From: John Lawton <piclist@jle.co.uk>
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Date: Tue, 20 Oct 2020 10:46:45 -0700
Subject: Re: [PIC] Crystal frequency selection
Thread-Topic: [PIC] Crystal frequency selection
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Well not that specifically, but the datasheet mentioned:

3.6864MHz, 11.0592MHz, 18.432MHz for 0% error @ 115.2kBaud

J



On 20/10/2020 18:11, Neil wrote:
> The 14.7456 crystal?
>
>
>
>
> On 10/20/2020 1:00 PM, John Lawton wrote:
>> But you didn't, it's all there is the datasheets :)
>>
>> John
>>
>> On 20/10/2020 17:34, Neil wrote:
>>> Okay, I found one... 14.7456Mhz crystal --> 59.9824Mhz Fosc, which is
>>> close enough to 64Mhz.
>>> Using SPBRG =3D 127 with that gives me spot-on 115,200 baud (so 0% erro=
r).
>>> And there are 10+ suppliers for 3.2 x 2.5mm SMD crystals with that
>>> frequency so that's common enough to be low-cost and not have to worry
>>> about being discontinued in the near future.
>>> Wish I didn't have to trial and error this though.
>>>
>>> Cheers,
>>> -Neil.
>>>
>>>
>>>
>>>
>>>
>>> On 10/20/2020 12:27 PM, Neil wrote:
>>>> I had also created my own, but it's been trial-and-error (xtal freq
>>>> and SPBRG value) to find a spot-on crystal.
>>>> Now, if your spreadsheet runs through DIgikey's crystal frequency
>>>> selections and picks the spot-on option for me, then you have my
>>>> attention :)
>>>>
>>>> Cheers,
>>>> -Neil.
>>>>
>>>>
>>>>
>>>> On 10/20/2020 12:08 PM, Nicola Perotto wrote:
>>>>> Hi Neil & all,
>>>>> I use the attached spreadsheet to calculate baud and errors.
>>>>> Enter values in yellow cells.
>>>>>          N
>>>>>
>>>>>
>>>>> On 20/10/2020 16:42, Neil wrote:
>>>>>> A bit academic, but this is bugging me... I was trying to get as clo=
se
>>>>>> to 115,200 baud on a PIC18F running at 64Mhz (or thereabouts).
>>>>>> At 64Mhz, best I can get is 0.8% error using SPBRG=3D34.
>>>>>> Calculating backwards, to get exactly 115,200, I can't find an "exac=
t"
>>>>>> crystal.
>>>>>> Shouldn't I be able to find one of those "odd" values to get exactly
>>>>>> 115,200 baud at around 64Mhz?
>>>>>>
>>>>>> Cheers,
>>>>>> -Neil.
>>>>>>

--=20
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