How to make a custom Arduino board

Other Hardware Hardware Development
1

Hi all
I have a really simple question. I'm developing a small robotics project and i wanted it to be Arduino controlled. I looked at the Arduino Uno board and i found that there are some parts that i don't need. I'd remove the voltage regulator (because i have the power regulated somewhere else), so i have to look at Atmega328 voltage specs, and the part with the Atmega16u2. As i understood, it's only a USB to UART bridge, so i can substitute it with a FT232 or similar or use a MAX232 and connect to a serial port, right? If i do this, will i be able to program the Atmel from Arduino IDE (as long as i upload the bootloader on it with an atmel programmer)? Will it work with no handshake (i mean only with RX and TX) or i need to wire also other signals (RTS and CTS)?

Moreover, does the core part require other things rather than the microcontroller, the crystal at 12MHz, the bypass capacitors and the resistor on RESET? I mean, with Atmega328, 12MHz resonator, one 100nF capacitor and a pullup resistor i can have a working arduino uno?

And.. is there an italian forum too or the only supported language is english? :stuck_out_tongue:

Thank you

2

lots of questions

and the part with the Atmega16u2. As i understood, it's only a USB to UART bridge

correct

so i can substitute it with a FT232 or similar or use a MAX232 and connect to a serial port, right?

correct

will i be able to program the Atmel from Arduino IDE (as long as i upload the bootloader on it with an atmel programmer)?

yes, the old arduinos were serial only, and as far as both ends are concerned its serial, so its all good

Will it work with no handshake (i mean only with RX and TX) or i need to wire also other signals (RTS and CTS)?

it will if you manually reset the board when you want to program it (wait till it says uploading and hit the reset button) otherwise you will need a control line, I dont remember which one reset is on off hand

Moreover, does the core part require other things rather than the microcontroller, the crystal at 12MHz, the bypass capacitors and the resistor on RESET? I mean, with Atmega328, 12MHz resonator, one 100nF capacitor and a pullup resistor i can have a working arduino uno?

sort of, the 328P runs on a16Mhz crystal, and you will need a couple caps for that, or you can get a ceramic resonator which is a handy 3 pin package (2 xtal 1 ground in the middle).

you might want a reset button, you will need it if your going to manually reset it for programming. but otherwise yea the main functionality of arduino is all on the 328P

also the pins are not mapped directly, so here is a handy chart
http://arduino.cc/it/Hacking/PinMapping168

And.. is there an italian forum too or the only supported language is english?

yes, there are a few language sections in the forum

http://arduino.cc/forum/index.php/board,34.0.html

3

Thank you so much for your reply

Osgeld:
it will if you manually reset the board when you want to program it (wait till it says uploading and hit the reset button) otherwise you will need a control line, I dont remember which one reset is on off hand

After having read this i downloaded eagle and followed every path related to the reset. And then.. i found that it was already explained online :wink: at arduino.cc/en/Main/ArduinoBoardUno, paragraph Automatic (Software) Reset. So it's the DTR line, connected through a capacitor to the reset line.
Thank you so much for your help. Now i'm (almost) ready to start this project :slight_smile:

4

You know, if you don't need the boot loader you can simply program the AVR processor using the 6 pin ICSP header. Unless you need to field upgrade the device, you don't need the boot loader.

5

You can build up a minimal design board also with a handful of parts from www.dipmicro.com
http://store.nkcelectronics.com/arduino-runtime-board-rev-b.html

Or for something more arduino shaped, build up a Serial arduino from this bare board.
http://www.mouser.com/ProductDetail/Arduino/A000006/?qs=sGAEpiMZZMs0PWRNvpRp0ARF1Zt0Kmpi.

In both cases, you can wire up and FTDI Basic breakout cable to connect to the header pins for serial downloading after the bootloader is installed.