adc trouble with 16f628A

[Goos_E]

when i try to compile a basic program that reads ADC0 then i got a popup saying that this microcontroller doesn't feature a/d converter module. but when i read the 40044 pdf file from microchip that says there are 2 analog comperator modules present. What am i doing wrong.

 

[geko]

The PIC16F628A doesn't have an ADC module. The Comparator module has analogue inputs but it is not an Analogue-to-Digital-Convertor (ADC)

 

[Goos_E]

what is a comperater module that has analog input. (sorry for my dumb question)

 

[geko]

Well it's a Comparator - a comparator is a device that compares two voltages and switches its output to indicate which is larger. In repsect of the 16F628A it is described in section 10 of the datasheet.

 

[ericgibbs]

what is a comperater module that has analog input. (sorry for my dumb question)

hi
This code is a simple demo of the 628A comparators, it will run Oshonsoft

Its been copied from here.
https://www.electro-tech-online.com/threads/code-snippets-for-the-oshonsoft-basic-compiler.112540/

27Nov2010 for Oshonsoft IDE
'PIC 16F628/A COMPARATOR DEMO.

'Demo mode of comparator set for 4 analog channel inputs PA0.1.2.3
'displays the greater than/ less than Vref states of CMCON.7 and .6
''
'During tests, the comparision switch over is approx 5 to 10mV
E

'for Sim only
Define SIMULATION_WAITMS_VALUE = 1
 
Dim temp1 As Word
Dim vref1 As Word
Dim vrhi As Word
Dim vrlo As Word
 
'LCD assignments
Define LCD_LINES = 4
Define LCD_CHARS = 16
Define LCD_BITS = 4
Define LCD_DREG = PORTB
Define LCD_DBIT = 4
Define LCD_RSREG = PORTB
Define LCD_RSBIT = 1
Define LCD_EREG = PORTB
Define LCD_EBIT = 2
 
'make AN0,,1,2,3 as Inputs
TRISA = %00001111
 
TRISB = %00000000  'outputs
 
'comparator settings
CMCON.C2OUT = 0
CMCON.C1OUT = 0
CMCON.C2INV = 1
CMCON.C1INV = 1
CMCON.CIS = 0  'comparator selection PA.0/1 to PA.3/2
 
CMCON.CM2 = 0  'mode set for internal Vref connected
CMCON.CM1 = 1
CMCON.CM0 = 0
 
'Vref settings
VRCON.VREN = 1
VRCON.VROE = 0
 
VRCON.VRR = 0  'select Vref low=1 or Vref high =0
VRCON.VR3 = 1  'Vref 2^3 bit
VRCON.VR2 = 1
VRCON.VR1 = 1
VRCON.VR0 = 1  'Vref 2^0 bit
 
Lcdinit
 
'this section converts the binary to decimal value of the Vref settings
'as selected by Vr3,2,1,0 , decimal 0 thru 15
If VRCON.VR3 = 1 Then
temp1 = 8
Endif
If VRCON.VR2 = 1 Then
temp1 = temp1 + 4
Endif
If VRCON.VR1 = 1 Then
temp1 = temp1 + 2
Endif
If VRCON.VR0 = 1 Then
temp1 = temp1 + 1
Endif
 
'* 1000 to allow for lack of decimal fractions
temp1 = temp1 * 1000
 
'test if in Low or High range of Vref options
If VRCON.VRR = 1 Then  'low range
temp1 = (temp1 / 24) * 5
vrhi = temp1 / 1000
vrlo = (temp1 - (vrhi * 1000)) / 10
Else  'high range
temp1 = 1250 + ((temp1 / 32) * 5)
vrhi = temp1 / 1000
vrlo = (temp1 - (vrhi * 1000)) / 10
Endif
 
'show on LCD line 1
Lcdout "Vref= ", #vrhi, "." #vrlo
 
'above Vref value displayed once only
 
 
main:
 
CMCON.CIS = 0
Lcdcmdout LcdLine3Home
 
'test for IF PORTA.0 is  > or < than Vref, display result
If CMCON.6 = 1 Then
Lcdout "A.0>Vr"
Else
Lcdout "A.0<Vr"
Endif
 
Lcdcmdout LcdLine3Pos(10)
 
'test for IF PORTA.1 is  > or < than Vref
If CMCON.7 = 1 Then
Lcdout "A.1>Vr"
Else
Lcdout "A.1<Vr"
Endif
 
'switch from PA.0 and PA.1 to  PA.3 and PA.2 analog inputs
CMCON.CIS = 1
 
'repeat the Vref for PA.3 and PA.2 , display result
Lcdcmdout LcdLine4Home
If CMCON.7 = 1 Then
Lcdout "A.2>Vr"
Else
Lcdout "A.2<Vr"
Endif
 
Lcdcmdout LcdLine4Pos(10)
If CMCON.6 = 1 Then
Lcdout "A.3>Vr"
Else
Lcdout "A.3<Vr"
Endif
 
Goto main

 

[Goos_E]

Thank you very much, I got it. It's a analog Comperator instead of ADC

 

[ericgibbs]

Thank you very much, I got it. It's a analog Comperator instead of ADC

hi
There are ways of using the 16F628A as an A2D.

Its a Resistor/Capacitor discharge method that times the discharge of the capacitor in order to determine the input voltage.

I do not have a code example, but it has been discussed on these Forums.

E.