Arduino Mega 2560 mega on Flexible PCB

Projects General Guidance
1

Hi,
I am trying to make a Arduino Mega 2560 on a flexible PCB for a hobby project I am working on(Haven't started on it yet though! ). I was wondering if anyone here had done something similar for Mega(I have seen the Seeduino project Seeeduino Film, maybe the first Arduino(TM) compatible board on FPC - Latest Open Tech From Seeed). I would like to know if there is something I should keep in mind before attempting something like this(Soldering Atmega2560 TQFP100 package on flex PCB? ) or something which could prevent me from making the flexible version of the board work.
Couple of more doubts...

  1. Should I use Atmega 16U2 in place of a FT2232 chip? because I cant find any advantage of using a uC for this? Atmega 16U2 is I think more expensive than the other one?? Will the board work the same way if I use FT2232?

  2. What all should I leave on the board to create a barebones board of Mega2560? When I saw the schematic, I am guessing the uC would work on its own if I just have the power supply regulator + decoupling caps + Atmega2560 IC and crystals of 16MHz. Is there anything I should keep on the board?(Assuming the chip is programmed and I don't need to program it again)

  3. If I do the connections as mentioned in Step 2 will I be able to program it in someway?(I am assuming ISP or JTAG would work if I take out the pins)

Hoping someone can respond :slight_smile:

2

#2 with ftdi or icsp headers sounds good.

3

22 pf caps for xtal.

4

Thanks Crossroads :slight_smile:
I am thinking of dropping the Ft2232 chip. Will program via ICSP.

In the barebones board I am thinking of including(all SMD ones) Atmega2560 IC + power supply regulator + decoupling capacitors + 16MHz crystal + crystal capacitors + take out the ICSP pins.

One general question though, why did official arduino choose Atmega16u2 as a replacement IC for ft2232 ics? I am not seeing an advantage... Am I missing something?

5

16u2 is reprogrammable for HID use or whatever. Ft232 is not.
Might be less expensive also.

6

Assuming the chip is programmed and I don't need to program it again

Will program via ICSP.

I am thinking of dropping the Ft2232 chip. take out the ICSP pins

How do you plan to program the chip?

Rob

7

If you have ICSP you don't need serial. Basically no arduino boot loader. However I would breakout the JTAG pins so that you can do some debugging if need be.

8

jtag needs special tools and software. see atmel.com
not many people have them.

9

Graynomad:

Assuming the chip is programmed and I don't need to program it again

Will program via ICSP.

I am thinking of dropping the Ft2232 chip. take out the ICSP pins

How do you plan to program the chip?

Rob

I have an uno board so I am thinking I can program the Atmega2560 board via ISP.
Or I was also thinking on the lines of having a TQFP package holder and program it with a Mega board and drop and solder it in the final flexible PCB version...

mrjonny2:
However I would breakout the JTAG pins so that you can do some debugging if need be.

Yup. Thinking about it. I have a JTAG ICE3 so it should help in debugging...

10

OK, is doesn't matter what device you program it with (Uno/Mega/JTAG) you still need access to the ISP pins, but it you plan to do this before soldering that's ok, just hope like hell you never have to change the code :slight_smile:

Rob