Picaxe 18X changed to 18M2 - Now there is a sound problem

[ericr]

After changing over to the new 18M2 from 18X in an existing circuit, the sound has changed from the previous "pure" tone to this distorted sound which sounds like it's modulated with a higher frequency.
I am using the simple "Sound" command in all of it's simplicity.
I thought the 18M2 was supposed to be backward compatible with the 18X.
Has anyone else had the same experience?

 

[westaust55]

Can you please post your program code so that others can check.

 

[ericr]

Below is part of a subroutine for making 2 beeps.

soundon:
let b0 = 1 'turn sound on
sound SOUNDER, (121,5) ' symbol SOUNDER = B.7
pause 140
sound SOUNDER, (121,5)
high LED6
pause 1500
fini:
return

 

[Technical]

The sound command frequency is very slightly different between all the different PICAXE chips due to the varying firmware processing requirements, so when moving from one chip to another you may need to tweak the number slightly, particularly as you are very near the top of the operating range (127 is the highest possible). Sound is really designed for 'beep' noises rather than exact notes - use the tune command instead for that.

 

[ericr]

Thanks,

I'll try a lower frequency (a smaller number), and report back. All I want is a beep.

 

[ericr]

I have now changed the frequency value to 105 (from 121). This gives a sound that is easier to listen to. It is still modulated though...!?