Re: SOLVED: How can I reduce ADC drift
Ok, thanks.
I've reverted to legacy mode, still using FVR, removed all LCD components, added USART:
Code:#CONFIG __config _CONFIG1, _FEXTOSC_OFF & _RSTOSC_HFINT32 & _CLKOUTEN_OFF & _CSWEN_OFF & _FCMEN_ON __config _CONFIG2, _MCLRE_ON & _PWRTE_OFF & _LPBOREN_OFF & _BOREN_ON & _BORV_LO & _ZCD_OFF & _PPS1WAY_OFF & _STVREN_ON & _DEBUG_OFF __config _CONFIG3, _WDTCPS_WDTCPS_11 & _WDTE_OFF & _WDTCWS_WDTCWS_7 & _WDTCCS_LFINTOSC __config _CONFIG4, _WRT_OFF & _SCANE_available & _LVP_OFF __config _CONFIG5, _CP_OFF & _CPD_OFF #ENDCONFIG DEFINE OSC 32 DEFINE ADC_BITS 10 ' 10-bit Analog to digital DEFINE ADC_SAMPLEUS 50 ' Set sampling time in uS DEFINE HSER_RXREG PORTC DEFINE HSER_RXBIT 7 DEFINE HSER_TXREG PORTC DEFINE HSER_TXBIT 6 DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1 Define HSER_BAUD 115200 DEFINE HSER_CLROERR 1 ' Clear overflow automatically DEFINE HSER_SPBRGH 0 DEFINE HSER_SPBRG 68 ;--- Setup registers ----------------------------------------------------------- BAUDCON.3 = 1 ' Enable 16 bit baudrate generator FVRCON = %10000011 ' FIXED VOLTAGE REFERENCE CONTROL REGISTER ' bit 7 FVREN: Fixed Voltage Reference Enable bit ' ---> 1 = Fixed Voltage Reference is enabled ' bit 1-0 ADFVR<1:0>: ADC FVR Buffer Gain Selection bit ' ---> 11 = ADC FVR Buffer Gain is 4x, (4.096V)(2) ADCON0 = %10000100 ' ADC CONTROL REGISTER 0 ' bit 7 ADON: ADC Enable bit ' ---> 1 = ADC is enabled ' bit 2 ADFRM0: ADC results Format/alignment Selection ' ---> 1 = ADRES and ADPREV data are right-justified ADCON2 = %00000000 ' ADC CONTROL REGISTER 2 ' bit 2-0 ADMD<2:0>: ADC Operating Mode Selection bits(1) ' ---> 000 = Basic (Legacy) mode ADCLK = %00111111 ' ADC CLOCK SELECTION REGISTER ' bit 5-0 ADCCS<5:0>: ADC Conversion Clock Select bits ' ---> 111111 = FOSC/128 ADREF = %00000011 ' ADC REFERENCE SELECTION REGISTER ' bit 4 ADNREF: ADC Negative Voltage Reference Selection bit ' ---> 0 = VREF- is connected to AVSS ' bit 1-0 ADPREF: ADC Positive Voltage Reference Selection bits ' ---> 11 = VREF+ is connected to FVR_buffer 1 ADPCH = %00000000 ' ADC POSITIVE CHANNEL SELECTION REGISTER ' ---> 000000 = ANA0 ANSELA = %00001001 ' Pin A3 = ADC (voltage divider) ' Pin A0 = ADC (B5K) ANSELB = %00000000 ANSELC = %00000000 TRISA = %00001001 ' Pin A3 = ADC input 3 ' Pin A0 = ADC input 0 TRISB = %00000000 ' Pin B7 = ...not available, ICSPDAT ' Pin B6 = ...not available, ICSPCLK TRISC = %11000000 ' Pin C7 = RX *** Datasheet requirement, INPUT *** ' Pin C6 = TX *** Datasheet requirement, INPUT *** ADCinput var WORD ADCdiff var WORD OldADC0 var WORD OldADC3 var WORD Pause 100 ' Let PIC and LCD stabilize ADCinput = 0 : ADCdiff = 0 OldADC0 = 9999 : OldADC3 = 9999 Hserout [ "ADC TEST", _ 10, _ "Initial values = 9999", 10, 10] Mainloop: rem ADC 0 adcin 0, ADCinput : adcin 0, ADCinput if ADCinput < oldADC0 then ADCdiff = oldadc0 - adcinput else ADCdiff = adcinput - oldadc0 endif if ADCinput <> oldADC0 then oldADC0 = ADCinput Hserout [ "B5K pot = ", dec4 ADCinput," diff = ", dec4 ADCdiff, 10] while TXSTA.1 = 0 ' Check TRMT bit wend endif rem ADC 3 adcin 3, ADCinput : adcin 3, ADCinput if ADCinput < oldADC3 then ADCdiff = oldadc3 - adcinput else ADCdiff = adcinput - oldadc3 endif if ADCinput <> oldADC3 then oldADC3 = ADCinput Hserout [ " ", _ "Volt/divider = ", dec4 ADCinput," diff = ", dec4 ADCdiff, 10] while TXSTA.1 = 0 ' Check TRMT bit wend endif GOTO Mainloop end
This is what I get now, variations of 1 and 2 mostly:
Code:ADC TEST Initial values = 9999 B5K pot = 0680 diff = 9319 Volt/divider = 0627 diff = 9372 B5K pot = 0681 diff = 0001 Volt/divider = 0628 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0681 diff = 0001 B5K pot = 0679 diff = 0002 Volt/divider = 0627 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0629 diff = 0002 B5K pot = 0679 diff = 0001 Volt/divider = 0630 diff = 0001 Volt/divider = 0629 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0630 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0629 diff = 0001 Volt/divider = 0628 diff = 0001 Volt/divider = 0629 diff = 0001 Volt/divider = 0628 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0629 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0628 diff = 0001 Volt/divider = 0629 diff = 0001 B5K pot = 0678 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0628 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0629 diff = 0001 B5K pot = 0680 diff = 0002 B5K pot = 0679 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0630 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0678 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0631 diff = 0001 Volt/divider = 0632 diff = 0001 Volt/divider = 0631 diff = 0001 Volt/divider = 0632 diff = 0001 B5K pot = 0677 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0631 diff = 0001 Volt/divider = 0630 diff = 0001 B5K pot = 0677 diff = 0001 B5K pot = 0679 diff = 0002 B5K pot = 0678 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0629 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0628 diff = 0001 Volt/divider = 0629 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0678 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0628 diff = 0001 Volt/divider = 0629 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0628 diff = 0001 Volt/divider = 0627 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0628 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0678 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0627 diff = 0001 Volt/divider = 0628 