Re: UART connection between ATSAMD20 and ATtiny4313

From	Grant Edwards <invalid@invalid.invalid>
Newsgroups	comp.arch.embedded
Subject	Re: UART connection between ATSAMD20 and ATtiny4313
Date	2023-04-26 21:00 +0000
Organization	PANIX Public Access Internet and UNIX, NYC
Message-ID	<u2c3d0$l35$1@reader2.panix.com> (permalink)
References	<u2be3n$1a5nq$1@dont-email.me> <u2bhl1$1em9g$1@dont-email.me> <u2c27u$1hfgr$1@dont-email.me>

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On 2023-04-26, pozz <pozzugno@gmail.com> wrote:

> ATtiny4313 datasheet[1] says the internal oscillator is factory 
> calibrated with an accuracy of +/-10% at Vcc=3V and 25°C temperature.

10% total error (combination of both ends) is pretty much right at the
limit according to the usual rule of thumb for UART receivers that
sync only on the start bit. IIRC, there used to be UART receivers that
would sync on every edge within the data "word" as well, but I don't
think that was ever very common -- and to take advantage of it, you
had to make sure your data had edges. :)

Can you spare a line for a clock and go synchronous? (Or are they
really UARTs and not USARTs?).

> This accuracy can be reduced to +/-2% at a fixed voltage and a fixed 
> temperature with a user calibration.

2% is no problem at all. With a crystal on the other end, you should
be able to easily tolerate +/-5%. The requirement for a fixed
temperature, OTOH, is usually a problem.

> I could calibrate for a fixed voltage (3.3V), but I can't fix a 
> temperature, because it can vary in the real application.

Does the ATtiny have an on-die temp sensor? If yes, you could try
characterizing the oscillator over temperature at 3.3V and adjusting
the baud rate divisor as the temperature changes. That get's expensive
if you have to do it on every unit during production, but if the T/F
curve is consistent enough between units, then maybe...

Thread

UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-04-26 16:56 +0200
  Re: UART connection between ATSAMD20 and ATtiny4313 David Brown <david.brown@hesbynett.no> - 2023-04-26 17:57 +0200
    Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-04-26 22:40 +0200
      Re: UART connection between ATSAMD20 and ATtiny4313 Grant Edwards <invalid@invalid.invalid> - 2023-04-26 21:00 +0000
        Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-04-26 17:20 -0700
        Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-04-27 10:15 +0200
  Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-04-26 09:26 -0700
    Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-04-26 22:44 +0200
      Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-04-26 17:10 -0700
        Re: UART connection between ATSAMD20 and ATtiny4313 David Brown <david.brown@hesbynett.no> - 2023-04-27 09:17 +0200
        Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-04-27 10:28 +0200
          Re: UART connection between ATSAMD20 and ATtiny4313 Andrew Smallshaw <andrews@sdf.org> - 2023-04-27 13:28 +0000
            Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-04-27 09:22 -0700
              Re: UART connection between ATSAMD20 and ATtiny4313 David Brown <david.brown@hesbynett.no> - 2023-04-28 09:48 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-04-28 01:55 -0700
            Re: UART connection between ATSAMD20 and ATtiny4313 Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2023-04-27 20:18 +0300
              Re: UART connection between ATSAMD20 and ATtiny4313 Ulf Samuelsson <ulf.r.samuelsson@gmail.com> - 2023-04-27 23:03 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2023-04-28 09:58 +0300
              Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-04-27 17:45 -0700
                Re: UART connection between ATSAMD20 and ATtiny4313 Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2023-04-28 10:00 +0300
                Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-04-28 00:21 -0700
                Re: UART connection between ATSAMD20 and ATtiny4313 Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2023-04-28 11:43 +0300
                Re: UART connection between ATSAMD20 and ATtiny4313 Ulf Samuelsson <ulf.r.samuelsson@gmail.com> - 2023-04-28 11:10 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2023-04-28 17:26 +0300
                Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-04-28 02:14 -0700
                Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-04-28 02:19 -0700
                Re: UART connection between ATSAMD20 and ATtiny4313 David Brown <david.brown@hesbynett.no> - 2023-04-28 14:51 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-04-28 16:41 -0700
                Re: UART connection between ATSAMD20 and ATtiny4313 David Brown <david.brown@hesbynett.no> - 2023-04-29 18:01 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-04-30 02:37 -0700
          Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-04-27 09:02 -0700
            Re: UART connection between ATSAMD20 and ATtiny4313 David Brown <david.brown@hesbynett.no> - 2023-04-28 15:01 +0200
              Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-04-28 16:44 -0700
                Re: UART connection between ATSAMD20 and ATtiny4313 David Brown <david.brown@hesbynett.no> - 2023-04-29 17:59 +0200
  Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-05-03 18:16 +0200
    Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-05-03 09:40 -0700
      Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-05-04 10:34 +0200
        Re: UART connection between ATSAMD20 and ATtiny4313 David Brown <david.brown@hesbynett.no> - 2023-05-04 12:31 +0200
          Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-05-05 10:51 +0200
            Re: UART connection between ATSAMD20 and ATtiny4313 David Brown <david.brown@hesbynett.no> - 2023-05-05 12:59 +0200
              Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-05-05 18:01 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 Dimiter_Popoff <dp@tgi-sci.com> - 2023-05-05 19:52 +0300
                Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-05-07 23:20 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-05-05 11:37 -0700
                Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-05-07 23:21 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 David Brown <david.brown@hesbynett.no> - 2023-05-08 08:37 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-05-08 09:24 +0200
            Re: UART connection between ATSAMD20 and ATtiny4313 Grant Edwards <invalid@invalid.invalid> - 2023-05-05 20:16 +0000
              Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-05-07 23:17 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-05-07 14:27 -0700
                Re: UART connection between ATSAMD20 and ATtiny4313 David Brown <david.brown@hesbynett.no> - 2023-05-08 08:34 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 Dimiter_Popoff <dp@tgi-sci.com> - 2023-05-08 13:46 +0300
                Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-05-08 09:38 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 Grant Edwards <invalid@invalid.invalid> - 2023-05-08 14:12 +0000
                Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-05-08 18:13 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-05-08 11:39 -0700
                Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-05-09 17:04 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-05-09 14:32 -0700
                Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-05-10 08:55 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 Grant Edwards <invalid@invalid.invalid> - 2023-05-08 19:09 +0000
                Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-05-09 17:08 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-05-08 07:32 -0700
                Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-05-08 18:27 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-05-08 11:52 -0700
                Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-05-09 16:52 +0200
                Re: UART connection between ATSAMD20 and ATtiny4313 Grant Edwards <invalid@invalid.invalid> - 2023-05-09 15:10 +0000
                Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-05-09 14:29 -0700
        Re: UART connection between ATSAMD20 and ATtiny4313 Rick C <gnuarm.deletethisbit@gmail.com> - 2023-05-04 06:21 -0700
          Re: UART connection between ATSAMD20 and ATtiny4313 pozz <pozzugno@gmail.com> - 2023-05-05 11:02 +0200

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