View Full Version : PIC , Basic Stamp , or SX Microcontroller ?
12-07-2006, 11:33 PM
Iam so confused·about these three types of microcontrollers.
I Would like to know what are differences between them , the capabilities,limitations, and applications of each type .
Iam asking this because iam quite surprised of the price difference among these items, so there is defintely something other than price.
Appreciate any info.
12-07-2006, 11:59 PM
The PIC came first. It was a simple, but very self-contained microprocessor, which combined eeprom and RAM on a single device. It was programmed in PIC assembly language, or by some 'development system', which would take a high-level language like PIC-Basic or Pascal or C, and compile that to PIC assembly language.
Then Parallax had the brilliant idea to package a PIC, an EEPROM, a voltage regulator, and a clock chip into a single 24-pin module. The PIC (a 16C57) was programmed with a PBasic 'interpreter'. When connected to a PC running the Parallax IDE, this device could be programmed in PBasic, the program downloaded to the EEPROM, and the program run. This avoided any special download system a native PIC would require.
Because it's now "interpreted", what actually gets downloaded is a 'tokenized' version of your program -- each PBasic keyword gets converted into an integer. That integer then 'selects' a routine to be run from the PIC to implement that keyword. This is very space efficient, but not very speed efficient. Thus a 'native' PIC can run at 20 Mhz and execute 5 million PIC assembly instructions per second, but the BS2 runs at 2000 PBasic instructions per second.
This is not a huge problem, as 2000 instructions per second is very often "fast enough", and the BS2 is MUCH easier to use.
Now, the SX was a PIC-clone chip, built for raw speed. Its native clock cycle is 50 Mhz. And the chip has been engineered so it can execute 50 million SX assembly instructions per second.
So, there you go. The native PIC is quite nice, but requires $500 or so of hardware and software to program it. The BS2 is very simple and easy to understand, costs $100 for both chip and board to plug it into (the IDE is a free download). For this ease and flexibility you trade off some speed.
And the SX is the speed demon of the three. Parallax has several packages that make it cost less than the BS2, and the SX/Basic makes it almost as easy to program as the BS2. But most people starting out don't need that speed, and the learning curve can be steep.
12-08-2006, 12:58 AM
I would definatly recomend the BS2 for a beguiner, then after a couple monthees or years with that move up to an SX (and for larger projects, maybe a BS2 & SX). Never use a Pic, it's like paying more for something that does a whole lot less.
Pic: About $500
BS2 w/ BOE: about $100
SX, SX Tech board, and SX Blitzs or Key: $75 - $125
12-08-2006, 01:22 AM
PIC really had the wealth to rapidly deploy a huge array of different chips into industrial markets.·
While Senix-Ubicom had a better idea, it seemed that they moved up to larger chips that they sucessfully continue to·manufacture today in providing leading devices for switching networks.·They never really saw the need to compete head on with Microchip.·Their SX-28 and SX-48 remain superior in many ways to a PIC [With much more memory and more speed, you can reconfigure it through virtual peripherals in software to be a modem, a caller ID chip, a Pulse width modulator, an Analog to Digitial chip, a UART, and much more].
But Microchip seems to be able to reach engineers with conviences. And since it all started with PICs, many hobbyist have remained loyal to them even though there is better product.
Parallax realized an educational market existed·and moved to the SX chips because they were both better hardware and a better platform for learning.· With a PIC, you buy a UART;with an SX you fashion your own in software.
So, I would say, 'Stick with Parallax if you want to learn.'· Microchip will never give you the kind of support that a complete beginner needs.· They service big companies for volume sales.· They will never get into the depths of what is really possible with software, they rather fit you with a less versitle chip that can help you quickly consume thousands.· It is quite a different business philosophy.
If you want or need to save money, the SX-28 is a $3 chip with a $10 development board.· IT can be programmed in SX/B, a version of Basic.
If you think that is still too complex, buy a BOE Robot kit or the What's a Microcontroller package.· One of the most important principles of education is to get down to the level of the learner and then help them move up.·
With PICs, you may feel the Lone Ranger without Tonto.
With Parallax, it is about fun and challange.
And what you learn here can only improve PIC programing if you really want to move over to that platform.
"If you want more fiber, eat the package.· Not enough?· Eat the manual."········
···················· Tropical regards,····· G. Herzog [·黃鶴 ]·in Taiwan
Post Edited (Kramer) : 12/7/2006 5:27:45 PM GMT
12-08-2006, 02:03 AM
The PIC developer prices listed above are exagerated. The PicBasic Standard compiler will run you $100 and a PIC programmer will run you $50 for a good third party programmer to $100 for a MELabs programmer. There is a wealth of info on the Microchip's PIC chip but a lot of it is geared more to the professional developer and not the hobbyist level. The hobbyist market is where Parallax really excels - and Parallax makes it very easy to get started as they've posted virtually all their documentation online and you can download it for free.
If you're looking for a processor that has interrupts and can process information very quickly - the SX processor is a good place to start.
If you're looking for a processor to control a robot, the Basic Stamp 2 is a good place to start.
12-08-2006, 02:16 AM
Tsk, Forrest, you left out the cost of a development board to plug the PIC into, which provides power, a clock chip, and communication lines.
Yes, the $500 was a 'ball-park' figure, and very clever people who already know what they are doing can do it for $200 or so. Unfortunately, to GET clever may cost you, too.
Otherwise, good post.
12-08-2006, 03:21 AM
I'm afraid I have to disagree with you on this one...in the details. While it used to be that you needed a dev board (or at least a few parts and some electronics experience) for PIC work, now, with the self-clocked PICs, all you need is a power supply and a programmer. The programmer prices range from almost free (which requires some good voodoo) up to the MElabs expensive job.
There is no comparison in the ease of use, as has been stated. Parallax as always provided the best support and training in the business...for all of their products, and as you so eloquently stated "GETTING clever will cost you". Thje learning curve for PICs, without the help of a $$$ compiler, can be quite steep...especially if you want to use the more advanced features. And even then, it requires experience to even determine WHICH is the PIC·you really need to use for a specific app.
Truly Understand the Fundamentals and the Path will be so much easier...
Post Edited (Tom Walker) : 12/7/2006 7:26:56 PM GMT
12-08-2006, 04:13 AM
Dear All ,
I would like to take the chance and thank you all for the valuable feedback you provided in the replies to the main topic.
For the time being since i worked for some time with the BS2 , i will consider diving into the SX world , and it is really true that Parallax is offering good lerning stuff.
Wish my best all.