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pinguino sin cristal?
28-11-2013, 01:58 AM,
pinguino sin cristal?
Hace tiempo que veo que hay bootloaders para pinguinos a 8Mhz y creo que los chips tienen un oscilador o cristal interno de 8Mhz.¿ Es posible montar un pinguino sin cristal?
si es asi solo seria cargar el bootloader adecuado y quitar el crsital con los 2 condensadores? funcionaria sin estar conectado al usb?


PD. alguien sabe donde ver los cambios en cada bootloader? es que salen vastantes y me gustaria saber que cambia.
08-12-2013, 01:35 AM,
RE: pinguino sin cristal?
Me contesto a mi mismo.

No se puede si es necesario usar el USB, Porque el USB necesita una frecuencia de 48Mhz y solo se puede alcanzar con un multiplicador que solo actua cuando hay un cristal externo. Mas o menos es eso lo que he entendido de este link
09-12-2013, 08:26 PM,
RE: pinguino sin cristal?
se puede utilizar el 18f45k50 o la 1825k50, usando el bootloader 4.14 INTOSC :-)

10-12-2013, 10:27 AM,
RE: pinguino sin cristal?
"It has been reported" that the J50/J53 PICs' internal clock is "somewhat" sufficient for USB "under lab conditions". Given this, for, say, a quick hardware hack, you may TRY the particular _INTOSC bootloader version (i.e. for those where you can find one) without external crystals. But for reliable, stable designs, the external crystal should NOT be dropped at all. Even for scenarios, where USB is solely needed in the "very rare case" of a firmware update or alike, it can NOT be recommended without harming one's peace of conscience. Note that this does NOT apply to the K50 PICs: Those can use USB crystal-less "from design"!

Please be aware, that in general, different clock values require different load capacitors, and, moreover, that the clock-depending load capacitances given in microchip documents are more or less general recommendations and, in order to "do it right", you should carefully consider influences like parasitic capacitance, strip line length, geometry, cutting direction and other properties of the crystal itself .. Don't get me wrong: In 99,7% of all use cases it will work, even completely without load capacitors. But in order to get 100% sure (or else be able to blame the manufacturers) that it will work, say, even in a car at -20 or +80 centigrades and with ALL possible combinations of controller and crystal, you would have to do this. Not that this would bother anyone HERE. But maybe worth knowing. (Sorry for replying in English.)
12-12-2013, 05:59 PM,
RE: pinguino sin cristal?
Gracias a los 2.
Se me ocurre otra pregunta relacionado con los cristales. y es que si el un ponguino con un cristal de 8Mhz es mas lento que con uno de 40Mhz, supongo que si, pero como los procesadores de ordenador usan multiplicadores... pues no se si el pic tambien lo hara.
y si el pinguino con un cristal de 40Mhz va mas rapido eso se nota en las lecturas analogicas?


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