ADC1 on 20X2 confusion
- Thread starter pmulvey
- Start date
westaust55
Moderator
This has arisen and been discussed before. You need to use a channel number.
The pin identified b.0 is a predefined symbol with the value 0
The ADC channel No are from 1.
If you put B.0 in directly the PE works it out for you but as a variable you need to have a value 1, 2, 3, etc as the channel number.
Edit:
Also as it is an X2 part do not forget the ADCSETUP as mentioned in the READADC section of manual2
The pin identified b.0 is a predefined symbol with the value 0
The ADC channel No are from 1.
If you put B.0 in directly the PE works it out for you but as a variable you need to have a value 1, 2, 3, etc as the channel number.
Edit:
Also as it is an X2 part do not forget the ADCSETUP as mentioned in the READADC section of manual2
Last edited:
inglewoodpete
Senior Member
The following code is (hacked) from a 20X2 program that I am currently developing. If you use similar syntax, the code should work for you too.
Code:
#PICAXE 20X2
' Port B: I/O
Symbol iZAxis0 = 1 'Leg 18 B.0 ADC1
Symbol oLCD = B.1 'Leg 17 B.1 ADC2 Output to serial LCD
'ymbol <spare> = B.2 'Leg 16 B.2 ADC4
'ymbol <spare> = B.3 'Leg 15 B.3 ADC5
Symbol iXAxis0 = 6 'Leg 14 B.4 ADC6
'
Symbol wZVal = w13 'b26,27
Symbol wXVal = w14 'b28,29
'
Init:'Initialise ADC Inputs
' 5432109876543210 ADC Channel
ADCSetup = %0000000001000010 'Enable only ADC channels 1 & 6 (Pins B.0 & B.4)
'
Main:ReadADC10 iZAxis0, wZVal 'Read the accelerometer Z-Axis value
ReadADC10 iXAxis0, wXVal 'Read the accelerometer X-Axis value
hippy
Ex-Staff (retired)
When the port.pin is used inline in the command the compiler automagically sorts out which actual ADC channel to use. It's only when a symbol is used to specify the channel number of the READADC does the issue arise.
For example, for the 20X2 the ADC channel for pin B.0 ( leg 18 ) is ADC1, so these two are the same ...
ReadAdc 1, b0
Symbol POT_ADC = 1
ReadAdc POT_ADC, b0
The compiler also converts "ReadAdc B.0" to "ReadAdc 1" but this will not happen for the following case -
Symbol POT_ADC = B.0
ReadAdc POT_ADC, b0
The "B.0" has a pin numbering value of "0" so this ends up as "ReadAdc 0" not the "ReadAdc 1" desired. There is no ADC0 so the compiler generates an error.
For example, for the 20X2 the ADC channel for pin B.0 ( leg 18 ) is ADC1, so these two are the same ...
ReadAdc 1, b0
Symbol POT_ADC = 1
ReadAdc POT_ADC, b0
The compiler also converts "ReadAdc B.0" to "ReadAdc 1" but this will not happen for the following case -
Symbol POT_ADC = B.0
ReadAdc POT_ADC, b0
The "B.0" has a pin numbering value of "0" so this ends up as "ReadAdc 0" not the "ReadAdc 1" desired. There is no ADC0 so the compiler generates an error.