Confused over A/D settings

[malc-c]

In reference to this thread http://www.picbasic.co.uk/forum/showthread.php?t=12714 I still can't get the A/D conversion working when porting the code from 16F877A to an 18F4550.

For some reason the following code work on the 16F877A but not the 18F4550

DEFINE ADC_BITS 10                ' Set-up ADC for fastest 10-bit results
DEFINE ADC_CLOCK 2
DEFINE ADC_SAMPLEUS 5
INCLUDE "DT_Analog.pbp"

MaxSetPoint  CON 350              ' Pot fully clockwise
MinSetPoint  CON 100              ' Pot fully counter clockwise 
ADbits = 14                       ' set A/D resolution to 14-bits
CMCON = 7                         ' disable Comparators
ADCON1 = %10000010                ' AN0-4 Analog, Right justify
ADCON1 = $0F

I've checked the datasheet and read a section on A/D from one of my PbP project books, and if I've read it correctly the ADCON1 = %10000010 should set the register up as output right justified (bit 7 set to 1), AN7-AN5 digital, AN4-AN0 analogue, Vref+=vdd and Vref-=Vss.

However it then has the line ADCON1 = $0F which (from googling) sets all pins to digital... OK fair enough I though, simply comment out this line, however when I do this all I get on the LCD display is a row of squares on the top row, which flash as the PIC is performing the rest of the functions (PID calculations etc). If I then uncomment the ADCON1=$0F line the temperatures from all the probes (which are on port D) are displayed. It is as if ADCON1 is setting all pins on all ports to digital

[Darrel Taylor]

Skip the "PBP Project book".

Have another look at the datasheet for an 18F4550.
http://ww1.microchip.com/downloads/e...Doc/39632e.pdf
Page 266, Register 21-2 ADCON1

ADCON1 = %00001011

Also notice that the ADFM bit isn't in ADCON1 anymore.

ADCON2.7 = 1

[malc-c]

Cricky... you're up late !

Thanks again.... one day I'm hoping all this will click and I'll understand these subtle differences in the different PICs !

[malc-c]

Well that's fixed... now able to set the temps by the pots..



Just need to work out why the outputs have stopped working, especially when the PID should be resulting in a value above zero ....