Compiler bug?

[Adrian Hudson]

Is it a bug or is it me? (Probably the latter)

The first readadc statement does not work (nothing placed in b0) wheras the second statement works.

#PICAXE 20X2
symbol LDC = B.4
adcsetup = %0000000001000000
readadc LDC,b0 ; This statement does not work
readadc B.4,b0 ; This works

 

[Technical]

When using readadc on X2 parts you must use the channel number, not the pin number. See
http://www.picaxe.com/BASIC-Commands/Analogue-InputOutput/readadc/

If you use the pin number directly the compiler 'intelligently finds' this and auto-corrects your mistake. However it can't auto correct symbols.

See the pin out diagram in the manual to match the ADC channel number to the correct pin.

 

[Adrian Hudson]

See, I said it was my mistake

Thanks Technical
Adrian

 

[KeithRB]

Maybe you should correct the ReadADC example in Manual 2, since it uses the pin number, or at least point out that the example does not apply to X2 parts.

 

[hippy]

@ KeithRB : The "readadc C.1,b1" example in the manual is correct for all parts using port.pin notation.

When the port.pin is used inline in the command as here 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 C.2 ( leg 8 ) is ADC8, so these two are the same ...

ReadAdc 8, b0

Symbol POT_ADC = 8
ReadAdc POT_ADC, b0

The compiler also converts "ReadAdc C.2" to "ReadAdc 8" but this will not happen for the following case -

Symbol POT_ADC = C.2
ReadAdc POT_ADC, b0

The "C.2" has a pin numbering value of "10" so this ends up as "ReadAdc 10" not the "ReadAdc 8" desired.

 

[KeithRB]

I understand completely, but the example completely glosses over that the *channel* is required, not strictly the port.pin.

For example, the ReadADC10 command contains this caveat:
"On X2 parts you must use the ADC channel, not the pin number, in the readadc
command (e.g. readadc10 0,w1 NOT readadc10 A.0, w1)"

 

[hippy]

For example, the ReadADC10 command contains this caveat:

Got you! Sorry for misunderstanding. I've made a note that this caveat isn't also in the READADC command text.

 

[KeithRB]

Actually, the caveat seems to be worded a bit too strongly, given the compiler magic.