Hey all,
Problem solved. Had to redo all ADC code.
Here is the working code. Maybe this is usefull for the coders here;
-- ok, now let's configure ADC
pin_AN0_direction = input
-- ADCON0 CONFIG
ADCON0_CHS0 = OFF -- Channel at 0 (Bit 0)
ADCON0_CHS1 = OFF -- Channel at 0 (Bit 1)
ADCON0_CHS2 = OFF -- Channel at 0 (Bit 2)
ADCON0_CHS3 = OFF -- Channel at 0 (Bit 3)
-- ADCON1 CONFIG
ADCON1_PCFG0 = OFF -- AN0 as Analog ONLY (Bit 0)
ADCON1_PCFG1 = ON -- AN0 as Analog ONLY (Bit 1)
ADCON1_PCFG2 = ON -- AN0 as Analog ONLY (Bit 2)
ADCON1_PCFG3 = ON -- AN0 as Analog ONLY (Bit 3)
ADCON1_VCFG0 = OFF -- Vref+ at VDD
ADCON1_VCFG1 = OFF -- Vref- at VSS
-- ADCON2 CONFIG
ADCON2_ADCS0 = OFF -- AD Conversion Clock at Fosc/64 (Bit 0)
ADCON2_ADCS1 = ON -- AD Conversion Clock at Fosc/64 (Bit 1)
ADCON2_ADCS2 = ON -- AD Conversion Clock at Fosc/64 (Bit 2)
ADCON2_ACQT0 = ON -- AD Acq. Time at 2xTAD (Bit 0)
ADCON2_ACQT1 = OFF -- AD Acq. Time at 2xTAD (Bit 1)
ADCON2_ACQT2 = OFF -- AD Acq. Time at 2xTAD (Bit 2)
ADCON2_ADFM = ON -- AD Result Justify at Right
--
const word ADC_RSOURCE = 2_500 -- Input Resistance
const byte ADC_TEMP = 85 -- PIC Max.
Temperature
const byte ADC_MAX_TAD = 6 -- (0.8us < TAD <
12.5us as per
-- Datasheet, Pag.
41)
-- AD ACQUISITION TIME (Original VAR: adc_conversion_delay)
-- Tacq = Tamp + Tc + Tcoff
const word tamp = 1 -- (=> 0.2us as per Datasheet, Pag. 30)
const word adc_tc = 2 -- ((TEMP – 25°C)x(0.02 us/°C) => 1.2us as per
Datasheet, Pag. 30))
const word adc_tcoff = 2 -- (-(25 pF)x(1 kohm + 4 kohm +
RSOURCE)xln(0.0004883)
-- => 1.56us as per Datasheet, Pag. 30)
const byte ADC_TACQ = byte(tamp + adc_tc + adc_tcoff)
-- (Original VAR: adc_conversion_delay)
--
var word adc_word -- return value
var byte adc_byte[2] at adc_word -- byte array overlay
--
function adc_read_high_res(byte in adc_chan) return word is
pragma inline
--
-- Original Code has here the Channel and L/R Justifying
-- These parameters are set above...
--
ADCON0_ADON = TRUE -- turn on ADC module
--
for ADC_TACQ loop
_usec_delay(1) -- wait acquisition time
-- Original: _usec_delay(10)
end loop
--
ADCON0_GO = TRUE -- start conversion
while ADCON0_GO == TRUE loop -- wait until conversion
completed
-- Empty loop.
end loop
--
adc_byte[1] = ADRESH -- copy high order bits
adc_byte[0] = ADRESL -- copy low order bits
-- Choosed High Resolution options here, from Original Code...
--
-- Honor 2 * max Tad time. Note the value is not very accurate, but safe.
_usec_delay(2 * ADC_MAX_TAD) -- As per Datasheet, Pag. 29
--
ADCON0_ADON = false -- turn off ADC module
return adc_word -- back to caller
end function
Best regrads,
FS
On Wednesday, September 14, 2022 at 1:43:19 PM UTC+1 flyway38 wrote:
> Hello Vasile,
>
> Thank you for your input.
> About Vref it should be set to VCC (5V) and GND. It's the default anyways
> (by the Datasheet info).
> Have, however, noticed that the ADC initial configuration constants don't
> match with the needed ones.
> EX: ANSEL_ADCS, ADCON0_VCFG, ANSEL_ANS0, etc.. aren't used in ADC lib or
> even in PIC(18F2523) lib.
>
> About convertion time and MAX_TAD, have already tested longer time values
> with no sucess...
> Any more ideas?
> Thanks anyways.
>
> Cheers,
> Filipe Santos.
>
> On Wednesday, September 14, 2022 at 12:57:26 PM UTC+1 vasile wrote:
>
>> If your Vref + is +5V and Vref- is GND, full scale means 4095 at 5V.
>> One issue might appear if acquisition time is too short or you have
>> messed something with references.
>> |Vref+| - |Vref-| >=3V
>>
>> On Tue, Sep 13, 2022 at 4:54 PM flyway38 <[email protected]> wrote:
>>
>>> Hello all,
>>>
>>> New question.
>>> My PIC is reading ok ADC values if below 2.5V (1/2 of range VCC/GND).
>>> It seems like 11bit ADC behaviour.
>>>
>>> My code:
>>> -- ok, now let's configure ADC
>>> -- Step 1: ADC analog input pin setup
>>> const byte ADC_CHANNEL = 0 -- port 0 is analog
>>> input (default)
>>> pin_AN0_direction = input
>>> const byte ANSEL_ANS0 = TRUE -- potmeter connected
>>> to pin_AN0
>>> -- Step 2: Set VDD and VSS as Vref
>>> const byte ADCON0_VCFG = FALSE
>>> -- Step 3: Use Frc as ADC clock
>>> const byte ANSEL_ADCS = 0b110
>>> --
>>> const ADC_RSOURCE = 500 -- Input Resistance
>>> const ADC_TEMP = 20 -- PIC Temperature
>>> -- We want the fastest possible ADC timing, so we specify here the
>>> --const ADC_MIN_TAD = 1
>>> const ADC_MAX_TAD = 10
>>> -- Now we can include the library
>>> include adc
>>> -- And initialize the whole with our parameters
>>> adc_init()
>>>
>>> Inside Forever Loop:
>>> iVal = 0 -- Its a DWord
>>> --
>>> for AdcReadings loop
>>> AdcData = adc_read_high_res(AdcChnn)
>>> iVal = iVal + dword(AdcData)
>>> end loop
>>> --
>>> mVal = word(iVal / dword(AdcReadings))
>>>
>>> Any help would be great.
>>> Thank you very much.
>>>
>>> Kind regrads,
>>> Filipe Santos
>>>
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>>>
>>
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