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How to make an Arduino-compatible minimal board

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Posted by Nick Gammon   Australia  (19,385 posts)  [Biography] bio   Forum Administrator
Date Tue 08 May 2012 11:12 PM (UTC)  quote  ]

Amended on Thu 29 Aug 2013 06:03 AM (UTC) by Nick Gammon

Message
This page can be quickly reached from the link: http://gammon.com.au/breadboard


Make your own board


Once you have been playing with Arduinos for a while you probably are thinking that you want to deploy one, but without the expense, and physical size, of using a whole new Uno board. This post describes how to do that.


Related links




AtMega328P chip


We will start off with a "raw" Atmega328P-PU chip, the sort of thing you might buy off the shelf from Digi-Key, Element14, or other suppliers:



Note that pin 1 is at the end where there is a notch in the plastic and an extra hole on the top.

The chip itself can be purchased for around $US 3.

Anti-static precautions


To avoid "zapping" your chip avoid handling it by the legs. I sit down at a bench, and use long-nosed insulated pliers to hold the chip by the plastic part, not the legs, to avoid destroying it with a static charge.

Minimal wiring


The chip pinouts are:



The very basics are to wire +5V to VCC and AVCC (AVCC is the analog power in), plus both GND pins (normal and analog).



Connected are:


  • +5V to VCC (pin 7) (red wire)
  • GND to pin 8 (blue wire)
  • +5V to AVCC (pin 20) (red wire)
  • GND to pin 22 (blue wire)
  • Connect /RESET (pin 1) to +5V via a 10K pull-up resistor


We also add a 0.1 uF decoupling capacitor to both sides of the board. It would be better to have the capacitor right next to the chip legs, and cut those wires a bit shorter.

There is also a 10K pull-up resistor for the reset pin. Although the chip has a built-in pull-up, this appears to make it reset more reliably when downloading new programs.

There are wire links connecting the Gnd and +5V of both sides of the breadboard together.

Power supply


The chip requires around +5V power to run. It has an absolute maximum rating of 5.5V, and a minimum of 1.8V. At lower voltages not all clock speeds are available.

For running at 16 MHz you need at least 3.78V and at 8 MHz you need at least 2.40V. (Caveat: under testing I found that it did not seem to work reliably much under 2.8V at 8 MHz).

[EDIT] That unreliability would have been because of the brown-out reset kicking in at 2.7V. If you are using lower voltages you need to adjust or disable the brown-out detection.

I am planning to run at 8 MHz using the internal oscillator, to save parts and space. Thus you could conceivably run the whole thing off 2 x 1.5V batteries, giving around 3V nominally. However 3 x 1.5V batteries would be OK, and let you run it at 16 MHz.

For now, I'll just grab power from the Uno board, while programming it, or from the FTDI connector.

Test the chip


Our next major stage is to upload a bootloader onto the chip. The bootloader simplifies subsequent programming, as it accepts programming commands from the serial port. However we need another chip that supports SPI to burn the bootloader.

So at this stage we need another board, such as a Uno, Duemilanove or so on. Now this is a bit of a "chicken and egg" situation, which is why this process is called "booting".

http://en.wikipedia.org/wiki/Bootstrapping

Grab a second board (which already has the bootloader on it) and connect up 6 wires as shown:



Wiring


Programming Uno     Target board

D10 (SS)            Reset - pin 1 (green)
D11 (MOSI)          Pin 17 (white)
D12 (MISO)          Pin 18 (orange)
D13 (SCK)           Pin 19 (black)

Gnd                 Gnd (blue)
+5V                 +5V (red)


Now grab the "board detector" sketch from here:

http://gammon.com.au/Arduino/Atmega_Board_Detector.zip

Unzip and upload that into your Uno.

