Standalone Atmega328 without Arduino bootloader

In the previous post we saw how to program the Arduino bootloader on a standalone Atmega328, while in another post we saw how to upload the sketch to the microcontroller with Arduino bootloader on board.
In this post I want to highlight what I believe is the ultimate goal of the projects prototyped with Arduino: program the ATmega328 without a bootloader, so that our programs can completely override the flash of the microcontroller.
But why do we do it? The main advantages are the immediate execution of our program when the Atmega power on, and more space for our programs in the memory of the microcontroller. The disadvantage is the fact that it is no longer possible to program via simple serial (less than reload the bootloader), but we must use a dedicated programmer (or a ArduinoISP) and the time to upload the sketch is a lot longer. I advise you to use this mode only on finished project, while using the Arduino bootloader when we are debugging our programs (with continuous uploads).
But we come to practice. The programming is implemented in the same way as the previous post, with a slight modification. We need to edit the usual file “boards.txt”, and add the line xxxxxxx.upload.using = arduino: arduinoisp in the configuration of the board that we are interested in programming, where xxxxxxx is the name of the board. We make a practical example, lets take the configuration to be included in boards.txt we saw the last time for the Atmega at 8MHz: with this new addition would thus become:

##############################################################

atmega328bb.name=ATmega328 on a breadboard (8 MHz internal clock)

atmega328bb.upload.protocol=stk500
atmega328bb.upload.maximum_size=32768
atmega328bb.upload.speed=57600
atmega328bb.upload.using=arduino:arduinoisp

atmega328bb.bootloader.low_fuses=0xE2
atmega328bb.bootloader.high_fuses=0xDA
atmega328bb.bootloader.extended_fuses=0x05
atmega328bb.bootloader.path=arduino:atmega
atmega328bb.bootloader.file=ATmegaBOOT_168_atmega328_pro_8MHz.hex
atmega328bb.bootloader.unlock_bits=0x3F
atmega328bb.bootloader.lock_bits=0x0F

atmega328bb.build.mcu=atmega328p
atmega328bb.build.f_cpu=8000000L
atmega328bb.build.core=arduino:arduino

##############################################################

With this addition, we specify that the upload of the sketch does not have to end up on our Arduino UNO, but on the Atmega we want to program.
Also note the change (optional) atmega328bb.upload.maximum_size whose value becomes 32768. Basically it is the maximum space in bytes available to load our sketch. There is no longer the bootloader so the freed space is available to us.

1 – We upload by the IDE (version 0022) the example sketch ArduinoISP on our Arduino UNO
2 – We turn off everything and then connect a 22uF capacitor between RESET and GND of the Arduino UNO
3 – We Connect pin 10 of Arduino UNO to the RESET pin of the Atmega and pins 11,12,13 to pins 17,18,19 of the microcontroller (or pins 11,12,13 of another Arduino board) as shown in Figure :

4 – We do upload the sketch using the traditional command File -> Upload to I / O board

And that’s it … We programmed the microcontroller to work standalone without Arduino bootloader and without (or almost) external components.
As you can see it is very simple and allows us not only to program the ATmega328 standalone, but also a full Arduino board.
For example I use this system with the Arduino Mini Pro. These are budget boards, which have nearly all the features of the Arduino UNO, but they are very small. Usually, instead of using a standalone Atmega328 within a well-defined project, I use these small boards, and once everything is ready to be canned, I upload the sketch bypassing the bootloader, in particular to make faster ignition.
The Arduino Pro Mini is produced by Sparkfun and is available in 3.3V or 5V and with ATmega168 or ATmega328. I would recommend if the sketch does not exceed 16kB to use the ATmega168 and the 8Mhz version at 3.3V especially if your project is running on battery because it consumes a lot less.
Obviously during programming we have to select the corresponding tab from the list of boards, for example Arduino Pro or Pro Mini (5V, 16 MHz) w / ATmega168.
But the fun does not stop there …
With this system we can also program the ATtiny, the younger brothers of the Atmega. There are several versions but the most interesting are the 8-pin ATtiny85 and the 20-pin ATtiny2313. They have the advantage that consume very little power, are smaller and cheaper.
The ATtiny85 has only 5 I/O, but for many projects is just fine, considering the cost of about € 2.50 in Italy.
Moreover working with internal clock to 1Mhz consumption is really very low, and the size is like that of a NE555.
Can u think how many projects we can simplify using the ATtiny. Even only for example a PWM control of a LED strip, which would usually require operational, capacitors, NE555, and so on, with a simple ATtiny85, a potentiometer, a transistor, a few other components and 2 lines of code, the game is done…
In the next post then!

