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stef
02-19-2007, 04:26 AM
Hi

I'm interested in using the propeller but I still have some questions if the effort of learning the spin language and a whole new way of woking is worth it. ( I 'm using now the sx series fore some projects).

started to read the manual on the propeller and have some litle questions.

I read that thier are 8 cog. CanI understand this that it is the same like 8 seperate processors?? (Seperate but also togeather that they can exchange information.) Is it the same like 8sx chips to do the load??


So all things together. Is thier a paper that lists the 20 charpest items from a propeller in comparison with the sx. ( Or is somebody willing to list some items for me so I can compare the two series.)

Like : speed, functions, i/o, max tempature, ecc...

I have some new projects comming up that need a complete start. (Nothing I done before) So it is for me a breakpoint to start with the propeller.

A restless hbbyist/ingeneer.


Stef

crgwbr
02-19-2007, 05:03 AM
Yes, the propeller has 8 seperate processors that are linked together with a main bus called the hub. You could liken the prop to 8 sx chips in one, although it's better than that, the prop is 32 bit, the sx is 8 bit. 32 bit means that it is capable of floating point calculations amoung other things. Speedwise, a single cog will run at 20 mips, the sx will do 75 mips. The SX48 has 33 I/O's, the prop has 32 (64 in the future). Anyway, I would greatly recommend the prop anyday.

Craig

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Mike Green
02-19-2007, 05:26 AM
The Propeller also can do a lot more at 20 mips than the sx can do at 75 mips if you're trying to do anything more complex than 8 bit logic or arithmetic. This is partly because the Propeller's instructions are more complex than the SX's. The Propeller also has 2 special purpose counters in each cog (processor) that can do things like frequency synthesis, PWM, DAC, and ADC mostly independent of what the cog's doing and at a much higher rate (up to 160 MHz). For example, each cog can produce NTSC or PAL video, modulated onto a 60MHz carrier for reception by a TV. Although a single cog can't generate VGA video much greater than 512 x 240 resolution, several cogs can be synchronized together to produce 1024 x 768, up to 1600 x 1200 resolution. There's not enough main memory to hold a bitmap that large, but a text display will fit.

Bean
02-19-2007, 08:01 AM
Stef,
There are many differences, but really you must explore each and decide which one best fits the project at hand.

The Propeller, has many advantages: Multiprocessors, 32K RAM, video generation, advanced timer/counters, etc
But the SX has the edge on price, and if you already know PBASIC, it has a more familiar programming language (SX/B).

Bean.

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Mike Green
02-19-2007, 08:56 AM
Bean has an excellent point. With the SX28 protoboard priced at $10, it's hard to justify anything else for a task that's well suited to the SX. You can hardly buy a regulator and blank PC board for that price in small quantities and SX/B certainly makes a lot of common tasks much much easier that using assembly language. The Propeller protoboard is $25, well worth the price, but still more costly if you don't need the power of the Propeller.

RobotWorkshop
02-19-2007, 09:15 AM
From working with both of the chips (and I like both of them myself) I think that for some small projects the SX may still be a better fit. Case in point are those projects that need to start up and run immediately as soon as the chip is powered up. The propeller (while a more powerful chip) has a latency upon power-up when it looks to the external EEPROM to copy it's data before it really gets going. On a project i'm just wrapping up that would be an unacceptable delay and the SX handled the task very well. It all fit neatly in an SX28. This is no knock to the propeller as it can do some amazing things that would be beyond what the SX can do.

It's all a matter of figuring out what you want to do and picking the best device (processor wise) for your particular project at the moment. Some may point to the SX as the best option while others will need a propeller or more powerful chip.

Can anyone else add anything about the startup delay on the prop or if there is a way around it?

Bill Henning
02-19-2007, 09:31 AM
Agreed.. but the SX48 protoboard's are also $10 - Irecently bought five, and ten loose SX chips :) mostly to use them as I/O coprocessors for prop projects.

Mike Green said...
Bean has an excellent point. With the SX28 protoboard priced at $10, it's hard to justify anything else for a task that's well suited to the SX. You can hardly buy a regulator and blank PC board for that price in small quantities and SX/B certainly makes a lot of common tasks much much easier that using assembly language. The Propeller protoboard is $25, well worth the price, but still more costly if you don't need the power of the Propeller.

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johnny_b
02-19-2007, 09:29 PM
RobotWorkshop (http://forums.parallax.com/member.php?u=47009), keep it alive with a Li battery in "sleep mode". it may sound stupid, but I used this solution for
many projects, however not Propeller projects, but it should work also.


RobotWorkshop
02-20-2007, 12:16 AM
I suppose adding a small battery would be an option to prevent the startup delay of the propeller and is definitely a good idea to keep in mind for future projects. However, adding a battery or super cap may not always be an option and in that case the startup delay is a concern. I just wanted to point out a case where the SX series may be more suitable than the propeller. If all a project needs is the power of an SX then it's still viable since it can start up faster and costs less.

Robert

stef
02-20-2007, 05:31 AM
Hi

Thanks for all the replys. Because price is no issue for me I think I 'm going to start with some propeller projects. I have some comming up so it is interesting to have a drive in learning the language.

I'll order some chips and a protoboard.

I'm shure I will need some further assistance in my learning the popeller but when the problems begin I can still aske the questions here. Then learning is a chalange.If this can be in the same way I learned the sx (and for that matther also the javeline and the basic stamp) it suites me fine.

Thanks.



Stef