Hmm, hes using; "18F4620., cellular modem at 9600, LCD display and communication to a RTC via I2C." all of that sounds farily expensive. Just add a $1 xtal to drive the PIC at a stable baudrate.
It would be sheer lunacy to pay for all of those peripherals and then try to save the cost of a xtal and use the internal osc for something that needs reliable comms at a "temperature range of -30 to +60C.".
Hmm, hes using; "18F4620., cellular modem at 9600, LCD display and communication to a RTC via I2C." all of that sounds farily expensive. Just add a $1 xtal to drive the PIC at a stable baudrate.
It would be sheer lunacy to pay for all of those peripherals and then try to save the cost of an xtal and use the internal osc for something that needs reliable comms at a "temperature range of -30 to +60C.".
I agree. I'm new to PIC's, I'm more trying to understand whats going on under the hood than save a buck. The only reason I was considering the internal osc. was to eliminate three components and simplify the design, not for the cost of the parts.
The point of my post was to determine if, based upon folks actual experience, using the internal osc creates comm problems at 9600 baud.
Same with choosing a xtal that's not an even divisor of the baud rate, yes there is error created, but does it actually cause problems in real equipment?
In example, networking cable; (CAT5), I've seen all kinds of kludged together installations (long runs, untwisted wire at the terminations, flying splices with wire nuts, etc) which, according to the specs and everything you read, should never work, but in real life generally do.