Hi guys,

Thanks for the responses.

I should have mentioned that I can get 500,000 on a standard Arduino Mega 1280 reliably... Has anyone else got experience with fast communication with the new more powerful due?

 

Has anybody tested the what USB serial baud rates/speeds are achievable using a standard virtual COM port on a computer? How fast can this board go in practice??

I am hoping there will be improvements on the standard Arduino due to the faster processor...

Are there any other options for faster communication by using alternatives to a virtual COM port? What is the best data rate achievable (using any approach?)

Thanks

Hi again,

I have copied and pasted the code from

http://arduino.googlecode.com/svn/trunk/hardware/arduino/cores/arduino/wiring_digital.c

and then recompiled my code by pressing the verify (triangle) button, and then re-uploaded.

Is this all that is necessary to implement the changes, and therefore hopefully the fix?

If so, there may be other causes for glitches when controlling servos using the servo library. It seems to glitch less, but still glitches, especially during the time following an update to the servos - would reducing the serial baud rate effect/help?

Great, thanks alot for the helpful replies:

I will try bperrybap's suggestion first, but it would be nice to have nickvd's compiled version too.

@ nickvd: Could you please put it online somewhere, or maybe email it too me? sensev at hotmail com

Thanks again for the responses  

PS I am using an arduino mega with version 0018.

I have come across a bug, but luckily it looks documented and solved:

http://code.google.com/p/arduino/issues/detail?id=146

the author comments recently:

"I made the changes Paul suggested. If you've been having problems with this, can you try the latest SVN revision and see if it helps?"

Does this mean I have to compile the latest SVN revision as per

http://code.google.com/p/arduino/wiki/BuildingArduino

Or are there any compiled/built windows ones out there; the last arduino build seems to be around feb, but the bug seems to have been fixed around june.

Or can I just copy and paste some code, or update some specific files.

Any help greatly appreciated  

I have successfully used Pduino for Max (thanks a lot to those involved!)
Is there anything that successfully communicates in both both directions (read & write) for the Mega?
I am relatively new to Arduino - I would ideally be after something that works "out of the box", but if more is required then so be it.

Thanks

So what is it that you are trying to do?

Yes!

The mega has tons of I/O pins available so it's unlikely that you want to use pins 0 &1 because your short of pins?

You would be surprised, 60 servo's. Is there a clever way to reduce pin count? I know there is a possibility with the TLC5940, but I will need to get my head round that chip/code, even though Alex Leone (the TLC5940 library creator) has been very helpful.

Thanks for the quick response  

I am using Serial communication using a usb cable the standard way using "Serial.begin(9600)" but although I set pins 0 and 1 to output, i cannot control them.

I understand that "Pins 0 and 1 are also connected to the corresponding pins of the FTDI USB-to-TTL Serial chip." - does mean that I cannot use them when I am using Serial or something?

I have set the output mode using "pinMode(0, OUTPUT);" which works on all other pins except 0 and 1.

Is there a way I can use Serial -  and pins 0&1 for digital out?

Cheers

I have a setup involving a few Arduino mega boards. I can communicate with all of them using a usb hub (successfully), but I was worried about the load on my laptop.

Does anyone have any idea about about how resource intensive serial communication is on a laptop (dual core windows 7) at about 100kbps?

I was thinking that instead of having multiple serial connections to each of the Arduino mega boards, I would have less connections (but the same amount of data), and use I2C between the Arduinos.

Does this make any sense?

Your thoughts appreciated

Chendy

Great, I will have a experiment.

I was testing on cheap one out with one Arduino, but it wasn't self powered - I am aware of the 500ma issue, however I thought a single Arduino should be fine. I external power my Arduino anyway.

Cheers for the responses, I will post the outcomes of my experiments with some hubs.  

I understand that USB hubs can work, however the one I have doesn't work; there is no serial port detected in the Arduino IDE.
 
Is there anything I can do to make USB hubs work with 3 Arduinos, each using serial?

Can anybody recommend me a special brand & model that works with serial @ 100000 baud on each Arduino?

Thanks in advance

Thanks for the replies.
I thought I would say I have received a couple of sample "MAX485 CPA" chips from the nice people at Maxim  

Thanks Daniel for the swift replies. Greatly Appreciated.

I have requested a couple of MAX485CPA+.
The process was very smooth however I have to waiting a day to see if i have actually been approved by the Maxxim lot.

I should have made the following clear in my first posts:
- I am a newbee and i have little/no experience in electronics
- My plan of action was to follow the dmx512 resources on the playground section of arduino.cc

Anyway thanks again and I'll hopefully be having some MAXMSP controlled DMX laser action soon!

Thanks for the response.

I have registered for access to samples, but which max485 chip to request?

MAX4850ETE+  ? or
MAX4851ETE  ? or
MAX4851HETE  ? or
MAX4854ETE  
MAX4853ETE  or etc.

There are so many when isearch for "max485"

which is the best or most suitable?

Hi.
I want to bu a Max485 chip for DMX with arduino. Is this the same as the RS485?
I cant find on google where to buy this chip.
Ideally i would like to by one from uk but europe is fine.

What do you type to google to find these?

Any help greatly appreciated