PIC16F1788 ADC Patch

[Chuck Hellebuyck]

I saw that GCB had support for the new PIC16F1788 so I decided to test it on my CHIPINO module. Everything seemed to work fine except ADC.
It would report a constant zero no matter what the voltage was on the ADC pin.
So I pulled up the data sheet and saw the 16F1788 added a Differential Channel Selection feature allowing the negative reference to come from a pin other than -Vref.
This added a setup to the ADCON2 register and unfortunately defaults to the AN0 pin instead of defaulting to the ADNREF setting.

So I added one line to the top of my program to set the ADCON2 to the ADNREF setting.

ADCON2 = 15 

Fortunately this worked perfect and the ADC is working again.

Maybe Hugh or Evan can fix this in a future update.
Until then, this simple one line patch seems to fix the issue.

Here is the simple code example I tested using the PICkit 2 USART Terminal window for communication.

'This program reads the potentiometer on AN0 and Serially sends results to PICkit 2  
'USART terminal. Using the CHIPINO module with 16 MHz Crystal. 

'Chip Settings 
#chip 16F1788,16 

'Serial settings 
#define SerInPort PORTB.6 
#define SerOutPort PORTB.7 
#define SendAHigh Set SerOutPort off 
#define SendALow Set SerOutPort on 
#define RecAHigh SerInPort off 
#define RecALow SerInPort on 

'Set pin directions 
Dir SerOutPort Out 
Dir SerInPort In 

InitSer 1, r9600, 1+WaitForStart, 8, 1, none, invert 

ADCON2 = 15 ' Set Negative Reference Setting to ADNREF in ADCON1 

Start: 
SerPrint 1, "AN0 Reading: " 
SerPrint 1, ReadAD(AN0) 
SerSend 1, 13 
SerSend 1, 10 

goto Start 

[Anobium]

Good work, added to the list. :-)