"back plane" connection for Atmega128 MLF package

Started by inpactmicro August 4, 2004
Is it absolutely necessary to connect to GRROUND the back plane
connection of the 64 pin MLF package for the ATmega128L package or is
this purely for thermal dissipation. what is the effect of not
connecting this underside pin to Ground?




Hi there, I am trying to interface my EEPROM (24FC128) using TWI. but I cant get ACK from the EEPROM. Can anyone help me? I managed to get 0x08 from EEPROM but fail to get ACK from it after that.

I have wired my A0,A1 and A2 to ground. SCL and SDA to pull-up resistor.
Thanks.
Regards,

Andrew ---------------------------------


I don't know, what programming language you're using, but maybe you want to
take a look at the WinAVR examples explaining the use of the TWI peripherals
in C.

WinAVR can be obtained at www.avrfreaks.net , maybe there's also a separate
download for the TWI examples.

Jan ----- Original Message -----
From: "Andrew Lim" <normaxcite@norm...>
To: <avrclub@avrc...>
Sent: Friday, August 06, 2004 2:45 PM
Subject: [AVR club] Having Problem with TWI using ATmega8535 >
> Hi there, I am trying to interface my EEPROM (24FC128) using TWI. but I
cant get ACK from the EEPROM. Can anyone help me? I managed to get 0x08 from
EEPROM but fail to get ACK from it after that.
>
> I have wired my A0,A1 and A2 to ground. SCL and SDA to pull-up resistor. >
> Thanks. >
> Regards,
>
> Andrew > --------------------------------- >
> Yahoo! Groups Links >




Hi Jan,

I'm using AVR studio 4. Its assembly language. Do u have experience with TWI ? Regards,
Andrew

Jan Weber <jan.weber@jan....> wrote:
I don't know, what programming language you're using, but maybe you want to
take a look at the WinAVR examples explaining the use of the TWI peripherals
in C.

WinAVR can be obtained at www.avrfreaks.net , maybe there's also a separate
download for the TWI examples.

Jan ----- Original Message -----
From: "Andrew Lim" <normaxcite@norm...>
To: <avrclub@avrc...>
Sent: Friday, August 06, 2004 2:45 PM
Subject: [AVR club] Having Problem with TWI using ATmega8535 >
> Hi there, I am trying to interface my EEPROM (24FC128) using TWI. but I
cant get ACK from the EEPROM. Can anyone help me? I managed to get 0x08 from
EEPROM but fail to get ACK from it after that.
>
> I have wired my A0,A1 and A2 to ground. SCL and SDA to pull-up resistor. >
> Thanks. >
> Regards,
>
> Andrew > --------------------------------- >
> Yahoo! Groups Links >


---------------------------------
Yahoo! Groups Links

To
---------------------------------


Hi Andrew,

I have not used TWI yet, but it seems to be quite hard to use.

Jan
----- Original Message -----
From: "Andrew Lim" <normaxcite@norm...>
To: <avrclub@avrc...>
Sent: Saturday, August 07, 2004 4:46 AM
Subject: Re: [AVR club] Having Problem with TWI using ATmega8535 > Hi Jan,
>
> I'm using AVR studio 4. Its assembly language. Do u have experience with
TWI ?
>
>
> Regards,
> Andrew
>
> Jan Weber <jan.weber@jan....> wrote:
> I don't know, what programming language you're using, but maybe you want
to
> take a look at the WinAVR examples explaining the use of the TWI
peripherals
> in C.
>
> WinAVR can be obtained at www.avrfreaks.net , maybe there's also a
separate
> download for the TWI examples.
>
> Jan > ----- Original Message -----
> From: "Andrew Lim" <normaxcite@norm...>
> To: <avrclub@avrc...>
> Sent: Friday, August 06, 2004 2:45 PM
> Subject: [AVR club] Having Problem with TWI using ATmega8535 > >
> > Hi there, I am trying to interface my EEPROM (24FC128) using TWI. but I
> cant get ACK from the EEPROM. Can anyone help me? I managed to get 0x08
from
> EEPROM but fail to get ACK from it after that.
> >
> > I have wired my A0,A1 and A2 to ground. SCL and SDA to pull-up resistor.
> >
> >
> >
> > Thanks.
> >
> >
> >
> > Regards,
> >
> > Andrew
> >
> >
> > ---------------------------------
> >
> >
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> > ---------------------------------
> Yahoo! Groups Links
>
> To >
> --------------------------------- >
> Yahoo! Groups Links >





Hi Everyone,

I'm currently developing RS232 module for my project. I'm using ATmega8535 for RS232 developement. I'm using internal oscilator of 1MHz.

When I set my baud rate to 19.2kbps, I found that the data that I receive has lots of noice. For example if the uC is receiving 'a' and transmit back 'a', I will some times see 'q' on my screen.

However, I have solve it by tweaking the OSCCAL to 0xFF. At the same time, I have read that if my internal OSC is more than 10% of the nomimal frequency, my EEPROM and Flash write may fail (Atmega8535 datasheet pg.28) . If this is the case, how can I solve my RS232 problem and yet still can write to my Flash and EEPROM?
Thanks a lot.
Regards,

Andrew ---------------------------------


For asynchronous serial communication it is better to use a crystal as clock
source. That's what I would do to solve the accuracy problems. Otherwise, a
slight change in ambient temperature could render your device unuseable.