Advertisements

Loading bootloader on standalone Arduino – Arduino UNO ISP

In the previous post we saw how to program an Arduino in standalone mode.
One of the requirements was that the bootloader was already preloaded.
But if we had a virgin Atmega328, or if we wanted to program our micro to be used without an external oscillator, what should we do?
If you already have an AVR programmer, it is very simple, and I will not describe here, partly because not everyone has this accessory.
So let’s see how to use our Arduino UNO as ISP programmer.
Is said that with the UNO is not possible but in reality with a little trick, you can bypass the problem.
Do not be discouraged if there are synchronization problems while uploading the bootloader, for every problem there is a solution … but let us see the procedure.
First, I highly recommend you use the 0022 version of Arduino IDE. With version 1.0, I was able to upload occasionally and with difficulty.
I would therefore advise to keep the two installations of the software installed. In un folder the 1.0 and in another the 0022. Both can coexist without giving discomfort with each other.
Then open the 0022 IDE to load the sample file sketch “ArduinoISP“. This example allows you to transform our board in an AVR programmer. Once the file uploaded we can connect our UNO according to the following scheme:

We must then connect as shown, pin 10 of the UNO to RESET pin of the Atmega, and pins 11, 12, 13 to pin 17, 18, 19 of the microcontroller (or pin 11, 12, 13 of another Arduino board ).
In this scheme is not shown, but before we go further we must connect a 22uF capacitor between GND pin and RESET pin in the Arduino board, otherwise during the upload will take place an autoreset and the IDE will give you a sync error.
At this point we can safely select the menu Tools -> Board -> Arduino Duemilanove or Nano w / ATmega328 and launch Burn Bootloader -> w / Arduino as ISP and if everything is done correctly we should have our bootloader loaded on the microcontroller , ready to be programmed via serial as shown in the previous post. Our Arduino UNO however, could be reprogrammed normally (remember to remove the capacitor previously inserted).
Obviously we can not just load the bootloader on an standalone Arduino or on breadboard, but also on another Arduino UNO, 2009, Mini, etc..
But what if you wanted to program the board with minimal configuration without external oscillator?
The procedure is slightly different because in default IDE Boards there isn’t a configuration of this type.
We should manually add the following configuration in the file boards.txt which is located in the “Arduino” folder (under hardware\arduino):

##############################################################

atmega328bb.name=ATmega328 on a breadboard (8 MHz internal clock)

atmega328bb.upload.protocol=stk500
atmega328bb.upload.maximum_size=30720
atmega328bb.upload.speed=57600

atmega328bb.bootloader.low_fuses=0xE2
atmega328bb.bootloader.high_fuses=0xDA
atmega328bb.bootloader.extended_fuses=0x05
atmega328bb.bootloader.path=arduino:atmega
atmega328bb.bootloader.file=ATmegaBOOT_168_atmega328_pro_8MHz.hex
atmega328bb.bootloader.unlock_bits=0x3F
atmega328bb.bootloader.lock_bits=0x0F

atmega328bb.build.mcu=atmega328p
atmega328bb.build.f_cpu=8000000L
atmega328bb.build.core=arduino:arduino

##############################################################

At this point we have a scheme like the following:

Always remember to place 22uF capacitor between GND and RESET, and verify that the sketch ArduinoISP is loaded on our board.
At this point we can load the bootloader by selecting Tools -> Board -> ATmega328 on a breadboard (8 MHz internal clock)
If all goes well, we should have our ATmega328 with Arduino bootloader loaded and running at 8MHz. In this way we can feed our final circuit with 3.3V (if you want), allowing a lower consumption of our project.
If the upload at 16Mhz is successful and that at 8MHz no, it’s because the first upload of 8MHz bootloader needs to be done with the circuit still configured with external crystal, because if we remove the external oscillator, the circuit is not is able to communicate with the ISP programmer. Successively any further loading can be done without the external oscillator circuit.
And here I advance a gem that will be the subject of our next post. If I have finished my project and then I no longer need to use the Arduino bootloader (because I do not need to upload via serial – see previous post), I can upload the sketch directly into Atmega328 memory, overwriting the bootloader. And to do that I have to just use the same connections as seen above …
But for now we stop and we will continue to talk about in the next post.