When you run it you should see something like this in the Serial Monitor:

Board Detector Output


Atmega chip detector.
Entered programming mode OK.
Signature = 1E 95 0F 
Processor = ATmega328P
Flash memory size = 32768
LFuse = E2 
HFuse = DA 
EFuse = FD 
Lock byte = EF 
Bootloader in use: Yes
EEPROM preserved through erase: No
Watchdog timer always on: No
Bootloader is 2048 bytes starting at 7800

Bootloader:

7800: 0C 94 34 3C 0C 94 51 3C 0C 94 51 3C 0C 94 51 3C 
...
7FF0: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF 

MD5 sum of bootloader = 27 EB 87 14 5D 45 D4 D8 41 44 52 CE 0A 2B 8C 5F 

First 256 bytes of program memory:

0: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF 
...
F0: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF 


Make sure you have the serial monitor baud rate set to 115200 (bottom RH corner).

Your figures may vary a bit but you should certainly see the lines in bold which indicate it detected the chip type.

If you see this, you can skip down to the section "Programming the Bootloader".

If not, read on ...

Chip not detected


If, instead of the above, you see this:

Board Detector Output


Atmega chip detector.


This means that the target board has not entered programming mode.

First, double-check your wiring.

If you are certain that is correct, then your target chip is probably configured to need a crystal. The crystal generates the processor clock, and without it you cannot program it.

If you bought a "raw" chip direct from the manufacturer you should not have this problem, as the chips default to using an internal 8 MHz oscillator. But if you got your chip from a third party who already installed a bootloader, then the "fuse settings" may have been changed to expect the crystal.

So, we'll have to install one, or we can't program it.

The exact frequency of crystal isn't critical, probably something between 4 MHz and 20 MHz would do, enough to get the processor to start up.

Install the legs of the crystal so they connect to pins 9 and 10 as shown:



Also connect a 22 pF or thereabouts (eg. 18 pF or 20 pF) capacitor between each leg and ground, as shown.

Another angle:



In my case I used an 8 MHz crystal.

An alternative is to use a "resonator" which is similar in behaviour to a crystal, and does not require capacitors:



Connect the outside legs of the resonator to pins 9 and 10, and the middle leg to ground.

With the crystal in place I can now check this chip:

Board Detector Output


Atmega chip detector.
Entered programming mode OK.
Signature = 1E 95 0F 
Processor = ATmega328P
Flash memory size = 32768
LFuse = FF 
HFuse = DA 
EFuse = FD 
Lock byte = FF 
Bootloader in use: Yes
EEPROM preserved through erase: No
Watchdog timer always on: No
Bootloader is 2048 bytes starting at 7800

Bootloader:

7800: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF 
7810: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF 
...
7FE0: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF 
7FF0: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF 

MD5 sum of bootloader = E0 DE EB D3 C3 F5 60 21 2A F1 7C 68 B9 34 4B AE 

First 256 bytes of program memory:

0: 0C 94 34 00 0C 94 51 00 0C 94 51 00 0C 94 51 00 
10: 0C 94 51 00 0C 94 51 00 0C 94 51 00 0C 94 51 00 
...
E0: B0 91 07 01 30 91 08 01 01 96 A1 1D B1 1D 23 2F 
F0: 2D 5F 2D 37 20 F0 2D 57 01 96 A1 1D B1 1D 20 93 


This particular chip does not seem to have a bootloader (it is all 0xFF).

Alternate clock source


As an alternative to a crystal or resonator, the revised version of the sketch outputs a 8 MHz clock on pin D9 of the programming board. Thus you just need to connect D9 on the programming board to pin 9 of the target board and this will provide a clock signal, enough for you to upload the bootloader and change the fuses.



Extra wire shown in yellow.

Programming the Bootloader


Now that we see some action through the chip detector sketch, it is time to load up the bootloader programming sketch:

http://gammon.com.au/Arduino/Atmega_Board_Programmer.zip

Upload the sketch to your "programming" Uno (or other board) and enter the serial monitor (at 115200 baud). You should see this:

Chip Programmer Output


Atmega chip programmer.
Written by Nick Gammon.
Entered programming mode OK.
Signature = 0x1E 0x95 0x0F 
Processor = ATmega328P
Flash memory size = 32768 bytes.
LFuse = 0xFF 
HFuse = 0xDA 
EFuse = 0xFD 
Lock byte = 0xFF 
Bootloader address = 0x7E00
Bootloader length = 512 bytes.

