SX18 Questions

Electronegativity

Hi guys, I am just getting started and need a little advice.

I have a very simple project in mind for which the SX18AC/DP would likely be sufficient, but I beleive they are no longer manufactured.

The price makes them attractive but I am a bit worried that I will create a device which will be impossible to manufacture in large numbers.

If you (whoever you are) wouldn't mind answering a few questions then take a crack at these:

1. What is the difference between the SX18AC/DP and the SX18AC75/DP?

2. Will the SX18 continue to be available for the forseeable future.

3. Is there any advantage to using a more advanced chip (like the SX20) for an application where the SX18 has sufficient speed, memory, and I/O capabilities?

4. I noticed that the development board that came with the SXKey starter kit has the same voltage regulator as the Basic Stamp Super Carrier Board. Yet it is rated for only 6-9 V instead of 6-30 V. The reason I ask is because I would like to use a 12 V battery in the final product.

Thanks,
-Alexander

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I wonder if this wire is hot...

Ken Gracey

Dear Alexander:

I'd be pleased to answer your questions on behalf of Parallax and Ubicom.

1. No difference except that the 75s were qualified to run at a higher frequency, even though they are the same die.
2. At the moment that part is discontinued. You can buy them as long as we have them in stock. It is the same die as the SX20/28AC part, so you would likely pay the same for an SX18 if they continued to remain in production (we save only a few cents in packaging a lower pin-count part, otherwise our cost is the same). By far, the most common parts for production are the SX28AC/SS and SX48BD, though the 52 is gaining popularity in production projects. But back to your question, we could reintroduce the SX18AC/DP if a customer committed to a high volume, but the past sales volumes have demonstrated this is not a popular package type. Use the 28 if you can.
3. The only advantages are a few more I/O.
4. You can use a 12V battery in the final product provided you regulate the power supply to the SX Key and SX microcontroller.

Let us know if we can be of further assistance.

Sincerely,

Ken Gracey
Parallax, Inc.

Electronegativity

Thanks Ken.

The other thing I like about the SX18 is that it is physically smaller.

When I put the SX18AC/DP into the SX Tech board and run verify with SX-Key V3.1 I get a message that says "vpp initialization failed".

What doth this signify?

-Alexander

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I wonder if this wire is hot...

Ken Gracey

Alexander,

See Section 2.0 of the datasheet posted here: http://www.parallax.com/dl/docs/prod/sx/sx1828old.pdf. This is the old datasheet for the SX18AC/DP.

The location of the SX18's OSC1, OSC2, MCLR and Vdd pins are different than the SX28AC/DP. Therefore, you can't use the SX Tech Board to program the 18-pin parts. Try using a breadboard and wiring the connections as shown in the datasheet. Then it will program.

Ken Gracey
Parallax, Inc.

Electronegativity

Will do Ken, now I know what that 4-pin thingy that came along with the kit is for

What about the SX20, will it work in the SX Tech board?

I'm also a little confused about "surface-mount" parts.
Is there an adaptor that I can use to stick the SX48BD or SX28SS into a breadboard?

Do you know if those home made circuit board kits they sell at Radio Shack are any good?

Thanks again,
-Alexander

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I wonder if this wire is hot...

Bean

Alexander,
The SX20 is only is surface mount.
Parallax has a SX48 prototype board that is only $9.95 and I hear a SX28 prototype board is coming soon.

As for making PCB, if you have a laser printer I recommend the kit from pulsar http://www.pulsar.gs/PCB/a_Pages/4_Products/5f_Starter_Kit/Starter_Kit.html
you will still need to buy the eching solution from radio shack though.
Bean.

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"SX-Video·Module" Now available from Parallax for only $28.95

http://www.parallax.com/detail.asp?product_id=30012

Product web site: www.sxvm.com

"One experiment is worth a thousand theories"
·

Electronegativity

Thanks Bean, But how do I mount a surface mount chip?

It looks like it has flat feet instead of pins.

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I wonder if this wire is hot...

Bean

Very carefully [noparse];)[/noparse]
No really, with a little practice they are not that hard to solder.
Bean.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
"SX-Video·Module" Now available from Parallax for only $28.95

http://www.parallax.com/detail.asp?product_id=30012

Product web site: www.sxvm.com

"One experiment is worth a thousand theories"
·

LoopyByteloose

I built a separate board to program SX-18s and it really was no hassle. The main thing is that the pins are different from the SX-28. You cannot use the SX-28 board.

The SX-20 is tiny. If you look at the drawing and not the dimensions, you may be fooled into thinking it is about the same size as a DIP. You likely need to buy a commercially printed board to mount it and adapt it to DIP.

When all is said and done, it is cheaper to just go with the SX-28 DIP and leave pins un-used. There are very few applications where you might want less pins and the smaller size [noparse][[/noparse]like R/C airplanes].

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G. Herzog in Taiwan