Arduino Standalone (Arduino without Arduino)

In this post I will show how to use Arduino in a standalone configuration, ie use the ATmega328 (equipped with a bootloader) in circuit without having to lug around all our Arduino Uno (or the board you have).
The concept is this: I have finished protyping my project with Arduino (such as a RGB Led Lamp) and I’m ready to make the final version of the lamp.
You could you use the Arduino board, but it would be inconvenient not just from the point of view of cost, but also from the point of view of size and consumption … In reality, what we need is just the microcontroller with bootloader and a few external components.
If our Atmega has no bootloader, we need to load it, but first things first … Let us assume that when we already have the bootloader onboard.
To be able to upload the sketch we have to use the connections as shown in the figure:

It important to remove the microcontroller from the board with which we are going to program, otherwise we will program that instead of our Atmega standalone.
As you can see the connections are very simple, you just connect power, TX and RX pins and RESET pin.
At this point from our Arduino IDE we can go to upload the sketch, of course, after selecting “Arduino Duemilanove or Nano w / ATmega328” from the Tools -> Board. And that’s it.
Of course, the same would apply if the Atmega is programmed to work with the 8Mhz internal oscillator. With the difference that we didn’t need the two capacitors and the crystal shown in the figure. To use the internal oscillator, however, we should re-program the bootloader (as we shall see in the next post).
If we have available (and I recommend you to buy it because it is a cheap and really usuful accessory) a USB / Serial converter like the Sparkfun FTDI Basic or Ardino USB-Serial Light, connections would as the following:

It’s nothing complicated, just the connections are almost as before: VCC, GND, RX, TX, while the reset is a bit different because it requires a 100nF capacitor between the pin DTR (or RTS – not to be confused with RST) and Atmega RST.
We have seen how to program a standalone ATmega328 with bootloader preinstalled, in the next post we will see how to load the bootloader on a virgin Atmega328 in both versions: with external 16mhz crystal, and with internal 8Mhz oscillator.

Arduino and ATmega328: A bit of clarity

Until a few weeks ago,  I didn’t know exactly what was the difference between Arduino and its “core” Atmega328.
I read here and there that the Atmega328 can work in stand-alone, with or without the Arduino bootloader, and even in its minimal configuration, without any external components.
I was so confused about what exactely is Arduino and the ATmega328 “without Arduino”, as they have not much information on the Internet.
Eventually, with a lot of patience, “munching” here and some information on various blogs, reading magazines and books, and doing field trials, I finally came on the bulb (or LED) in my head and all appeared more clearly.
So I decided to publish this post where I explain briefly and simpy (and probably not in a totally professional way – I would ask apologize if there are any inaccuracies) what is Arduino and what sets it apart from the Atmega328 (which is included in last generation Arduino boards).
If I had to define the Arduino project, i can say that Arduino is an open source hardware & software platform which allows you to use more quickly and easily the potential offered by the microcontroller ATmega328.
The hardware part, is typically represented by the boards listed on the official website, with lots of open schemes that allow us to realize by ourself the various Arduino boards or modify and customize them to our liking. The software part is instead represented by the often quoted bootloader, libraries and by the IDE interface that allows you to program and debug our Arduino board.
But what are the differences between Arduino and its ATmega328 microcontroller and what are the advantages in microcontroller programming?
From the perspective of hardware, the Arduino board (for example Arduino UNO) is ready for use: it has everything we need to program the microcontroller just plugging the board into the USB port of the PC: it has on board an internal power connector, a USB port, a processor that acts as a USB / Serial converter, a power LED, a status LED connected to pin 13, two LEDs indicating TX / RX, female strip header for connection of  I / O ports and of course our ATmega328 microcontroller with Arduino bootloader already loaded.
In this way, opening the IDE and selecting the serial port of the PC we can load our sketch with a button and in a few seconds (typically 2-3). The upload is done via the serial port emulated by USB, which is connected to the TX and RX pin of the Atmega (pins respectively 3 and 2).
From the point of view of the software, the bootloader preloaded on Atmega (whether that is mounted on an Arduino board or just on a breadboard), is what allows serial communication with our PC. Without the bootloader to load the sketch (our “programs”), we would need an AVR programmer, more expensive, a bit ‘more cumbersome to use and slower to load the sketch. The bootloader is therefore a program, a firmware might say, whose job is basically to upload our sketch compiled into the flash memory of the microcontroller via serial communication, making sure that this program is not going to overwrite the memory area where bootloader resides. So when we upload a sketch we’re going to write in a zone of free memory and the bootloader is not affected and remain intact.
The main advantage compared to Atmega without bootloader, as we have seen, is that it can be uploaded via a simple serial communication, and at a faster rate than that which we directly loading the sketch using AVR programmer.
In addition to the bootloader, we have included libraries in the Arduino IDE. These libraries add many functions and constants that make it possible to greatly simplify the code we are going to write making it much more usable than the standard microcontroller. All this is managed through the IDE, which is the Arduino interface in which we write the sketchs, we upload and debug.

That said (hoping not to have bored and to be able explain without creating further confusion) in the next post we will see how to build a stand-alone Arduino, and how to program the ATmega328 without a bootloader, solution that sometimes could be advantageous.