Show Posts
Pages: 1 ... 441 442 [443] 444 445 ... 582
6631  Development / Suggestions for the Arduino Project / Re: New arduino language on: May 01, 2011, 05:04:17 am
The 1284 has to be the best overall chip in the AVR lineup I think, 2x the 2560 RAM, one extra UART which is all most need, gobs of flash and IO.

I'm using it on two boards about to go to PCB fab.

______
Rob
 
6632  Using Arduino / Networking, Protocols, and Devices / Re: Sparkfun as supplier on: May 01, 2011, 04:55:52 am
I've used them 2 or 3 times and been well happy.

______
Rob
6633  Using Arduino / Programming Questions / Re: Arduino & thread on: May 01, 2011, 04:49:06 am
That was on the Old MacDonald variant of that processor wasn't it?

______
Rob
6634  Using Arduino / Sensors / Re: LDR and his scope on: May 01, 2011, 03:06:21 am
You can reduce the reference voltage, see analogReference(), select an external reference and apply a much smaller voltage to the AREF pin.

You can also select the internal 1v1 reference which may be closer to your needs.

______
Rob
6635  Using Arduino / Programming Questions / Re: Arduino & thread on: May 01, 2011, 02:39:30 am
And then there was XPR (eXecute PRogrammer) LDN (LoaD Nothing) and a lot of other funny ones around a few years ago.

______
Rob
6636  Using Arduino / Programming Questions / Re: Arduino & thread on: May 01, 2011, 12:17:35 am
We used QNX for building control on a 6809-based computer in the 80s, I don't remember the details but it's probably fair to say it had 64k RAM.

One assumes though that QNX has gone the bloatware track like everything else.
______
Rob
6637  Using Arduino / Programming Questions / Re: Serial - Preventing significant code/loop slowdown on: April 30, 2011, 10:13:11 pm
I seem to remember on a recent post that there was a bug that screwed with the 300 speed.

______
Rob
6638  Using Arduino / Networking, Protocols, and Devices / Re: SPI multi master on: April 30, 2011, 04:41:35 am
In any multi-master test-then-do arrangement race conditions are a potential issue.

CrossRoads scheme gets around this I think but will cost you some time.

You still haven't said if you can afford to miss a reading or two and if readings from every chip have to be aligned, for example if this is a logic analyser front end you can't miss a single reading, however if you're looking at batteries discharging (OK unlikely given the speeds you've mentioned smiley) it doesn't matter.

Knowing the application might help as well.

______
Rob
6639  Using Arduino / Networking, Protocols, and Devices / Re: Using data from Arduino to toggle pic on: April 30, 2011, 04:24:33 am
Quote
I didn't read your post several times, because I thought it was about communicating with a microprocessor called a "pic"
I haven't read read this before for the same reason, I only read it now because there was bugger all new on the forum smiley

______
Rob
6640  Using Arduino / Programming Questions / Re: New regular expression library released on: April 30, 2011, 01:31:14 am
Good one Nick, I think that will become very useful.

______
Rob
6641  Using Arduino / Programming Questions / Re: Using a pointer to increment on: April 29, 2011, 11:01:47 pm
Quote
does the pointer increment the amount of bytes for that variable type?
Yes.

I'm not sure about ptrlong+=1 but ptrlong++ will add the size of the data type being pointed to.

______
Rob
6642  Using Arduino / Networking, Protocols, and Devices / Re: A "Minimal" Arduino/XBee/Pachube Sensor Network on: April 29, 2011, 09:23:21 pm
The link to the sketches on your blog doesn't seem to work.

I actually am interested in the more complicated version with different sensor types, having just designed the PCBs for about 10 different types myself (wired though, not wireless).
_____
Rob
 
6643  Using Arduino / Programming Questions / Re: Problem with NewSoftSerial on PORTB on: April 29, 2011, 11:52:06 am
Can you post all the code, often problems are elsewhere, for example

digitalWrite(UD,DOWN);

makes no sense in the above context because "DOWN" is not a standard symbol, maybe it's been defined somewhere else and maybe that definition was incorrect.

_____
Rob
  
6644  Using Arduino / Networking, Protocols, and Devices / Re: SPI multi master on: April 29, 2011, 08:00:42 am
If it's that tight you'll have to get creative.

Any form of multi-master needs arbitration and without extra hardware that will take time and get complicated.

The SPI hardware is really just a fancy shift register.

To use SS or any pin as an interrupt or input to tell the slaves (sorry I have to think multiple slaves and one master) to load the data will I think be too slow.

I'm thinking the other way around, the slaves load the data into the SPI register unless told not to.

Use a pin as a load enable (we'll call it EN), ie during the brief inter-ADC reading period the slaves load 8 bits of data into the SPDR reg unless EN is high, in which case the reading may be discarded or not depending on if you really need every one.

So on the slave chips the code is like this

Code:
read ADC
if EN == LOW
   write value to SPDR

All slaves are daisy chained so the master does the following

Code:
raise EN
for (n = 0; n < number_of_slaves; n++)
    SPI.transfer
lower EN

This of course means that for ( slaves * 8 ) bit times the slaves are effectively disabled from updating their ADC reading. This may or may not matter depending on the number of slaves and the importance of getting every reading.

You can maybe speed this up by reading say 8 slaves in parallel. Run all the slave MISO pins to digital inputs of the master. So assuming <= 8 slaves

Code:
   raise EN
   pulse clock pin
   bits0 = PORTD;
   pulse clock pin
   bits1 = PORTD;
   pulse clock pin
   bits2 = PORTD;
   pulse clock pin
   bits3 = PORTD;
   pulse clock pin
   bits4 = PORTD;
   pulse clock pin
   bits5 = PORTD;
   pulse clock pin
   bits6 = PORTD;
   pulse clock pin
   bits7 = PORTD;
   lower EN

It looks bad but might be faster than getting 64 bits bytes via the SPI. Of course the bytes have to be reconstructed but that can be done later.

If you need all 10 ADC bits then I guess the above has to be duplicated (but only two more pulses needed) and the slaves are once again disabled for the duration of the transfer.

If you absolutely can't afford to lose a reading and need 10 bits I think you'll have to throw hardware at the problem.

_____
Rob
6645  Using Arduino / Programming Questions / Re: Code don't do what it should do on: April 29, 2011, 04:35:35 am
Yep, good point, written in haste.

______
Rob
Pages: 1 ... 441 442 [443] 444 445 ... 582