I2c, srf02, 16f688 -> ultrasonic rangefinder

[Bruce]

You want to write directly to ADCON1 so you have at least Fosc/8 for 4MHz.

ADCIN doesn't do this for you - so your AD conversion clock is way too fast with ADCON1 = 0 by default.

[RussMartin]

You want to write directly to ADCON1 so you have at least Fosc/8 for 4MHz.

ADCIN doesn't do this for you - so your AD conversion clock is way too fast with ADCON1 = 0 by default.

Thanks, Bruce.

I've used ADC with other devices (12F683; 16F88; 16F1827) and always gotten by with the RC clock.

Can I use DEFINE ADC_CLOCK 1? Or if I use ADCON1=%00010000, do I simply omit the DEFINE?

[Bruce]

Hi Russ,

DEFINE ADC_CLOCK xx only works if the clock select bits are in ADCON0, so just write directly to ADCON1 to set the conversion clock. ADCON1 = %00110000 for RC, ADCON1 = %00010000 for Fosc/8 (recommended).