Jan ----- Original Message -----
From: "Andrew Lim" <normaxcite@norm...>
To: <avrclub@avrc...>
Sent: Thursday, August 12, 2004 5:19 PM
Subject: [AVR club] RS232 Baud Rate questions >
> Hi Everyone,
>
> I'm currently developing RS232 module for my project. I'm using ATmega8535
for RS232 developement. I'm using internal oscilator of 1MHz.
>
> When I set my baud rate to 19.2kbps, I found that the data that I receive
has lots of noice. For example if the uC is receiving 'a' and transmit back
'a', I will some times see 'q' on my screen.
>
> However, I have solve it by tweaking the OSCCAL to 0xFF. At the same
time, I have read that if my internal OSC is more than 10% of the nomimal
frequency, my EEPROM and Flash write may fail (Atmega8535 datasheet pg.28) .
If this is the case, how can I solve my RS232 problem and yet still can
write to my Flash and EEPROM?
> Thanks a lot. >
> Regards,
>
> Andrew > --------------------------------- >
> Yahoo! Groups Links >




--- In avrclub@avrc..., Andrew Lim <normaxcite@y...> wrote:

> ... RS232 ... ATmega8535 ...
> internal oscilator of 1MHz.
> ... baud rate to 19.2kbps ...

Let's see. For a bit rate of 19200 you need to set the bit rate
generator for 16 * 19200 which is 307,200 Hz. With 1 MHz in, if you
divide by 3 you get 333,333 Hz, which is 8% high. That's too far off
for start/stop serial communication. You should try to be within 2%.
(If your MCU has a double speed UART you might be in better shape,
but still not close enough.)

Your fiddling with OSCCAL is probably slowing the 1 MHz clock down
enough to make it work, but if you check the data sheet you may find
that the internal clock is not stable enough over voltage and
temperature to keep it working always.

So, I'm afraid I agree that you will need to have a crystal or
ceramic resonator clock source.

We would need to know more about your project to help you pick out
the right part. Is power consumption critical? What about size? Or
did you just go with the internal source for convenience? (My
favorite crystal frequency for ATmegas is 7.3728 MHz.)

Graham.




"Is power consumption critical? What about size? Or
did you just go with the internal source for convenience? (My
favorite crystal frequency for ATmegas is 7.3728 MHz.)"
Hi Graham,

Power consumption is critical for my project. Thats why I'm lowering the clk freq. I have to build my board as small as possible too. The max temp it has to go through will be 65 celcius.

If I switch to external crystal, does it mean that my uC will also use the xternal xtal ? Or I can actually use intercall oscillator for my uC and xternal xtal for RS232 ?

Andrew

Graham Davies <YahooGroups@Yaho...> wrote:--- In avrclub@avrc..., Andrew Lim <normaxcite@y...> wrote:

> ... RS232 ... ATmega8535 ...
> internal oscilator of 1MHz.
> ... baud rate to 19.2kbps ...

Let's see. For a bit rate of 19200 you need to set the bit rate
generator for 16 * 19200 which is 307,200 Hz. With 1 MHz in, if you
divide by 3 you get 333,333 Hz, which is 8% high. That's too far off
for start/stop serial communication. You should try to be within 2%.
(If your MCU has a double speed UART you might be in better shape,
but still not close enough.)

Your fiddling with OSCCAL is probably slowing the 1 MHz clock down
enough to make it work, but if you check the data sheet you may find
that the internal clock is not stable enough over voltage and
temperature to keep it working always.

So, I'm afraid I agree that you will need to have a crystal or
ceramic resonator clock source.

We would need to know more about your project to help you pick out
the right part. Is power consumption critical? What about size? Or
did you just go with the internal source for convenience? (My
favorite crystal frequency for ATmegas is 7.3728 MHz.)

Graham.
---------------------------------
Yahoo! Groups Links

To

---------------------------------


When I was buliding my first computer -- from a manual called "Tezukuzri
Computa-a O Tsukurimasho-o," back when Doctor Dobbs was in mimeo -- I went
to Akihabara to pick up a 4-meg crystal oscillator. Went through the
tunnels, and found the right guy -- "oscillators over there..." -- and he
said (after I paid him something like 125 yen, "Let me just test it.")

He stuck it in some test instrument, and after some fribblering the numbber
came out on the LCD read-out: 4,000,000. Seven significant digits.

Now either he fixed the machine, or he fixed the osclilator he was about to
sell me, or he performed a bit of pristadigitateurisme.

Whichever. Damn, but thank the world for Akiharbara.

-dlj.

>From: "Jan Weber" <jan.weber@jan....>
>Reply-To: avrclub@avrc...
>To: <avrclub@avrc...>
>Subject: Re: [AVR club] RS232 Baud Rate questions
>Date: Thu, 12 Aug 2004 20:07:55 +0200
>
>For asynchronous serial communication it is better to use a crystal as
>clock
>source. That's what I would do to solve the accuracy problems. Otherwise, a
>slight change in ambient temperature could render your device unuseable.
>
>Jan >----- Original Message -----
>From: "Andrew Lim" <normaxcite@norm...>
>To: <avrclub@avrc...>
>Sent: Thursday, August 12, 2004 5:19 PM
>Subject: [AVR club] RS232 Baud Rate questions > >
> > Hi Everyone,
> >
> > I'm currently developing RS232 module for my project. I'm using
>ATmega8535
>for RS232 developement. I'm using internal oscilator of 1MHz.
> >
> > When I set my baud rate to 19.2kbps, I found that the data that I
>receive
>has lots of noice. For example if the uC is receiving 'a' and transmit back
>'a', I will some times see 'q' on my screen.
> >
> > However, I have solve it by tweaking the OSCCAL to 0xFF. At the same
>time, I have read that if my internal OSC is more than 10% of the nomimal
>frequency, my EEPROM and Flash write may fail (Atmega8535 datasheet pg.28)
>.
>If this is the case, how can I solve my RS232 problem and yet still can
>write to my Flash and EEPROM?
> >
> >
> >
> > Thanks a lot.
> >
> >
> >
> > Regards,
> >
> > Andrew
> >
> >
> > ---------------------------------
> >
> >
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
>

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