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Topic: Arduino compatible board assembly. (Read 1 time) previous topic - next topic

Yarash

I have seen around many diagrams for an
Arduino compatible board, there are some details
That vary from one diagram to the other,

In the attached diagram the capacitors are all 0.1uf
And in many others they are 1uf

1. What should they be?

2. in the attached, i think i understand it correctly
But what should the capacitors connected to the
16Mhz crystal be?

3.both on the ICSP and the FTDI
there is a +5V, should this come from the supply
Feeding the arduino, or is this coming externally
By just connecting the FTDI/ICSP plug (from computer)

4.I remember reading that you can save the space used
For the bootloader by using the FTDI to upload the program.
If so, would the Arduino software still be able to upload the sketch?


Thanks.

CrossRoads

Power supply decoupling caps are 0.1uF.
Caps on the 16MHz crystal are 22pF.
+5V can be from USB or from external supply. Do not connect them together. Connect the grounds together.
FTDI supports serial programming when a bootloader is on the chip.

It can be used as an AVR ISP: http://www.geocities.jp/arduino_diecimila/bootloader/index_en.html
but that method is not for the feint of heart 8)

It is much more straightforward to use a chip/board designed to be  used as a programmer:
http://www.mdfly.com/index.php?main_page=product_info&cPath=5&products_id=415
http://www.hobbyking.com/hobbyking/store/__21321__USBasp_AVR_Programming_Device_for_ATMEL_proccessors.html

or use an Arduino as an AVR ISP:
http://www.gammon.com.au/forum/?id=11638
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.


MarkT

The exact value of decoupling capacitors is not very crucial, but they should be ceramic and
they need to be right next to the relevant pins of the chip to work properly.

Having both 0.1uF and 10uF decoupling caps for each supply is commonly done to improve
the effectiveness (matters more for analog input quality), the 10uF can be electrolytic.

A ground-plane is a very good idea - failing that ensure there's a whole network of ground traces
around all the board.

The caps on the crystal ideally should match the crystal's specifications, but in practice that
means 18 or 22pF  (the load capacitance the crystal sees is half the value of these capacitors
in parallel with the input capacitance of the chip's oscillator and any stray capacitance - sounds
complex, just use 22pF!
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Yarash


Power supply decoupling caps are 0.1uF.
Caps on the 16MHz crystal are 22pF.
+5V can be from USB or from external supply. Do not connect them together. Connect the grounds together.
FTDI supports serial programming when a bootloader is on the chip.

It can be used as an AVR ISP: http://www.geocities.jp/arduino_diecimila/bootloader/index_en.html
but that method is not for the feint of heart 8)

It is much more straightforward to use a chip/board designed to be  used as a programmer:
http://www.mdfly.com/index.php?main_page=product_info&cPath=5&products_id=415
http://www.hobbyking.com/hobbyking/store/__21321__USBasp_AVR_Programming_Device_for_ATMEL_proccessors.html

or use an Arduino as an AVR ISP:
http://www.gammon.com.au/forum/?id=11638


So, can i use an ISP for programming either the boot
Loader or a sketch?

And if so, i guess the FTDI would be needed only
If i want to program a sketch using the arduino boot loader
And i have no USB module in the circuit?

Thanks!

CrossRoads

Yes - use ISP for bootloader, or sketch with no bootloader.

Use USB/Serial adapter to down via the bootloader.
Use offboard USB/Serial adapter if there is not one on the board.

An example - FTDI module & AVR ISP connector bootloading a '1284P card.
AVR ISP in this case is Atmel AVR ISP MKii, only senses power, FTDI module is actually powering the card.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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