Chip-tuning your Picaxe 28 board in a snappy way

Update: Note that the newer Picaxe models can change a lot by commands like setfreq alone :)


This is only for dummies like myself using Picaxe 28Xx standard board. However, the thinking may also apply to those making their own boards.

Specially if you are doing serial communication to say a LCD display, an Easy Radio module, a dedicated sound chip, your PC or something else.. you may need to change the clock speed with an external resonator.

Resonators cannot be found in my local electronics shop, but they are dirt cheap in the Picaxe shop, so I bought a handfull some time ago - in different speeds. I can recomend that!

Then - if you are using the standard board, you will have to de-solder the resonator on the board.

Instead of just soldering on the alternative resonator, I solder on 3 pins like this:


.. and as you can see on the main picture on this post, I stick them resonators into thingeys, so they can just be interchanged :)

It does not matter which way they turn!

See the basic command setfreq in your manual!

Maybe you could add details
Maybe you could add details on how to replace the resonator with an actual crystal, much more accurate, and still pretty darn cheap.

That would only be possible
That would only be possible if I knew how :stuck_out_tongue:

maybe this way
maybe this way : (check ports 4 and 5) but i’m not sure.

That looks very much like

That looks very much like the overall idea to me, to the level of my understanding :slight_smile:

(Still, I am not going to make any walkthrough on it :P)

My 2-cents worth

Has anyone used crystals before with the 'picaxe?

The approach outlined in the circuit above WILL work for pics. For info, the capacitors CANNOT be left out. But all you need is the crystal and the two caps. I’ve done it with 4MHz, 8MHz, 16MHz and 20MHz. I’ve not come across a pic which is spec’d to work at higher than 20MHz.

All you need is to sodder the doofus (crystal) and the two wotsits (caps) onto the thingy.

POTENTIALLY IMPORTANT NOTE: Does one need to tell the picaxe what type of oscillator is in use? In RISC, it is necessary to tell the pic if a high speed or low speed external or internal, or R/C network is in use. I suspect there’ll be a similar flag to set in the 'axe.

You just tell it if it is
You just tell it if it is internal or external and what speed. Yes, goes up to 20. See command setfreq.

I think you’ll need some

I think you’ll need some sort of adapter. This is the way they’re supposed to be wired to an IC:

A is a standard crystal, while B is a ceramic resonator. You might get away with just wiring the two pins of the crystal to where the two outer pins were on the ceramic resonator.

Good tip

Good tip Fritz! That’s one modification of the board I’m definately going to do.

Also: it took me a while to figure out that you do need that setfreq command. Otherwise the external resonator will simply be ignored.

Where do you purchase the
Where do you purchase the plug things you solder the resonator to? I’ve only ever seen them on servo leads, but I can think of endless uses.

Any electronics store, they
Any electronics store, they are quite standard thingeys!

Apparently not in New
Apparently not in New Zealand… I may have to order in some from a U.S. online store or something. I get most of my parts from,,, and on rare occasions I don’t think any of them stock them.

From Jaycar :
From Jaycar : maybe as close as they have.

Yeah, I use those. They’re
Yeah, I use those. They’re incredibly bulky though.

Might check radio control
Might check radio control stores, where they sell model airplanes and cars. They should stock servo connectors for HiTec that would match very close to what Frits has.

Thanks, I know of a store,
Thanks, I know of a store, I’ll have a look.

It’s as simple as that

Captain Tuna has it in one. It is that simple. Cheers