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0627 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0628 diff = 0001 Volt/divider = 0627 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0626 diff = 0001 B5K pot = 0678 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0678 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0625 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0627 diff = 0002 B5K pot = 0679 diff = 0001 Volt/divider = 0626 diff = 0001 Volt/divider = 0627 diff = 0001 Volt/divider = 0626 diff = 0001 Volt/divider = 0627 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0626 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0678 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0678 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0678 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0678 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0678 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0627 diff = 0001 B5K pot = 0678 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0628 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0627 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0626 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0627 diff = 0001 Volt/divider = 0628 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0627 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0626 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0627 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0626 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0627 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0626 diff = 0001 B5K pot = 0678 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0625 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0626 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0625 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0626 diff = 0001 Volt/divider = 0625 diff = 0001 Volt/divider = 0626 diff = 0001 Volt/divider = 0625 diff = 0001 Volt/divider = 0626 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0625 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0626 diff = 0001 Volt/divider = 0625 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0626 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0625 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0624 diff = 0001 Volt/divider = 0625 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0625 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0624 diff = 0001 Volt/divider = 0625 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0624 diff = 0001 Volt/divider = 0625 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0625 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0624 diff = 0001 Volt/divider = 0625 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0623 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0678 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0625 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0623 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0681 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0681 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0681 diff = 0002 Volt/divider = 0623 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0625 diff = 0001 Volt/divider = 0624 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0624 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0681 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0681 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0681 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0622 diff = 0001 B5K pot = 0681 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0623 diff = 0001 Volt/divider = 0622 diff = 0001 B5K pot = 0681 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0623 diff = 0001 Volt/divider = 0622 diff = 0001 B5K pot = 0681 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0681 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0681 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0681 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0681 diff = 0001 Volt/divider = 0623 diff = 0001 Volt/divider = 0622 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0681 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0681 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0681 diff = 0001 Volt/divider = 0623 diff = 0001 Volt/divider = 0622 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0622 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0681 diff = 0001 Volt/divider = 0622 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0624 diff = 0002 Volt/divider = 0623 diff = 0001 Volt/divider = 0624 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0681 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0623 diff = 0001 Volt/divider = 0624 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0624 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0623 diff = 0001 Volt/divider = 0624 diff = 0001 Volt/divider = 0623 diff = 0001 Volt/divider = 0624 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0624 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0624 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0624 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0624 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 B5K pot = 0679 diff = 0001 Volt/divider = 0622 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0622 diff = 0001 Volt/divider = 0623 diff = 0001 B5K pot = 0679 diff = 0001 B5K pot = 0680 diff = 0001 Volt/divider = 0622 diff = 0001
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