Compare SX/B with PICAXE

richaj45

For those of you who have used a "PICAXE" chip can you say how it would compare to using a SX chip with SX/B?

cheers,
rich

JonnyMac

After reading about the PICAXE I probably wouldn't use it on a bet. Sure, it's cheap, but it forces you to do things the way it wants them to be done (you can't, for example, reorganize the I/O). SX/B, on the other hand, gives you full control of the SX.

PJMonty

Rich,

I too have not used the PICAXE. However, you can buy an SX-Blitz (to program the SX chips) for $30 and an SX-28 proto-board (fully assembled with chip) for $10 and give the SX a whirl. If you want to program using flowcharts (I have no idea why anyone would want to, but it's an option on the PICAXE), buy the PICAXE and have fun. If you want to program using a programming language like BASIC, either will do it.

The PICAXE appears to be yet another "homage" to the concept of the BAISC Stamp. If you like working in that environment, why not just get a BASIC Stamp? The run of the mill PICAXE parts run at 4 MHz, but they sell faster versions you can run up to 24 MHz. The SX will clock up to 75 MHz. Also, since the PICAXE appears to run some sort of interpreter/decoder (like the BASIC Stamp), you waste a percentage of your clock cycles running the interpreter/decoder. Even when running in SX/B (The free BASIC compiler that comes with the free SX-Key IDE), there is no interpreter/decoder. All your clock cycles go to run your code. I guarantee that the SX running SX/B will out perform the fastest PICAXE by a mile.

If you just want to buy the PICAXE chip (no board, just the chip), it costs about $8.60 (the prices on the site are in British pounds since the company is located in Britain). For only $10.00 you can buy the SX-28 proto board which comes with the chip and everything else pre-assembled. Do you want to buy just a chip, or spend another $1.40 and get a working board?

So, got $40 to play with?

Thanks,
PeterM

SxBlitz: www.parallax.com/Store/Microcontrollers/SXTools/tabid/139/CategoryID/16/List/0/SortField/0/Level/a/ProductID/368/Default.aspx

SX-28 Proto Board: www.parallax.com/Store/Microcontrollers/SXDevelopmentBoards/tabid/141/CategoryID/16/List/0/SortField/0/Level/a/ProductID/399/Default.aspx

LoopyByteloose

The PICAXE is very, very introductory. It is mostly designed to allow you to do a few tutorial tasks. So, you can do a few things, but you will easily outgrow it if you learn anything about microprocessors. I doubt if you will outgrow the SX. Once you master SX/B, there is also SX/C and SASM.

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Forrest

The PICAXE is a low cost alternative to a Basic Stamp. For $10, you can buy (3) PICAXE 08M chips (8 pin chips) that support most of the commands as the BS1. All you need to program it are two resistors connected to an RS-232 port on a PC. www.phanderson.com/ is a good source of info and parts in the US

John Couture

Rich,

I have used both and the Picaxe chips are fun. The 08M is cute because you can generate tones with it. A couple of things to consider:

Picaxe
-- does not have interrupts, the SX handles them without breaking a sweat
-- subroutines are simple gosub and return, no parameter passing, no return parameters.
-- some built in IR commands for responding to a TV remote (for example).
-- some built in commands for controlling a keyboard with only a couple of connections.
-- the readadc10 command allows reading of an analog value (10 bit resolution).
-- it has built in 1-Wire (microlan) commands - handy because with the SX you have to jump through a couple of hoops for this.
-- baud rate is limited to 4800 (or 19.2K if using a 16mhz resonator). The SX, as you see in most programs on this list, run about 38K baud even with a 4mhz resonator. Thus, your power consumption would be less on the SX because it is running at a slower speed. That would be important in a battery operated device.

I'm sure there are many more differences, but again, it depends on the application. This forum, for example, seems a lot more knowledgeable about electronics and seems to have a lot more professional electronics designers. The Picaxe forum is much smaller and has a lot of dedicated people but most of them are in it for the hobby.

My first chip was the BS2, then I went to the Picaxe then I went to the SX. BS2 is an excellent learning tool (great manuals) but too expensive per copy. The Picaxe only has a couple of manuals and I think there is only one commercial book on the chip (by Lincoln). Graduating to the SX was like steping into a stadium of possibilities for me and I am still having fun with it. The Propeller is out of my league for now (my SINGLE processors get out of control enough, I can't imagine what it would be like to have EIGHT processors running around doing their own thing!).

If you are just starting out , get the BS2 kit and work through the "What's a microcontroller" book then start collecting all of the books you can find on the BS2. Each one has a morsel of information that you can use. That is the one thing that no other chip on the market can beat Parallax at. The BS2 is used in more university classrooms simply because it is the easiest to get students up to speed on and resources, for the most part, are free.

On the other hand, you won't find the Picaxe in many classrooms in the U.S. and the sites will be limited.

The SX is centered and very firmly grounded in this forum and on www.sxlist.com. You'll find the SX to be a bigger challenge but the rewards are great because of its capabilities. Once you have mastered the SX, you are well on your way to becomming a "professional" microcontroller programmer and are ready to tackle "C" on a PIC processor or something like that.

Hope this helps.

Picaxe Language Reference: http://www.rev-ed.co.uk/docs/picaxe_manual2.pdf

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John J. Couture

San Diego Miramar College

richaj45

John:

Thanks for the first hand info.

I am a professional ASIC/FPGA type and i keep being amazed how people do such
inovative application with the very limited SX. It has high speed and very low cost
going for it, and that seams to be the magic ingredients for creativity.

Maybe it is its simplicity that keeps it going.

I think the propeller is interesting but i wish they would have made a single cog chip,
running at 100Mhz with 4k words of memory. The cog has a nice instruction set archtecture
it just needs to address more than 513 word of memory and 4k words seams to be a
sweet spot for these applications. The hub concept is very good but it takes expensive
technology to make it as fast as the basic cog.

cheers,
rcih

Zoot

richaj45 -- choice of micros naturally depends on need, cost, etc. But I would add that, in my opinion, part of why you see a lot of creative apps for the SX (and the Prop and Stamps for that matter) is the great support (incl. this forum).

There have been a few of my projects where, *on paper*, a PIC might have been better (and a tad cheaper), but once I threw in more programming hardware and the steeper development curve because of a fragmented support and community structure, it just wasn't worth it. And that's not even taking into account my own personal preference for dealing with independent and/or locally-owned businesses whenever possible...

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John Couture

Rich,

You might want to pop over to the Propeller forum and ask that question about the single cog or the language on another chip. Someone may have a "work around" for you.

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John J. Couture

San Diego Miramar College