Battery monitoring - ever tried AN1072?

[flotulopex]

I still would like to know how to "read" the 0,6V (VP6) channel. This voltage reference is provided by the PIC itself.

If I set the ADSCON0 register to (i.e.) %10110100 (right just., VDD, 0,6V Reference, ADC is ON), what is the PICBASIC command to read that channel? If it is ADCIN, then ADCIN what?



I tried with:

ADCIN 13, myvar

because I see channels from 0 to 11 in the DS, maybe "0,6 V ref" would be the 13th...and PBP accepts the compilation but the ADCIN result shows always 0

[Ioannis]

ADCIN x, myvar

where x is the AD channel where you connected the voltage divider we were talking before.

If it is on pin 18, channel 1 then x=1 and so on.

Ioannis

[flotulopex]

I'm sorry, but I still don't understand

Looking at the ADC bloc diagram I've attached in post#1, I understand there is a "0,6V Reference" channel that I have to select to get an ADCIN result of 122 @ 5VDC or 186 @ 3,3VDC.

This channel doesn't seem to be linked to any pin of the PIC - this is confusing me at most.

Does this "0,6V Reference" channel really exist?

----

Hum...just found I have to ENABLE the 0,6Voltage Reference in VRCON register, bit 4 "VP6EN". I'll have a try in a moment...

[flotulopex]

...no, still getting 0.

[Ioannis]

Please post the program.

Ioannis

[flotulopex]

This is the code of which I removed the "cooking timer" specific code placed after the DEBUG part. If you think it can help, I'll post the full code.

'-------------------------------------------------------------------------------
' PIC 16F690 Fuses (MPASM)
@ __config _FCMEN_OFF &_IESO_OFF &_CPD_OFF &_WDT_OFF &_HS_OSC &_BOR_OFF &_CP_OFF &_PWRTE_OFF &_MCLRE_OFF
'_INTRC_OSC_NOCLKOUT

'-------------------------------------------------------------------------------
' Registers   76543210
OPTION_REG = %10000110 'Pull-Ups OFF, Prescaler TMR0 1:128
ANSEL      = %00010000 'Select analog inputs Channels 0 to 7
ANSELH     = %00000000 'Select analog inputs Channels 8 to 11
WPUA       = %00000000 'Select weak pull-ups
WPUB       = %00000000 'Select weak pull-ups
ADCON0     = %10000001 'AD Module is ON, Channel 1
ADCON1     = %00000000 'AD control register
CM1CON0    = %00000000 'Comparator1 Module is OFF
CM2CON0    = %00000000 'Comparator2 Module is OFF
INTCON     = %10100000 'INTerrupts CONtrol; GIE=1, T0IE=1
TRISA      = %00000000 'Select Input/Output (0 to 5)
PORTA      = %00000000 'Set High/Low (0 to 5)
TRISB      = %00110000 'Select Input/Output (4 to 7)
PORTB      = %00000000 'Set High/Low (4 to 7)
TRISC      = %00000001 'Select Input/Output (0 to 7)
PORTC      = %00000000 'Set High/Low (0 to 7)

'-------------------------------------------------------------------------------
' Defines
define OSC 8

DEFINE LCD_DREG PORTC  'LCD data port 
DEFINE LCD_DBIT 4      'LCD data starting PORT.bit (0 or 4)
DEFINE LCD_RSREG PORTC 'LCD register select port 
DEFINE LCD_RSBIT 3     'LCD register select bit 
DEFINE LCD_EREG PORTC  'LCD enable port 
DEFINE LCD_EBIT 2      'LCD enable bit 
DEFINE LCD_BITS 4      'LCD bus size 4 or 8

DEFINE ADC_BITS 10     'Number of bits in ADCIN result

'-------------------------------------------------------------------------------
' Init display

' ELECTRONIC ASSEMBLY DOGM081 LCD display Mandatory settings
'  See datasheet for circuitry changes by 5V or 3,3V operation
pause 1000      'Time to settle Vdd (THIS IS CRUCIAL!!!)
lcdout $FE, $29 'Function Set: 4 bits bus mode
lcdout $FE, $1C 'Bias set
lcdout $FE, $52 'Power control + Contrast (HiByte)(for 5V=$52 or 3,3V=55)
lcdout $FE, $69 'Follower control (5V=$69/3,3V=6D)
Lcdout $FE, $78 'Contrast (LowByte)

' Custom Characters
lcdout $FE,$28 'Function Set change - ONLY valid for ST7036 controller based LCDs
LCDOUT $FE,$40,$02,$06,$1A,$1A,$1A,$06,$02,$00 'Char 0 = Speaker
LCDOUT $FE,$48,$00,$0A,$0A,$00,$00,$11,$0E,$00 'Char 1 = Smile
LCDOUT $FE,$50,00,00,00,00,00,00,00,00 'Char 2
LCDOUT $FE,$58,14,27,17,17,17,17,31,00 'Char 3 = Battery 1/5 full
LCDOUT $FE,$60,14,27,17,17,17,31,31,00 'Char 4 = Battery 2/5 full
LCDOUT $FE,$68,14,27,17,17,31,31,31,00 'Char 5 = Battery 3/5 full
LCDOUT $FE,$70,14,27,17,31,31,31,31,00 'Char 6 = Battery 4/5 full
LCDOUT $FE,$78,14,31,31,31,31,31,31,00 'Char 7 = Battery 5/5 full
lcdout $FE,$29 'Function Set change

'-------------------------------------------------------------------------------
' Variables

CLEAR

SoftSwitch  var PORTA.2
SoftSwitch  = 1
Btn1xMinute var PORTB.4
Btn5xMinute var PORTB.5

'******* DEBUG ******
LED_Alarm   var PORTB.6
LED_Alarm   = 0
LED_RUN     var PORTB.7
LED_RUN     = 0
'******* DEBUG ******

Bat_Enable  var PORTC.1
Bat_Enable  = 0
Bat_Port    var BYTE
Bat_Port    = 4  'PORTC.0 - AN4
Bat_Level   var byte 'for LCD character selection (3:7)
Bat_Level   = 7
Bat_Value   var word 'holds ADC value
Bat_Value   = 0
Minutes     var byte
minutes     = 0
Seconds     var byte
Seconds     = 0
Ticks       var byte
Ticks       = 0
Dsp_Upd     var bit 'Display Update Allowance 
DSP_Upd     = 1
Alarm       var bit
Alarm       = 0
Cnt_A       var word
Cnt_a       = 0
RUN         var bit 'timer is running
RUN         = 0
IdleCounter var byte 'counter that increments while timer is 00:00
IdleCounter = 0

'-------------------------------------------------------------------------------
' Start program


'******* DEBUG ******
TEST:
        ADCIN 13, Bat_value
        lcdout $FE,2,"B ",dec4 Bat_Value
GOTO TEST
'******* DEBUG ******

END

My question, in other words, is: how do I route the VP6 (0,6V Reference) to the ADCIN?

[Ioannis]

Hi Roger.

I am looking now the latest Data sheet (version F) of the chip and it seems that this chip supports 0,6 Volt reference only for the comparator. The ADC can be referenced internally byt the VCC or externaly on pin 18.

Sorry for the late detailed reply. It is my fault I did not check the data sheet earlier.

So in your case you have to use the internal reference to Vcc (that is 5V in your case), with ADCON0 set as it is now and read the input on your pin, which I suppose is PortC.0 with the

ADCIN 4,Bat_Value (Not 13 as in your program).

The other option you may have, is to use the comparator, and when the voltage of the divider trips under the reference, to have an interrupt, or just look for the comparator out if it is set. But you cannot have the exact battery value.

Ioannis