MD5 sum of current bootloader = DE 03 FE 65 A6 76 5C AA 8C 91 34 3A CC 62 CF FC 

Type 'L' to use Lilypad (8 MHz) loader, or 'U' for Uno (16 MHz) loader ...


Now you can choose from using a bootloader designed to run at 8 MHz without a crystal (the Lilypad loader) or one designed to run at 16 MHz with a crystal or resonator (The Uno loader).

The choice is yours, it depends if you are planning to use a crystal or not. The crystal (or resonator) lets you run at the higher speed of 16 MHz.

Since I am going for a minimal application, I'll type "L" and hit the Send button:


Using Lilypad 8 MHz loader.
Type 'V' to verify, or 'G' to program the chip with the bootloader ...


Type "G" to program (Go) and you should see this:


Erasing chip ...
Writing bootloader ...
Committing page starting at 0x7E00
Committing page starting at 0x7800
Committing page starting at 0x7880
Committing page starting at 0x7900
Committing page starting at 0x7980
Committing page starting at 0x7A00
Committing page starting at 0x7A80
Committing page starting at 0x7B00
Committing page starting at 0x7B80
Committing page starting at 0x7C00
Committing page starting at 0x7C80
Committing page starting at 0x7D00
Committing page starting at 0x7D80
Committing page starting at 0x7E00
Committing page starting at 0x7E80
Committing page starting at 0x7F00
Committing page starting at 0x7F80
Written.

MD5 sum of new bootloader = 7D 35 D3 57 99 DD 95 EC FA 90 34 90 34 1F F1 30 

Verifying ...
No errors found.
Writing fuses ...
LFuse = 0xE2 
HFuse = 0xDA 
EFuse = 0xFD 
Lock byte = 0xEF 
Done.
Type 'C' when ready to continue with another chip ...


This takes about one second.

Now the chip has a bootloader, and you can disconnect the power (USB cable) and remove the crystal or resonator.

The bootloader installation process changed the fuses on the processor, so it now runs from the 8 MHz internal oscillator. You can confirm by removing the crystal and two capacitors, reconnecting the power, and verifying:

Chip Programmer Output


Atmega chip programmer.
Written by Nick Gammon.
Entered programming mode OK.
Signature = 0x1E 0x95 0x0F 
Processor = ATmega328P
Flash memory size = 32768 bytes.
LFuse = 0xE2 
HFuse = 0xDA 
EFuse = 0xFD 
Lock byte = 0xEF 
Bootloader address = 0x7E00
Bootloader length = 512 bytes.

MD5 sum of current bootloader = 7D 35 D3 57 99 DD 95 EC FA 90 34 90 34 1F F1 30 

Type 'L' to use Lilypad (8 MHz) loader, or 'U' for Uno (16 MHz) loader ...


Type "L" ...


Using Lilypad 8 MHz loader.
Type 'V' to verify, or 'G' to program the chip with the bootloader ...


Type "V" to verify ...


Verifying ...
No errors found.
Done.
Type 'C' when ready to continue with another chip ...


This confirms that the chip now works "stand alone" and that the bootloader is installed correctly.

Programming a sketch


To program from a modern Windows/Mac/Linux PC with USB ports, we need to somehow convert a USB port into serial data. This is where the FTDI cable comes in handy. I'll use like this:



You can get these from, for example:


  • https://www.adafruit.com/products/70
  • http://www.sparkfun.com/products/9718
  • eBay


... for around $US 18 to $20.

We can disconnect our breadboard from the Uno we used to program the bootloader, and using hook-up wire, connect it to the FTDI cable like this:



Close-up of the way the wire goes into the FTDI cable:



Note the orientation. The black wire is pin 1 (Gnd) and pin 2 (CTS) is not used.

So, five wires in total:

Wiring


FTDI cable      Target board

Pin 1 (GND)     Gnd (blue)
Pin 2 (CTS)     not connected
Pin 3 (Vcc)     +5V (red)
Pin 4 (TxD      Pin 2 (RxD) (white)
Pin 5 (RxD)     Pin 3 (TxD) (orange)
Pin 6 (RTS)     To Reset via 0.1 uF capacitor (green)


The capacitor is there to turn the RTS signal into a pulse, so that when the computer brings RTS low, it briefly pulls reset low, and then the pull-up resistor charges the capacitor again, bringing reset high again.



