setup_adc divide by 64?

[Phil_P]

Hi there,
Using the 16F877A device, by setting the correct bit-pattern in ADCON0 & ADCON1, apparently the ADC conversion-time can be set to Fosc/64.
The header file does not have a define for Fosc/64 as the parameter in setup_adc, anybody know what the value for this is?
Cheers,
Phil

[Ttelmah]

It should be in the header file. What compiler version have you got?. In 3.249, it is there as ADC_CLOCK_DIV_64. It is there back in 3.221. However it is missing in 3.191.

If your compiler is this old, there may well be other problems. The definition format was changed for the latter compilers, to give access to the extra bit needed for this (the old setup, only adjusted ADCS1, and ADCS0). Try:
#define ADCS2ON 0x40

Then
SETUP_ADC_PORTS(ALL_ANALOG | ADCS2ON);

Change the 'ALL_ANALOG' selection, to whatever one you need to select your required analog inputs, and then use:

SETUP_ADC(ADC_CLOCK_DIV_32);

Basically the pattern needed, is the same in the port controlled by 'setup_adc', as required for /32, but needs the extra bit set in the ADCON1, to select /64. ADCON1, is the port used to set which inputs are enabled, and the extra bit corresponds to the '0x40' pattern defined above. If this doesn't work, you'll have to go 'manual', and control the ports yourself.

Best Wishes

[Phil_P]

I think I have quite an old compiler, but thanks for this advice - makes sense and should work!!
Thank you :-)