SILLION BUG issue on ADC and get around required 16F1947 rev 2 silicon

[longpole001]

thanks Darrel,


I have put this code in for the AN4 sensor only , however it seems i will have to do this for other A/D services for this rev of chip ????


your DT_INTS-14.bas is included as part of this code for timer0 , and the variable GIE was already in use ,

timer0 setup as 8ms timer , and this A/D routine is called from it after incrementing counters of timer0 = 5sec duration to do a read of the Voltage level


couple of questions
1. Is the duration of the sample time of 20us seemed long for 1 A/D channel ? as the spec sheet for conversion using FRC is about 1.6us average - a max period of 6uS
2. i thought the sleep instruction ( low power mode ) may need to be issued prior to the conversion starting , or are all commands after a sleep command not actioned till sleep mode is terminated ?
3. as this now monitors the interrupt for sleep to finish , then the duration of this routine must be shorter than any other generated interrupts using DT_INT14 else this will not work ??



the code as it stands now
waiting on a Battery power duration test to complete to see if this works ok

Cheers

Sheldon

Get_volts :
   ADON      VAR ADCON0.0         ; A/D converter Enable
   GoDone    VAR ADCON0.1         ; A/D conversion in progress 
   ADIE      VAR PIE1.6           ; A/D Interrupt Enable
   ADIF      VAR PIR1.6           ; A/D Interrupt Flag
   GIEsave   VAR BIT              ; Saves state of GIE

    
    ADCON0 =  %00010001           ' enable ADC AN4 ,( ADCON1 setup at start of program  , Right Justify, FRC clock  )
   
   y = 0                          ' ensure 0
  While Y < 10                    ' do 10 voltage reads
                                  ' silicon bug in rev2 of 16F1947 , requires ADC to be done in lowpower mode and with FDC osc clock internal 
                                  ' also ADCIN command wont work in sleep mode , interupts exit sleep mode  
        PAUSEUS 20                ; Acquisition time
        GIEsave = GIE             ; Save state of Global Interrupts  ( GIE defined in DT_INTS-14.bas )
        GIE = 0                   ; Disable Global interrupts
        ADON = 0                  ; reset A/D module
        ADON = 1                  ; turn on A/D module
        ADIF = 0                  ; Clear Analog Interrupt Flag
        ADIE = 1                  ; Enable Analog Interrupt
        GoDone = 1                ; Start Analog conversion
        @ SLEEP                   ; go to SLEEP
        ADIE = 0                  ; Disable Analog Interrupt
        GIE = GIEsave             ; Restore Global Interrupt state  ( GIE defined in DT_INTS-14.bas )
        value.HighByte = ADRESH   ; Get A/D result
        value.LowByte  = ADRESL         
           
       ' ADCIN 4 ,Value           ' Leave out for Rev 2 of 16F1947 - Read PortA.5 value into variable , this applies the fixed voltage ref (via ADCON0,ADCON1,FVRCON)
        gosub Average             ' Go do running average of ADC reading
        y = y+1                   ' Increment loop counter
  wend

[Darrel Taylor]

1) If you are only reading 1 channel, you don't need any acquisition time.

2) When you put a PIC to SLEEP, all program execution STOPS.
Some peripherals may continue to operate, but the program will not run again until it wakes up.

3) When you put a PIC to SLEEP, the main oscillator is shut-down.
If you are running TIMER0 from the system clock, it too stops during sleep, and your 8mS periods will be extended.