AVR-Chat

I'm trying to debug a line-powered AT90PWM3 (yay motors.  Code works 
*mostly*) application.  I need to go beyond "debug by printf", so I 
think I need to get another piece besides the STK500....

Can I use (I guess in order of preference, but correct me if I should 
prefer different ones):
  1. AVR JTAG/ICE/USB, at 
http://microcontrollershop.com/product_info.php?
cPath=110_161&products_id=938

It's isolated (so they say...), but can I use it in AVR Studio / IAR?

  2. A AVR Dragon (I'll build my own optoisolators) [digikey]
  3. JTAG ICE (mk 1) [fleabay]
  4. JTAG ICE mk II  [digikey]

I think I did something funny with the power sequencing, so when I 
changed compilers the board isn't coming up under IAR (works kinda on 
GCC, but the control loops aren't behaving right).

Grab AVRCalc off the projects section.
If your oscillator was exactly 8MHz, the error at 38400 is small. I
don't know what's involved in calibrating the on-board oscillator and
how it's affected by temperature or Vcc changes.

--- In AVR-Chat@yahoogroups.com, "Cat" <catalin_cluj@...> wrote:
>
> Hi,
> 
> What serial speed (RS232) can I achieve using the built-in oscilator, 
> running at 8MHz?
> 
> I'm using the "Fleury" serial library, but it looks like I can't go
above 
> 38400bps...
> 
> would this be because the RC clock is not precise enough, or because
8MHz is 

> not fast enough to go above 38400?
> 
> Thanks,
> 
> Cat
>

At 06:02 AM 31/05/2007, you wrote:
>   2. A AVR Dragon (I'll build my own optoisolators) [digikey]
>   4. JTAG ICE mk II  [digikey]

These would be the only ones that would work as they have
debugWire facility, just checked and the Dragon supports the chip
(~US$49). I believe that there is a sale for the JTAGMK2 at about
half the usual price of ~US$299)

Regards

John Samperi

********************************************************
Ampertronics Pty. Ltd.
11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
Tel. (02) 9674-6495       Fax (02) 9674-8745
Email: john@ampertronics.com.au
Website  http://www.ampertronics.com.au
*Electronic Design * Custom Products * Contract Assembly
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Hi,

What serial speed (RS232) can I achieve using the built-in oscilator, 
running at 8MHz?

I'm using the "Fleury" serial library, but it looks like I can't go above 
38400bps...

would this be because the RC clock is not precise enough, or because 8MHz is 
not fast enough to go above 38400?

Thanks,

Cat

On 5/30/07, stevech11 <stevech@san.rr.com> wrote:
> Grab AVRCalc off the projects section.
> If your oscillator was exactly 8MHz, the error at 38400 is small. I
> don't know what's involved in calibrating the on-board oscillator and
> how it's affected by temperature or Vcc changes.


Generally speaking, you need at least a resonator, or crystal, to do
accurate baud rates.
You have to factor in ALL the error sources.  First you have to allow
the other device at least half of the error budget, then figure your
divisor error, then min and max tolerance on the clock.
When you add it all up, the internal RC isn't good enough for serial.

One technique I've used with great success in RC
oscillator Nitron devices is  to use the target to
itself calibrate the half-bit delay loop.I get the
target to send $7F to the micro at the start of the
serial session. The serial line is low for exactly
one-bit period, which is used to set the internal
delay count variable (in EEPROM). Then the micro will
send at the detected bit-rate.
Note that this also gives auto-baud detect including
for non-standard baud rates.

Cheers,
Samir.

--- David VanHorn <microbrix@gmail.com> wrote:
> Generally speaking, you need at least a resonator,
> or crystal, to do accurate baud rates.
> You have to factor in ALL the error sources.  First
> you have to allow the other device at least half
> of the error budget,then figure your
> divisor error, then min and max tolerance on the
> clock. When you add it all up, the internal RC
> isn't good enough for serial.



       
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