First, my oscillator. I have been using the 16F887's internal oscillator. I think if I do nothing my prescaler is set at 4:1. The PIC has an 8mhz internal oscillator. Figure 4-1 on Page 61 of DS41291F (the x887 gospel) indicates that by setting OSCCON = %01110111 I can get the internal 8mhz oscillator and the prescaler of 1:1. Does this seem correct to you all? I will try this evening.

What do I need circuit-wise to implement the 20Meg external crystal oscillator?

Second, the placement of my forward looking SRF05. I thought I found that slanting them to the left just a bit makes less possible reflection from the side wall coming into the front pingers. That seemed to work on the bench, but again confusion in the real world. I have not thought through what the side pingers should be hearing while the car is turning left. For racing I have moved the desired track out to 24 inches away from the side wall.

Using a carpenters measuring stick I have calibrated my pingers. They seem consistent (again on my bench).

Ken