Oscilloscope output showing reset line being pulled low briefly.

Note that TxD on the FTDI cable goes to RxD on the chip, and vice-versa. This is because with serial comms one side transmits and the other side receives.

Example sketch


Since we don't have any LEDs (yet, muahahaha) let's just try some simple serial comms.

Go to the File menu -> Examples -> Communication -> ASCIItable and load that sketch up.

Change the baud rate to 115200 in the sketch:


void setup() 
{ 
  Serial.begin(115200);    // <----- here

  // prints title with ending line break 
  Serial.println("ASCII Table ~ Character Map"); 
} 


Since we uploaded the Lilypad bootloader, go the Tools menu -> Board and choose "Lilypad Arduino w/ Atmega328".

Now upload the sketch (Ctrl+U or Command+U on the Mac).

Open the serial monitor and you should see:


ASCII Table ~ Character Map
!, dec: 33, hex: 21, oct: 41, bin: 100001
", dec: 34, hex: 22, oct: 42, bin: 100010
#, dec: 35, hex: 23, oct: 43, bin: 100011
...
v, dec: 118, hex: 76, oct: 166, bin: 1110110
w, dec: 119, hex: 77, oct: 167, bin: 1110111
x, dec: 120, hex: 78, oct: 170, bin: 1111000
y, dec: 121, hex: 79, oct: 171, bin: 1111001
z, dec: 122, hex: 7A, oct: 172, bin: 1111010
{, dec: 123, hex: 7B, oct: 173, bin: 1111011
|, dec: 124, hex: 7C, oct: 174, bin: 1111100
}, dec: 125, hex: 7D, oct: 175, bin: 1111101
~, dec: 126, hex: 7E, oct: 176, bin: 1111110


Job done! You now have a "bare bones" Arduino-compatible processor on a breadboard! Enjoy!

Example using battery power


This photo shows the breadboard processor driving another breadboard with 4 x 74HC595 shift registers driving 32 LEDs, as described here:

http://www.gammon.com.au/forum/?id=11518



The whole thing is powered by 3 x 1.5 AA batteries.


Board detector sketch


The sketch to detect the chip type is described here:

http://www.gammon.com.au/forum/?id=11633

- Nick Gammon

www.gammon.com.au, www.mushclient.com
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Posted by Nick Gammon   Australia  (19,385 posts)  [Biography] bio   Forum Administrator
Date Reply #1 on Mon 14 May 2012 04:44 AM (UTC)  quote  ]

Amended on Mon 14 May 2012 07:34 AM (UTC) by Nick Gammon

Message
Atmega1284P minimal board


Following on from the above post, I adapted the same procedure to wire up a Atmega1284. This has somewhat more RAM (16 Kb) and somewhat more program memory (128 Kb).



Minimal wiring


The chip pinouts are:



The very basics are to wire +5V to VCC and AVCC (AVCC is the analog power in), plus both GND pins (normal and analog).



Connected are:



  • +5V to VCC (pin 10) (red wire)
  • GND to pin 11 (bare wire)
  • +5V to AVCC (pin 30) (red wire)
  • GND to pin 31 (blue wire)
  • Connect /RESET (pin 9) to +5V via a 10K pull-up resistor
  • 16 MHz Crystal between pins 12 and 13
  • 18 pF Capacitor between pin 12 and Gnd (for the Crystal)
  • 18 pF Capacitor between pin 13 and Gnd (for the Crystal)



We also add a 0.1 uF decoupling capacitor to both sides of the board.

There is also a 10K pull-up resistor for the reset pin. Although the chip has a built-in pull-up, this appears to make it reset more reliably when downloading new programs.

There are wire links connecting the Gnd and +5V of both sides of the breadboard together. The links are not visible in all the photos because I forgot them initially ... oops. The digital side worked without them.

You could run without the crystal, but the Optiboot loader which we install in a minute sets the fuses to expect one.

