Getting started with PICAXE

One thing which I’ve come across a few times of late is people who are interested to get into PICAXE’s but they have looked at them in a much to complicated kind of way, I think the one common thread is that these people, like me, have looked at the ‘PIC’ stuff in the JayCar catalog and thought to themselves ‘I might get into these PIC’s etc’.

Let’s be clear.. JAYCAR don’t carry PICAXE or anything that supports PICAXE (apart from common components of course – resistors/breadboards etc) – Yes, I think JayCar are mad!! then would sell truckloads more PICAXE than they ever sell of PIC – and yes, I tell them that every time I go into a store

To set the framework..

• PIC Chips are ‘Microcontrollers’ – as opposed to Microprocessors – there is a big difference, though most people care less to appreciate it. Basically, a PIC or a PICAXE for that matter can be thought of as a tiny computer with limited functions.
• PIC chips are made by a company called ‘MicroChip Technology‘ based out of Arizona – USA
• you can write programs for PIC’s in many different high level languages but people will often write their PIC programs in what’s known as ASSEMBLER code – not for the faint of heart. there is also PICBASIC and C programs to write PIC code in as well – even with those it is STILL A LOT MORE COMPLEX than just going down the PICAXE path.
• PICAXE chips are actually PIC chips which are purchased by a company called Revolution Education(Rev-Ed) based out of Bath(UK), about 155Km west of London, UK. Rev-Ed then install what’s a called a ‘bootloader’ onto the raw PIC chips. The Bootloader can be thought of as a ‘software foundation’ if you like. It takes the chip and transforms it into a much easier to use and program chip.
• There are literally 100′s of PIC chips released by MicroChip – actually, it’s overwhelming!
• the Microchip website is insanely complex to navigate.. just purely because there is SO MUCH stuff! – however, once you appreciate it, it’s a great website – but very confusing for beginners!
• There are much fewer chips released by Rev-Ed as PICAXE’s – they are : [PICAXE]08M, 14M, 18M2, 20X2, 28X2, 40X2  (there are a few more but these are ones you would actually and practically buy today)
• it’s fair to say that a PIC chip (ie no PICAXE bootloader) is much faster and more powerful but really, most people would NEVER need that level of power. PICAXE can do very complex and powerful applications, plus it can run very fast.
• To program a PIC chip you need a special ‘hardware programmer’ as such and the process is a lot more complex(won’t go into that here)
• To write a program and to ‘program’ a PICAXE chip is A LOT easier and all the bits you need are free – details below!
• with PICAXE chips
  • the number – in PICAXE “08″M – means the number of pins. the more pins, the bigger the chip, the bigger the chip the faster if will run(clock speed) and more options you have.
  • the Letter at the end is the ‘generation’ – My understanding is that there was plain, then A, then M, then X, then X1, then X2 and now there is M2 – I may not be totally correct but that’s the essence of it. with different generations came things like more RAM, a few more commands/options etc.
  • Not all commands work on all chips – things like I2C (used for communication between chips) you only get those on upward of the 18X’s. they ALL work on the bigger chips but not ALL commands work on the smaller chips.
  • for a beginner the 08M is quite fine – once you start to know what you’re doing you’ll fall short with the 08M and then go for a 14M or what’s even better now days is the 18M2 – they’re only $5.95AUD! (a 08M is $3.55)
  • it’s NOT foolish to go for a bigger chip up front to start off with – like an 18M2 – all the simple programs and scenarios you would do with a 08M work just as easily on an 18M2 or even a 40X2 for that matter.

Can I just say this – PICAXE’s are simple.. !!!

They’re probably 2-5 times more simple than you had imagined. Writing code is dead easy, even if you haven’t written programs before & downloading your code is super simple.

A analogy might be : You can go to a PC shop and buy a ‘Computer’ per se, you can choose to run Linux as the operating system or perhaps Windows 7, or windows XP. In a some kind of a similar regard PICAXE is just about that different when comparing to a PIC chip. The way you write code, how you interact with the inputs/outputs, the way you program them etc – it’s all different.

I learnt PICAXE first.. and was amazed at the simplicity. Now, I am learning PIC (for fun really) and I am amazed at the complexity!

did I say it – PICAXE is simple..!!!

lets get on with it I hear you say..

Ok, You need just a few things..

1. A Programming Cable. There really is nothing proprietary about this. In it’s simplest form it can be just a standard DB-9 plug connecting to COM1 on your computer and three of those wires are used to program the PICAXE chip(in circuit).

• A Serial Programming Cable – connecting to COM1/Com2 etc (simple, cheap, but you need to have a real COM port, which many of us don’t have these days – ie laptop users) [you can buy one], or you can just make up your own – see the PICAXE manuals(referred to below) – the dead easy option => Take a Serial Mouse with a DB-9 plug on it. Chop the mouse end off.. take the appropriate wires and connect to a 3.5MM stereo plug – simple!
• A USB Programming Cable – (link to AXE027) – I like this one because I don’t need to worry about having to find a PC etc with a real COM port.

2.  You need the PICAXE ‘Programming Editor’ software. In this you write/design your code, you can test it(ie run it in emulation mode) and then you can download the code to your PICAXE using that program and whatever choice you took from option 1 above (Serial or USB programming Cable)

• here is the link to the software from the PICAXE.CO.UK site.

3. The PICAXE Manuals – these are your bibles, everything you need to know will be in one of these three manuals – keep them on your desktop and very handy.

• Manual 1 : Getting Started
• Manual 2 : BASIC commands
• Manual 3 : Interfacing Circuits

4. A Board to program your PICAXE on. To start off with I HIGHLY recommend you buy yourself a AXE092P or if you are planning on buying the USB programming cable also why not buy the combo. Moving forward, if you want to program a PICAXE all you practically need is a 10k and 22k resistor plus a power supply for your PICAXE – like 5Volts from a 7805 reg or perhaps a 3xAA battery pack (making 4.5Vdc). I normally use the 3 x AA option as it’s just so easy!

5. a simple program to load into your PICAXE to test it with! here is one which will work on a PICAXE 08M . it just flashes a LED on and off.. how simple can you get! high 2 means turn on output2 – pin6

main:
high 2
pause 1000
low 2
pause 1000
goto main

I should point out that with PICAXE this code is all you need. You then simply download it to your PICAXE using the programming editor (point 2 above) – there is no need to Assemble/Compile the code etc. the PICAXE bootloader accepts the basic code in just like it appears above. Once your code has downloaded it will commence running.

In various placesd you will see a software CD mentioned/displayed – you don’t need it! – you just need the files I have linked to above.. everything on that CD can be downloaded from the picaxe.co.uk site.

Now, how easy was that..??

if you need help or there are parts which this articles doesn’t explain well enough please drop me a line - vk3jap@vk3jap.net

if you’re in the Australian time zone and would like to tap into other people who are probably doing what you are or have done what you want to do then go jump onto the OzElecForums at http://ozelecforum.com – there is a section dedicated there to PICAXE and people who are quite happy to help out, even with total newbie questions – in fact, they’re encouraged.