:
Flash memory, or program memory for program storage (firmware) of 16 kBytes with ISP feature.
1 kBytes of general purpose registers
512 Bytes of SRAM
The CPU could clock up to 16 MHz when it’s supplied about 5 V, yield the executing speed 16 MIPS.
It comes with 40-pin DIP version and also a SMD version.
Microcontroller communication interfaces built inside this device:
Digital input output (I/O) is divided into four 8-bit ports:
PORTA
PORTB
PORTC
PORTD
Pin Diagram of the most common used ATMega16 40-Pin DIP Package
They are bi-directional read/write port register.
Analog input channels are multiplexed with those digital I/O. The
Analog to Digital Converter (ADC) yields an 10-bit resolution available
between its 8 input channels. The ADC gain is select-able.
Analog output, Pulse Width Modulation (PWM) modules generate an
analog output voltage via their output compare pins. They work with the
three timer modules inside this MCU.
Interrupt is a effective way to notifies the MCU. In ATMega32 the
interrupts are the external interrupt and the peripheral interrupts
triggered by its inside peripheral modules.
Programming the ATMega16 AVR
The assembly language is design with the target MCU with the
description of the internal hardware operations. Currently most the
8-bit MCU is programmed using the C language targeting a specific
architecture.
Atmel (now becomes a part Microchip Technology) develop and IDE,
Atmel Studio enable the programmer the code their AVR and AVR32 products
for free. It bases on the AVR GCC. However this IDE supports the
assembly, C and C++ programming languages. Now, in 2020 the current
version is Atmel Studio 7.
I know a few third party compiler for the AVR MCU series:
MikroC for AVR
CodeVision AVR
IAR Embedded Workbench for AVR
Some of them offer a free version of their compiler with a limit
coding. But for a full features access of the resources the programmers
need to pay for a license.
For me I prefer Atmel Studio for my programming and project developments.
Getting Started With Atmel Studio 7
The Atmel Studio support both a low level and a high level C/C++
coding. For most programmers, they like to program in C due to its ease
of coding density.
To get start the programmer need to download the Atmel Studio IDE
from the Microchip Technology website, and install it on their PC.
After the installation, open the IDE and make a new project.
Make a new project
Select GCC Executable Project, its location and name
Select the ATMega16 as a target device
Then coding window will appeared.
Let write a sample code as shown in this picture. This code blink PORTB of the ATMega16.
Now it’s ready to build the project
An error-free coding creates the binary file for the target MCU to execute.
AVR C source code in Atmel Studio 7:
/*
* m16_blink.c
*
* Created: 10/10/2020 7:39:16 PM
* Author : Admin
*/
#include <avr/io.h>
#define F_CPU 16000000UL
#include <util/delay.h>
int main(void)
{
//PORTB AS OUTPUT
DDRB=0xFF;
while (1)
{
PORTB=0x00; //Clear PORTB
_delay_ms(1000);//Wait For 1000 mS
PORTB=0xFF; //Set PORTB
_delay_ms(1000);//Wait For 1000mS
}
}
Within the code above the label F_CPU is a parameter used by the delay.h file below the delay is created.
The schematic below is full assembling symbol for the breadboard system assembling.
Schematic diagram for this example to wire on the breadboard
The Hardware Test
Development Board and ISP Programmer
I use my own development board
I designed/assembled. The code is written to fit this board. However,
it doesn’t come with a pre-burned boot-loader nor an on-board block of
ISP. I putted an ISP header, compatible to the USBasp USB-based ISP programmer. The USBasp is open-source. We can make it by hand, or buying from any store for a few Dollars.
Getting Started With C In Atmel Studio 7 Using ATMega16
I also made my own one using the ATMega8 with a dozen of components.
The host PC side ISP software is widely available. I have been using
many software that the USBasp ISP hardware. Currently, I switched to a
GUI version of AVRdude. This software supports many ISP hardware for the Microchip AVR devices.
The AVRdude
As mentioned earlier, the AVRdude has a user-friendly GUI version that made by an author.
A GUI version of the AVRdude
For a first use of the USBasp ISP programmer, the user need to
install the USB driver of this USB programmer. Previously, I used
Windows 7 32-bit OS. Installing the USBasp driver on this OS is easy
because the driver file comes with downloaded zip file from the USBasp
website.
