Xbee wrong characters recieved

[ciseco]

Xbee wrong characters recieved - please help

Hi all,

I've a wierd one, I've got a pile of various xbee's and PICAXE's and my program works perfectly at 2400bps on everything I've built. When sped up to 4800bps (yes both code and xbee) it works perfectly only on 18x's on REVED's AXE210 board.

At 4800bps on a 28x1 or a 40x1 the received characters are shifted, a space (dec 32) comes out as @ (dec 64) and "a" (dec 97) comes out as a symbol (dec 193) so everything is screwy.

Characters sent from the PICAXE to the xbee come through perfectly (PC running hyperterm to test), it's just recieving into the PICAXE which isn't right.

I've built 2 different versions and tried straight off their AXE210 board to the 28/40 always the same thing. I have precision voltage regs running at 3.306 and dead on 5v as the supplied zetex one's were rubbish.

I suspected timing and tech support thought so too and suggested using setfreq em4 or e4 to test, does exactly the same thing.

Anyone think I need to pull up or down the serial input? or the rest of the inputs? or put in a cap? or that the tollerances of the 28/40 dont like 3.3v logic when running that fast?

I'm running short of ideas?

Miles
________
buy vapir vaporizer

 

[papaof2]

The problem with the 28x1 and serial speed has been reported before. The usual resolution is to use calibfreq to tweak the speed slightly.

I found this:
"you need to play with the calibfreq command. Try these figures first -1, -2, 1, 2, then try bigger numbers.

The last batch of 28X1 chips I got had to be set to calibfreq -4 for them to work with my overclocked 08M. But I have found the 18X range to be pretty good.

My experience is that serout and serin are pretty sensitive to the calibfreq command."

in this thread:
http://www.picaxeforum.co.uk/showthread.php?t=8883

John

 

[ciseco]

John, I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU,I LOVE YOU

can you tell I'm pleased, calibfreq -5 sorted it

Miles
________
Nash Ambassador history

 

[Dippy]

Marriages available at extra charge.

 

[ciseco]

bloomin thing, I'm now having to -5 to receive at 4800 then set back to 0 to send at 2400 to lcd then back to -5 for 4800, at least it's working

is this something the tech guys could tweak?

sorry dippy already engaged, john will just have to have my love on the quiet

John, I've just worked out I've spent a number of working days (maybe a week) and a good few phone calls trying to get this sorted, previously I offered anyone a drink on me, I always stay true to my word, if you have a paypal account I'd be delighted to send over a few dollars, just name your poision????

Miles
________
Technological Institute

 

[papaof2]

My preferred mood changing "drug" is chocolate (preferably dark, at 75% cacao or higher).

John

 

[ciseco]

Well if youv'e got a paypal account, go find the biggest damn bar in the super market you can find and I'll but it you
________
teen vid

 

[papaof2]

These are *serious* chocolate:

http://www.worldwidechocolate.com/shop_cluizel_72dark.html

http://www.worldwidechocolate.com/shop_cluizel_85dark.html

This is for the chocoholic (my younger daughter gave me this for Christmas a couple of years ago - wonder why?):
http://www.worldwidechocolate.com/shop_cluizel_thepure.html

If your prefer chocolate from a specific plantation (yes, there are subtle differences in cacao from different places), that's available here:
http://www.worldwidechocolate.com/shop_cluizel.html

Smile, have some dark chocolate, and go back to programming your PICAXE with a good taste in your mouth and in better health:
http://www.webmd.com/diet/news/20030827/dark-chocolate-is-healthy-chocolate

John

 

[hippy]

bloomin thing, I'm now having to -5 to receive at 4800 then set back to 0 to send at 2400 to lcd then back to -5 for 4800, at least it's working

is this something the tech guys could tweak?

Hopefully. It's never been explained why the 28X1/40X1 need to be tweaked this way at all.

 

[inglewoodpete]

I haven't had any trouble like this yet (fingers crossed). I'm using a 40X1 (8Mhz) and a 14M (4MHz) with no problems. Short data transfers, though.

 

[ciseco]

Well wouldnt you believe it, the 28x I've been having trouble with, seems no amount of calibfreq will make it work tried +15 through to -15. Anyone got any advice or should I phone tech supplies and ask for a new one?

Miles

John I have just sent you a personal message
________
Ford Transcontinental picture

 

[inglewoodpete]

Do you really mean 28X? That one has no internal resonator to alter with CalibFreq. It requires an external crystal or resonator.

 

[ciseco]

Sorry lazy typing 28x1 with external 4Mhz

Miles
________
marijuana vaporizer

 

[hippy]

When using an external crystal / resonator, the operating frequency will be fixed. No amount of CalibFreq will alter that while running from an external clock source.

You'll need to switch to the internal oscillator if you want to tweak the operating frequency.

 

[Technical]

This could be a ST / TTL input pin issue, if it works on a 40X1 there is no firmware reason why the 28X1 should not work, they are basically the same firmware. Try reducing the PICAXE supply to 4V so that the 3.3V signal form the Xbee is within 0.8 of Vs.

 

[ciseco]

Thamks to technical support I now have it working, just ran the PICAXE at 3.3v off same volreg as the xbee, so it must be a shotky triggered input.

Now having BIG glass of wine, that has been driving me up the wall for weeks

Miles
________
Honda Ascot history

 

[MPep]

What is this ST/TTL thing you mention?

 

[lahaye]

Hello,

TTL: Transistor to Transistor Logic.
ST : Schmidt (or Schmitt?) Trigger.

I am a newb so my knowledge is VERY sketchy so please take the following with a bucket of salt:

TTL indicates the voltage the ICs (Integrated Circuits) can operate on (5V).
It probably indicates more than that but I wouldn't know.
A input will be high at a certain voltage level. (as technical stated 0,8 of Vs [80% of supply voltage])

ST is basically a trigger with hysteresis (for example goes high at 3V and falls back to low at 2V).

[bucket of salt end]



There was a posted thread a month ago by either hippy, dippy or technical that listed how the inputs on different PICAXES ( their corresponding microchip PICs actually) behave, whether they are ST input or TTL inputs. They see the highs and lows in a slightly different fashion, try a forum search, that will explain it far better and accurate then I can.

You might already know all of this already and just struggle with the TLA (three/two letter abbreviations).

regards
Florian

 

[MPep]

Florian,

Bedankt. ("Thanks" in Dutch).
I know TTL, but ST threw me. Just hadn't thought of Schmitt Trigger inputs at all, well certainly not as a seperate Logic Family.

ST I also understand.