I should have been a little more clear. If you want something reliable, external oscillator is a must. Being that serial communications are involved. The internals work fine but sometimes the timing will get a little off.

The oscillator you choose will need to be defined in the *.inc file for the chip you are using along with the other fuses. In the *.bas file you tell PBP what the oscillator speed is for timing. These are the same yet different.

You will find a line in the *.inc file something like this.

__config _XT_OSC & _WDT_ON & _PWRTE_ON & _BODEN_ON & _LVP_OFF & _CP_OFF

Look at the data sheet and it will tell you what each one does.