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Date: Wed, 17 Feb 2016 15:23:42 +0000
Message-ID: <CAA8k23SSF0vfOaRgwU_56yFmksVYLsZ-yfGpFvP9=-LEDCxHCA@mail.gmail.com>
From: Andy Talbot <andy.g4jnt@gmail.com>
To: rsgb_lf_group@blacksheep.org, rsgb_lf_group@yahoogroups.co.uk
Subject: Re: LF: PIC-based GPSDO with A/D converter / supported serial
 baudrates ?
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I've just made some tests on the FTDI232 chip at high baud rates.

Using a custom routine written in  PowerBasic (CC) , I used that language's
own interpretation and interface to the driver to pass arbitrary baud rates
to the chip.   With the device set for 8 data,  1 stop bit and no
parity, I repeatedly send the character 0x55 in a continuous loop.  This
pattern of bits, if sent contiguously (characters are sent LSB first)
 should therefore result in a square wave being generated at a frequency
exactly equal to half the specified baud rate.

The FTDI232 data sheet states that baud rates are determined based on a
3MHz input to a divisor of (N + M/8, where N =3D 2 to 16384, plus two speci=
al
cases on N =3D 0 and N =3D 1 for  3Meg and 1Meg rates respectively.   This
setting is hidden from my application, and happens transparently based on
the baud rate I specify beign passed to the driver via PowerBasic.

The following results were obtained :

Requested         Frequency
Baud rate           Generated

1M                     500000
2M


On 12 February 2016 at 17:59, Wolfgang B=C3=BCscher <dl4yhf@freenet.de> wro=
te:

> Thanks Andy. I wanted to keep it simple (but not necessarily stupid), by
> using available hardware. In my case, the dreadful (and, most likely,
> "faked") Prolific USB <-> RS232 adapter.
>
>

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<div dir=3D"ltr"><div>I&#39;ve just made some tests on the FTDI232 chip=C2=
=A0at high baud rates.</div><div><br></div><div>Using a custom routine=C2=
=A0written in=C2=A0=C2=A0PowerBasic (CC) , I used that language&#39;s own i=
nterpretation and interface to the driver to pass arbitrary baud rates to t=
he chip.=C2=A0=C2=A0 With the device set for 8 data, =C2=A01 stop bit and n=
o parity,=C2=A0I=C2=A0repeatedly send the character 0x55 in a continuous lo=
op.=C2=A0 This pattern of bits, if sent contiguously (characters are sent L=
SB first) =C2=A0should therefore result in a square wave being generated=C2=
=A0at a=C2=A0frequency exactly equal to=C2=A0half the specified baud rate.<=
/div><div><br></div><div>The FTDI232 data sheet states that baud rates are =
determined based on a 3MHz input to a divisor of (N + M/8, where=C2=A0N =3D=
 2 to 16384, plus two special cases on N =3D 0 and N =3D 1 for=C2=A0 3Meg a=
nd 1Meg rates respectively.=C2=A0=C2=A0 This setting is hidden from my appl=
ication, and happens transparently based on the baud rate I specify beign p=
assed to the driver via PowerBasic.=C2=A0 </div><div><br></div><div>The fol=
lowing results were obtained :</div><div><br></div><div>Requested=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Frequency</div><div>Baud rate=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Generated</div><div>=
<br></div><div>1M=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 =C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 500000</div><div>=
2M</div><div><br></div><div><br></div><div class=3D"gmail_extra"><br><div c=
lass=3D"gmail_quote">On 12 February 2016 at 17:59, Wolfgang B=C3=BCscher <s=
pan dir=3D"ltr">&lt;<a href=3D"mailto:dl4yhf@freenet.de" target=3D"_blank">=
dl4yhf@freenet.de</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote=
" style=3D"margin:0px 0px 0px 0.8ex;padding-left:1ex;border-left-color:rgb(=
204,204,204);border-left-width:1px;border-left-style:solid">
 =20
   =20
 =20
  <div bgcolor=3D"#FFFFFF" text=3D"#000000">
    Thanks Andy. I wanted to keep it simple (but not necessarily
    stupid), by using available hardware. In my case, the dreadful (and,
    most likely, &quot;faked&quot;) Prolific USB &lt;-&gt; RS232 adapter.<b=
r>
=C2=A0=C2=A0=C2=A0 </div></blockquote></div><br></div></div>

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