Currently, I migrate my computer’s OS to Windows 7 64-bit and up to
Windows 10 64-bit. Installing the USB driver with those conventional
driver file is very hard, and doesn’t work for me. I saw a solution from
the online forum. It’s the Zadig, USB driver installation.
Plug your USBasp to the host PC operates the Windows7/10 64-bit, and
install the USB driver with an appropriate one’s. Then open the AVRdude
to test the device reading/writing.
A successful writing to the ATMega16
After this successful hex file uploading let see the real hardware test.
A program test on development board
Click here to download this example. To get started coding the ATMega16 using C in Atmel Studio 7, see this video.
The development board for any microcontroller are widely available
especially in the online market place. They come with various peripheral
device and programming examples.
The Atmel (Now Microchip) AVR microcontroller is one of the most
popular microcontroller in-use today. The development boards for this
device are available. They are ready to use with a select-able scale and
price.
The final test of the board with error free
For an electronic hobbyist or student, a development could be built
using a single board PCB with a minimum on-board peripheral devices.
Using a development board, the prototyping and testing are safer and
time saving.
With a PCB fabrication service support, I decided to design a development board for the Atmel AVR ATMega16 microcontroller for my own microcontroller experiments.
Features
The design comes with many features that fully work with the ATMega16 chip:
Digital inputs and outputs
analog input devices
Display
RS-232
SPI peripheral device
TWI peripheral devices etc.
It mentions only the ATMega16 chip. However, the board supports other
AVR devices with the 40-pin DIP package. I have tested this board with
some chips I posses:
ATMega16
ATMega32
ATMega644
I think it works with the ATMega1284. But currently I don’t have this chip in my own laboratory.
The PCB Design
The completed design made with a free EDA software. It takes almost a week to finish the schematic and PCB design.
The finished design of this development board
The schematic design need up to two letter size sheet.
Schematic Sheet2
Schematic Sheet1
Within the design most of the resistors and the capacitors are in the
SMD package. The PCB size is a little bigger than 10 cm square. I didn’t
plan about the target of the PCB.
Top Layer
Bottom Layer
Within the design most of the resistors and the capacitors are in the
SMD package. The PCB size is a little bigger than 10 cm square. I didn’t
plan about the target of the PCB.
On Board Resource
Beside the DC power supply circuit, all other components have their own unique function connect to the microcontroller.
This board is just ready after a few hours of the assembling/soldering.
DC Regulated Power Supply
An AC to DC converter is need to power this board. All on-board
component supplies from a +5V regulated IC – AMS1117-5.0. There is an
optional +3.3V regulated IC – AMS1117-3.3 that could be useful for
others low voltage devices.
The power supply circuit
Microcontroller Clock And Reset Circuit
The on-board ATMega16 chip supplies at +5V DC. Clock and reset circuit are already wired with this chip on board.
Reset and Clock for the ATMega16
An external crystal clock for the ATMega16A has a maximum value of 16 MHz.
In System Programming
The in System Programming (ISP) is an appropriate flash memory upload
tool for the Microchip AVR chip. Currently, most of the ISP programmers
are very low cost as a result of the open-source tool.
ISP header for this ATMega16 development board – It follows the USBasp programming header.
This header is a 10-pin IDC header/connector. It fits the USBasp programmer that connects externally.
RS-232
The RS-232 communicate between a host PC with the on-board
microcontroller. This communication could be very classic now. The
recent development replaces this interface with a USB-Serial converter
chip. This new technology is very effective in cost and size.
The RS-232 circuit – The Tx/Rx of the host PC side will connect to the on-board microcontroller across a DIP switch.
However I still have the HIN232/MAX232 RS232 level converter that still has a few left in my workshop.
Digital Input/Output
The basic digital input/output on this board made of two distinct ports. PORTB is for output that connects to a 8-bit LED.
A DIP switch enables or disables the output to LED
Port A accepts the digital input from a DIP switch. The switch has only a ground connection when it’s on.
PORTA connects to a DIP switch. When it’s on a low logic value is created.
All digital input pins of the ATMega16 have their own weak pull-up resistor that will be turn on by software.
Multiplexed Display
A multiplexed display created by a numbers of seven-segments LED
displays. Each digit of the multiplexed display shares the same
segments. Each common of the display turns on and off the digit.
