On Tue, 15 Apr 2014, Matt Bennett wrote:

> On Mon, April 14, 2014 10:04 pm, Larry Bradley wrote:
>> Just got one the other day.
>>
>> They use the internal RC oscillator. The 24F chip has a basic 8 mHz
>> clock, rated at 0.25% accuracy, I think. There is an on-board PLL for
>> the USB port that gets you higher clock rates.
>
> The internal FRC on the PIC24FJ64GB002 is +1%, -1.25% max, 0.25% typical.
> This usually isn't good enough for asynchronous comms- while it may work
> *most* of the time, you need to be aware that it could get out of spec.
> The rule of thumb I use is that the baud rate error could be 10x the cloc=
k
> error (since there are 10 bit-times in a standard N81 serial stream).

Not to rain on anyone's parade, but you can get reliable async comms with=20
low accuracy clocks if you send ***LESS*** bits. Just don't use the top=20
bits of each byte and pack your message into the bits you can rely on=20
(the lower ones).

Regards
Sergio Masci
--=20
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