Install the bootloader


I'm going to use my "Board Programmer" sketch to install the Optiboot loader. To do this we need to connect up a Uno (or similar) to the SPI pins as follows:





Programming Uno     Target board

D10 (SS)            Reset - pin 9 (green)
D11 (MOSI)          Pin 6 (yellow)
D12 (MISO)          Pin 7 (orange)
D13 (SCK)           Pin 8 (black)

Gnd                 Gnd (blue)
+5V                 +5V (red)


Now we'll install the bootloader upload sketch onto the Uno and run it (set the serial monitor to 115200 baud).

http://gammon.com.au/Arduino/Atmega_Board_Programmer.zip


Atmega chip programmer.
Written by Nick Gammon.
Entered programming mode OK.
Signature = 0x1E 0x97 0x05 
Processor = ATmega1284P
Flash memory size = 262144 bytes.
LFuse = 0xFF 
HFuse = 0xDE 
EFuse = 0xFD 
Lock byte = 0xEF 
Bootloader address = 0x1FC00
Bootloader length = 1024 bytes.

MD5 sum of current bootloader = 77 2F 81 F1 7F 1E 46 93 97 B4 54 23 4C 44 72 68 

Type 'V' to verify, or 'G' to program the chip with the bootloader ...


Erasing chip ...
Writing bootloader ...
Committing page starting at 0xFE00
Committing page starting at 0xFE80
Committing page starting at 0xFF00
Committing page starting at 0xFF80
Written.

MD5 sum of new bootloader = 77 2F 81 F1 7F 1E 46 93 97 B4 54 23 4C 44 72 68 

Verifying ...
No errors found.
Writing fuses ...
LFuse = 0xFF 
HFuse = 0xDE 
EFuse = 0xFD 
Lock byte = 0xEF 
Done.
Type 'C' when ready to continue with another chip ...


There is another sketch you can install onto the programming Uno which detects your fuse settings:

http://gammon.com.au/Arduino/Atmega_Fuse_Calculator.zip



Atmega fuse calculator.
Written by Nick Gammon.
Entered programming mode OK.
Signature = 0x1E 0x97 0x05 
Processor = ATmega1284P
Flash memory size = 262144
LFuse = 0xFF 
HFuse = 0xDE 
EFuse = 0xFD 
Lock byte = 0xEF 
OCD Enable.............................. [ ]
JTAG Enable............................. [ ]
Enable Serial (ICSP) Programming........ [X]
Watchdog Timer Always On................ [ ]
Preserve EEPROM through chip erase...... [ ]
Boot into bootloader.................... [X]
Divide clock by 8....................... [ ]
Clock output............................ [ ]
Bootloader size: 1024 bytes.
Start-up time: SUT0: [X]  SUT1: [X] (see datasheet)
Clock source: low-power crystal.
Brownout detection at: 2.7V.


With the bootloader installed we can now program using an FTDI cable.

Programming a sketch


See earlier post about where to get the FTDI cable from.




FTDI cable      Target board

Pin 1 (GND)     Gnd (blue)
Pin 2 (CTS)     not connected
Pin 3 (Vcc)     +5V (red)
Pin 4 (TxD      Pin 14 (RxD0) (white)
Pin 5 (RxD)     Pin 15 (TxD0) (orange)
Pin 6 (RTS)     To Reset via 0.1 uF capacitor (green)


Now you need to grab the configuration files which tell the IDE how to program the Mega1284P. Once source is here:

https://github.com/maniacbug/mighty-1284p

As instructed on his page, unzip the download and place the entire resulting folder inside the "hardware" folder in your sketches folder, like this:



(I had some other folders for different processors).

Here is another view of how it should look:



This it the "hardware" folder which should be at the same level as "libraries" and the same level as your own sketches, in the Arduino sketches folder. You may need to create the "hardware" folder if it doesn't exist already.

Then close and re-open the IDE for it to recognize the new board.

Now you shoule be able to select "Mighty 1284P 16 MHz using Optiboot" from the Board menu:



This is why I installed the 16 MHz crystal, because this bootloader expects to run at that speed.

Now you should be able to upload a test sketch, and have it work. :)

Latest version of sketches


The latest versions of the sketches mentioned above can be downloaded from GitHub:

https://github.com/nickgammon/arduino_sketches

- Nick Gammon

www.gammon.com.au, www.mushclient.com
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