A six-digits multiplexed display. Two distinct DIP swith enables and disables the connection to the microcontroller.
The display in-use here is a 0.36″ common cathode display. PORTB
connects the segments across a DIP switch while PORTC controls the
six-digits common of the seven-segments. The SW8 DIP switch has a two
remaining pins, allowing the user to configure the voltage reference
pins for the microcontroller’s ADC.
Analog to Digital Converter
The Analog to Digital Converter (ADC) module built inside the
ATMega16 chip. PORTA is multiplexed with the ADC inputs – ADC0 to ADC7.
Two ADC inputs – The LM35DZ and a trim POT
On this board I put only two analog input devices – The LM35DZ analog temperature converter and the trim POT.
External Interrupts
The external interrupts of the ATMega16 creates by three distinct pins, name INT0, INT1 and INT2.
External interrupt mechanism
A typical tactile switch creates an interrupt to the microcontroller.
On this board it happens at the low logic level of the input.
Character LCD
A character LCD developed by Hitachi has been popular for a few decades. It still in-use now for education purpose.
The Hitachi HD44780 character LCD interfaces in 4-bit mode.
Serial Peripheral Interface
The Serial Peripheral Interface (SPI) of the ATMega16 chip here
connects to a 12-bit Digital to Analog Converter (DAC) across a DIP
switch. The preset analog voltage reference of the DAC chip is to +5V.
The MCP4922 dual 12-bit DAC connects to the ATMega16 SPI
The analog output voltage of these two DAC connect to the outside world via a male header block.
Two-wire Serial Communication
The Two-wire serial communication (TWI) originally known as the
Inter-integrated Circuit (I2C) requires only two electrical
communication lines on a single bus to command and exchange the data. On
this board I put two TWI chips – a DS1307 Real Time Clock (RTC) and an
AT24C16 EEPROM.
The TWI communication interface to the ATMega16
A DIP switch SW5 allows the connection between the TWI block and the
microcontroller. Optionally this gate is bridge between the RS-232 and
the microcontroller.
Connectors And Headers
This board allow an external connection to the outside device via
many pre-soldered connectors/headers. The main ATMega16 chip with its
40-pin wires to a 2×20 on-board male header. Other headers are,
The DC power supplies outputs – +12V, +5V and +3.3V DC.
The SPI output
The TWI external connection
The USART external connection etc
They are labeled on the development board.
Ordering A PCB
As it’s often mentioned, using a service from a PCB fab gives more
advantage for a complex design circuit board. The PCB of this ATMega16
development board was ordered from PCBWay.
The company provides the PCB fabrication service up to 14 layers.
Getting the PCB delivered to my warehouse within a few days saves a lot
of time and engineering cost.
A pack of PCB from PCBWay
Unboxing the PCB #1
Unboxing the PCB #2
Soldering And Assembling
Ordering the PCB from a fabrication service gives some advantages to the students and hobbyists:
It’s easy to solder as the soldering pads are plated with some
soldering friendly materials – lead, lead free, immersion silver and up
to the hard gold. These materials are very hard to get oxidized in the
air if the PCB are kept for a long period.
The components legend
on both sides give the information to the solder man and the end user
about the components placement and about the printed circuits.
With
the advantage of solder mask the PCB is very hard to become corrosive
cause by some other chemical materials that it suffered. The solder mask
color is select-able between various colors – green, blue, yellow etc.
The green one’s is very convenient as it’s very easy for the user to
observe the tracks.
I use a 40 W electrical soldering iron to solder all the components. The
overall soldering/assembling processes take only a few hours.
A 40W gun type iron solder is suitable for this job
Electric soldering iron looks like a gun. It comes with a switch
useful for thermal recovery, or even a high temperature requirement.
Some components for soldering
A finished assembling at top layer
A finished assembling at the bottom layer
I'm writing and testing sample program for Atmega16 for this board. They are releasing gradually.
ATMega644P Programming using AVR-LibC in Microchip Studio IDE (2025)
Microchip
Studio is free of charge compiler provides by device manufacture. It
comes with the GNU AVR-LibC that's widely used by many AVR programmers.
However it only contains the standard C library functions. It has a
little peripheral libraries. We need to write our own functions to
interface with external hardware.
I
recently test this chip by programming it using C. Some examples I
tested using software simulator while others are tested using my AVR
Prototype Board.
